x11vnc: allow VNC connections to real X11 displays. 0.9.17 lastmod: 2025-04-11
(type "x11vnc -opts" to just list the options.)
Typical usage is:
Run this command in a shell on the remote machine "far-host"
with X session you wish to view:
x11vnc -display :0
Then run this in another window on the machine you are sitting at:
vncviewer far-host:0
Once x11vnc establishes connections with the X11 server and starts listening
as a VNC server it will print out a string: PORT=XXXX where XXXX is typically
5900 (the default VNC server port). One would next run something like
this on the local machine: "vncviewer hostname:N" where "hostname" is
the name of the machine running x11vnc and N is XXXX - 5900, i.e. usually
"vncviewer hostname:0".
By default x11vnc will not allow the screen to be shared and it will exit
as soon as the client disconnects. See -shared and -forever below to override
these protections. See the FAQ for details how to tunnel the VNC connection
through an encrypted channel such as ssh(1). In brief:
ssh -t -L 5900:localhost:5900 far-host 'x11vnc -localhost -display :0'
vncviewer -encodings 'copyrect tight zrle hextile' localhost:0
Also, use of a VNC password (-rfbauth or -passwdfile) is strongly recommended.
For additional info see: http://www.karlrunge.com/x11vnc/
and http://www.karlrunge.com/x11vnc/faq.html
Config file support: if the file $HOME/.x11vncrc exists then each line in
it is treated as a single command line option. Disable with -norc. For
each option name, the leading character "-" is not required. E.g. a line
that is either "forever" or "-forever" may be used and are equivalent.
Likewise "wait 100" or "-wait 100" are acceptable and equivalent lines.
The "#" character comments out to the end of the line in the usual way
(backslash it for a literal). Leading and trailing whitespace is trimmed off.
Lines may be continued with a "\" as the last character of a line (it
becomes a space character).
Options:
-display disp X11 server display to connect to, usually :0. The X
server process must be running on same machine and
support MIT-SHM. Equivalent to setting the DISPLAY
environment variable to "disp".
See the description below of the "-display WAIT:..."
extensions, where alias "-find" will find the user's
display automatically, and "-create" will create a
Xvfb session if no session is found.
-auth file Set the X authority file to be "file", equivalent to
setting the XAUTHORITY environment variable to "file"
before startup. Same as -xauth file. See Xsecurity(7),
xauth(1) man pages for more info.
Use '-auth guess' to have x11vnc use its -findauth
mechanism (described below) to try to guess the
XAUTHORITY filename and use it.
XDM/GDM/KDM: if you are running x11vnc as root and want
to find the XAUTHORITY before anyone has logged into an
X session yet, use: x11vnc -env FD_XDM=1 -auth guess ...
(This will also find the XAUTHORITY if a user is already
logged into the X session.) When running as root,
FD_XDM=1 will be tried if the initial -auth guess fails.
-N If the X display is :N, try to set the VNC display to
also be :N This just sets the -rfbport option to 5900+N
The program will exit immediately if that port is not
available. The -N option only works with normal -display
usage, e.g. :0 or :8, -N is ignored in the -display
WAIT:..., -create, -find, -svc, -redirect, etc modes.
-autoport n Automatically probe for a free VNC port starting at n.
The default is to start probing at 5900. Use this to
stay away from other VNC servers near 5900.
-rfbport str The VNC port to listen on (a LibVNCServer option), e.g.
5900, 5901, etc. If specified as "-rfbport PROMPT"
then the x11vnc -gui is used to prompt the user to
enter the port number.
-6 IPv6 listening support. In addition to IPv4, the
IPv6 address is listened on for incoming connections.
The same port number as IPv4 is used.
NOTE: This x11vnc binary was compiled to have the
"-6" IPv6 listening mode ENABLED by default (CPPFLAGS
-DX11VNC_LISTEN6=1). So to disable IPv6 listening mode
you MUST supply the "-no6" option (see below.)
The "-6" mode works for both normal connections and
-ssl encrypted ones. Nearly everything is supported
for the IPv6 case, but there are a few exceptions.
See -stunnel for its IPv6 support.
Currently, for absolutely everything to work correctly
the machine may need to have some IPv4 support, at the
least for the loopback interface. However, for nearly
all usage modes no IPv4 support is required. See -noipv4.
If you have trouble compiling or running in IPv6 mode,
set -DX11VNC_IPV6=0 in CPPFLAGS when configuring to
disable IPv6 support.
-no6 Disable IPv6 listening support (only useful if the
"-6" mode is compiled in to be the default; see the
X11VNC_LISTEN6 description above under "-6".)
-noipv6 Do not try to use IPv6 for any listening or connecting
sockets. This includes both the listening service
port(s) and outgoing connections from -connect,
-connect_or_exit, or -proxy. Use this if you are having
problems due to IPv6.
-noipv4 Do not try to use IPv4 for any listening or connecting
sockets. This is mainly for exploring the behavior of
x11vnc on an IPv6-only system, but may have other uses.
-reopen If the X server connection is disconnected, try to
reopen the X display (up to one time.) This is of use
for display managers like GDM (KillInitClients option)
that kill x11vnc just after the user logs into the
X session. Note: the reopened state may be unstable.
Set X11VNC_REOPEN_DISPLAY=n to reopen n times and
set X11VNC_REOPEN_SLEEP_MAX to the number of seconds,
default 10, to keep trying to reopen the display (once
per second.)
Update: as of 0.9.9, x11vnc tries to automatically avoid
being killed by the display manager by delaying creating
windows or using XFIXES. So you shouldn't need to use
KillInitClients=false as long as you log in quickly
enough (within 45 seconds of connecting.) You can
disable this by setting X11VNC_AVOID_WINDOWS=never.
You can also set it to the number of seconds to delay.
-reflect host:N Instead of connecting to and polling an X display,
connect to the remote VNC server host:N and be a
reflector/repeater for it. This is useful for trying
to manage the case of many simultaneous VNC viewers
(e.g. classroom broadcasting) where, e.g. you put
a repeater on each network switch, etc, to improve
performance by distributing the load and network
traffic. Implies -shared (use -noshared as a later
option to disable). See the discussion below under
-rawfb vnc:host:N for more details.
-id windowid Show the X window corresponding to "windowid" not
the entire display. New windows like popup menus,
transient toplevels, etc, may not be seen or may be
clipped. Disabling SaveUnders or BackingStore in the
X server may help show them. x11vnc may crash if the
window is initially partially obscured, changes size,
is iconified, etc. Some steps are taken to avoid this
and the -xrandr mechanism is used to track resizes. Use
xwininfo(1) to get the window id, or use "-id pick"
to have x11vnc run xwininfo(1) for you and extract
the id. The -id option is useful for exporting very
simple applications (e.g. the current view on a webcam).
-sid windowid As -id, but instead of using the window directly it
shifts a root view to it: this shows SaveUnders menus,
etc, although they will be clipped if they extend beyond
the window.
-appshare Simple application sharing based on the -id/-sid
mechanism. Every new toplevel window that the
application creates induces a new viewer window via
a reverse connection. The -id/-sid and -connect
options are required. Run 'x11vnc -appshare -help'
for more info.
-clip WxH+X+Y Only show the sub-region of the full display that
corresponds to the rectangle geometry with size WxH and
offset +X+Y. The VNC display has size WxH (i.e. smaller
than the full display). This also works for -id/-sid
mode where the offset is relative to the upper left
corner of the selected window. An example use of this
option would be to split a large (e.g. Xinerama) display
into two parts to be accessed via separate viewers by
running a separate x11vnc on each part.
Use '-clip xinerama0' to clip to the first xinerama
sub-screen (if xinerama is active). xinerama1 for the
2nd sub-screen, etc. This way you don't need to figure
out the WxH+X+Y of the desired xinerama sub-screen.
screens are sorted in increasing distance from the
(0,0) origin (I.e. not the Xserver's order).
-flashcmap In 8bpp indexed color, let the installed colormap flash
as the pointer moves from window to window (slow).
Also try the -8to24 option to avoid flash altogether.
-shiftcmap n Rare problem, but some 8bpp displays use less than 256
colorcells (e.g. 16-color grayscale, perhaps the other
bits are used for double buffering) *and* also need to
shift the pixels values away from 0, .., ncells. "n"
indicates the shift to be applied to the pixel values.
To see the pixel values set DEBUG_CMAP=1 to print out
a colormap histogram. Example: -shiftcmap 240
-notruecolor For 8bpp displays, force indexed color (i.e. a colormap)
even if it looks like 8bpp TrueColor (rare problem).
-advertise_truecolor If the X11 display is indexed color, lie to clients
when they first connect by telling them it is truecolor.
To workaround RealVNC: inPF has colourMap but not 8bpp
Use '-advertise_truecolor reset' to reset client fb too.
-visual n This option probably does not do what you think.
It simply *forces* the visual used for the framebuffer;
this may be a bad thing... (e.g. messes up colors or
cause a crash). It is useful for testing and for some
workarounds. n may be a decimal number, or 0x hex.
Run xdpyinfo(1) for the values. One may also use
"TrueColor", etc. see <X11/X.h> for a list. If the
string ends in ":m" then for better or for worse
the visual depth is forced to be m. You may want to
use -noshm when using this option (so XGetImage may
automatically translate the pixel data).
-overlay Handle multiple depth visuals on one screen, e.g. 8+24
and 24+8 overlay visuals (the 32 bits per pixel are
packed with 8 for PseudoColor and 24 for TrueColor).
Currently -overlay only works on Solaris via
XReadScreen(3X11) and IRIX using XReadDisplay(3).
On Solaris there is a problem with image "bleeding"
around transient popup menus (but not for the menu
itself): a workaround is to disable SaveUnders
by passing the "-su" argument to Xsun (in
/etc/dt/config/Xservers).
Use -overlay as a workaround for situations like these:
Some legacy applications require the default visual to
be 8bpp (8+24), or they will use 8bpp PseudoColor even
when the default visual is depth 24 TrueColor (24+8).
In these cases colors in some windows will be incorrect
in x11vnc unless -overlay is used. Another use of
-overlay is to enable showing the exact mouse cursor
shape (details below).
Under -overlay, performance will be somewhat slower
due to the extra image transformations required.
For optimal performance do not use -overlay, but rather
configure the X server so that the default visual is
depth 24 TrueColor and try to have all apps use that
visual (e.g. some apps have -use24 or -visual options).
-overlay_nocursor Sets -overlay, but does not try to draw the exact mouse
cursor shape using the overlay mechanism.
-8to24 [opts] Try this option if -overlay is not supported on your
OS, and you have a legacy 8bpp app that you want to
view on a multi-depth display with default depth 24
(and is 32 bpp) OR have a default depth 8 display with
depth 24 overlay windows for some apps. This option
may not work on all X servers and hardware (tested
on XFree86/Xorg mga driver and Xsun). The "opts"
string is not required and is described below.
This mode enables a hack where x11vnc monitors windows
within 3 levels from the root window. If it finds
any that are 8bpp it extracts the indexed color
pixel values using XGetImage() and then applies a
transformation using the colormap(s) to create TrueColor
RGB values that it in turn inserts into bits 1-24 of
the framebuffer. This creates a depth 24 "view"
of the display that is then exported via VNC.
Conversely, for default depth 8 displays, the depth
24 regions are read by XGetImage() and everything is
transformed and inserted into a depth 24 TrueColor
framebuffer.
Note that even if there are *no* depth 24 visuals or
windows (i.e. pure 8bpp), this mode is potentially
an improvement over -flashcmap because it avoids the
flashing and shows each window in the correct color.
This method works OK, but may still have bugs and it
does hog resources. If there are multiple 8bpp windows
using different colormaps, one may have to iconify all
but one for the colors to be correct.
There may be painting errors for clipping and switching
between windows of depths 8 and 24. Heuristics are
applied to try to minimize the painting errors. One can
also press 3 Alt_L's in a row to refresh the screen
if the error does not repair itself. Also the option
-fixscreen 8=3.0 or -fixscreen V=3.0 may be used to
periodically refresh the screen at the cost of bandwidth
(every 3 sec for this example).
The [opts] string can contain the following settings.
Multiple settings are separated by commas.
For for some X servers with default depth 24 a
speedup may be achieved via the option "nogetimage".
This enables a scheme were XGetImage() is not used
to retrieve the 8bpp data. Instead, it assumes that
the 8bpp data is in bits 25-32 of the 32bit X pixels.
There is no requirement that the X server should put
the data there for our poll requests, but some do and
so the extra steps to retrieve it can be skipped.
Tested with mga driver with XFree86/Xorg. For the
default depth 8 case this option is ignored.
To adjust how often XGetImage() is used to poll the
non-default visual regions for changes, use the option
"poll=t" where "t" is a floating point time.
(default: 0.05)
Setting the option "level2" will limit the search
for non-default visual windows to two levels from the
root window. Do this on slow machines where you know
the window manager only imposes one extra window between
the app window and the root window.
Also for very slow machines use "cachewin=t"
where t is a floating point amount of time to cache
XGetWindowAttributes results. E.g. cachewin=5.0.
This may lead to the windows being unnoticed for this
amount of time when deiconifying, painting errors, etc.
While testing on a very old SS20 these options gave
tolerable response: -8to24 poll=0.2,cachewin=5.0. For
this machine -overlay is supported and gives better
response.
Debugging for this mode can be enabled by setting
"dbg=1", "dbg=2", or "dbg=3".
-24to32 Very rare problem: if the framebuffer (X display
or -rawfb) is 24bpp instead of the usual 32bpp, then
dynamically transform the pixels to 32bpp. This will be
slower, but can be used to work around problems where
VNC viewers cannot handle 24bpp (e.g. "main: setPF:
not 8, 16 or 32 bpp?"). See the FAQ for more info.
In the case of -rawfb mode, the pixels are directly
modified by inserting a 0 byte to pad them out to 32bpp.
For X displays, a kludge is done that is equivalent to
"-noshm -visual TrueColor:32". (If better performance
is needed for the latter, feel free to ask).
-scale fraction Scale the framebuffer by factor "fraction". Values
less than 1 shrink the fb, larger ones expand it. Note:
the image may not be sharp and response may be slower.
If "fraction" contains a decimal point "." it
is taken as a floating point number, alternatively
the notation "m/n" may be used to denote fractions
exactly, e.g. -scale 2/3
To scale asymmetrically in the horizontal and vertical
directions, specify a WxH geometry to stretch to:
e.g. '-scale 1024x768', or also '-scale 0.9x0.75'
Scaling Options: can be added after "fraction" via
":", to supply multiple ":" options use commas.
If you just want a quick, rough scaling without
blending, append ":nb" to "fraction" (e.g. -scale
1/3:nb). No blending is the default for 8bpp indexed
color, to force blending for this case use ":fb".
To disable -scrollcopyrect and -wirecopyrect under
-scale use ":nocr". If you need to to enable them use
":cr" or specify them explicitly on the command line.
If a slow link is detected, ":nocr" may be applied
automatically. Default: :cr
More esoteric options: for compatibility with vncviewers
the scaled width is adjusted to be a multiple of 4:
to disable this use ":n4". ":in" use interpolation
scheme even when shrinking, ":pad" pad scaled width
and height to be multiples of scaling denominator
(e.g. 3 for 2/3).
-geometry WxH Same as -scale WxH
-scale_cursor frac By default if -scale is supplied the cursor shape is
scaled by the same factor. Depending on your usage,
you may want to scale the cursor independently of the
screen or not at all. If you specify -scale_cursor
the cursor will be scaled by that factor. When using
-scale mode to keep the cursor at its "natural" size
use "-scale_cursor 1". Most of the ":" scaling
options apply here as well.
-viewonly All VNC clients can only watch (default off).
-shared VNC display is shared, i.e. more than one viewer can
connect at the same time (default off).
-once Exit after the first successfully connected viewer
disconnects, opposite of -forever. This is the Default.
-forever Keep listening for more connections rather than exiting
as soon as the first client(s) disconnect. Same as -many
To get the standard non-shared VNC behavior where when
a new VNC client connects the existing VNC client is
dropped use: -nevershared -forever This method can
also be used to guard against hung TCP connections that
do not go away.
-loop Create an outer loop restarting the x11vnc process
whenever it terminates. -bg and -inetd are ignored
in this mode (however see -loopbg below).
Useful for continuing even if the X server terminates
and restarts (at that moment the process will need
permission to reconnect to the new X server of course).
Use, e.g., -loop100 to sleep 100 millisecs between
restarts, etc. Default is 2000ms (i.e. 2 secs) Use,
e.g. -loop300,5 to sleep 300 ms and only loop 5 times.
If -loopbg (plus any numbers) is specified instead,
the "-bg" option is implied and the mode approximates
inetd(8) usage to some degree. In this case when
it goes into the background any listening sockets
(i.e. ports 5900, 5800) are closed, so the next one
in the loop can use them. This mode will only be of
use if a VNC client (the only client for that process)
is already connected before the process goes into the
background, for example, usage of -display WAIT:..,
-svc, and -connect can make use of this "poor man's"
inetd mode. The default wait time is 500ms in this
mode. This usage could use useful: -svc -bg -loopbg
-timeout n Exit unless a client connects within the first n seconds
after startup.
If there have been no connection attempts after n
seconds x11vnc exits immediately. If a client is
trying to connect but has not progressed to the normal
operating state, x11vnc gives it a few more seconds
to finish and exits if it does not make it to the
normal state.
For reverse connections via -connect or -connect_or_exit
a timeout of n seconds will be set for all reverse
connects. If the connect timeout alarm goes off,
x11vnc will exit immediately.
-sleepin n At startup sleep n seconds before proceeding (e.g. to
allow redirs and listening clients to start up)
If a range is given: '-sleepin min-max', a random value
between min and max is slept. E.g. '-sleepin 0-20' and
'-sleepin 10-30'. Floats are allowed too.
-inetd Launched by inetd(8): stdio instead of listening socket.
Note: if you are not redirecting stderr to a log file
(via shell 2> or -o option) you MUST also specify the -q
option, otherwise the stderr goes to the viewer which
will cause it to abort. Specifying both -inetd and -q
and no -o will automatically close the stderr.
-tightfilexfer Enable the TightVNC file transfer extension. Note that
that when the -viewonly option is supplied all file
transfers are disabled. Also clients that log in
viewonly cannot transfer files. However, if the remote
control mechanism is used to change the global or
per-client viewonly state the filetransfer permissions
will NOT change.
IMPORTANT: please understand if -tightfilexfer is
specified and you run x11vnc as root for, say, inetd
or display manager (gdm, kdm, ...) access and you do
not have it switch users via the -users option, then
VNC Viewers that connect are able to do filetransfer
reads and writes as *root*.
Also, tightfilexfer is disabled in -unixpw mode.
-ultrafilexfer Note: to enable UltraVNC filetransfer and to get it to
work you probably need to supply these LibVNCServer
options: "-rfbversion 3.6 -permitfiletransfer"
"-ultrafilexfer" is an alias for this combination.
IMPORTANT: please understand if -ultrafilexfer is
specified and you run x11vnc as root for, say, inetd
or display manager (gdm, kdm, ...) access and you do
not have it switch users via the -users option, then
VNC Viewers that connect are able to do filetransfer
reads and writes as *root*.
Note that sadly you cannot do both -tightfilexfer and
-ultrafilexfer at the same time because the latter
requires setting the version to 3.6 and tightvnc will
not do filetransfer when it sees that version number.
-http Instead of using -httpdir (see below) to specify
where the Java vncviewer applet is, have x11vnc try
to *guess* where the directory is by looking relative
to the program location and in standard locations
(/usr/local/share/x11vnc/classes, etc). Under -ssl or
-stunnel the ssl classes subdirectory is sought.
-http_ssl As -http, but force lookup for ssl classes subdir.
Note that for HTTPS, single-port Java applet delivery
you can set X11VNC_HTTPS_DOWNLOAD_WAIT_TIME to the
max number of seconds to wait for the applet download
to finish. The default is 15.
-avahi Use the Avahi/mDNS ZeroConf protocol to advertise
this VNC server to the local network. (Related terms:
Rendezvous, Bonjour). Depending on your setup, you
may need to start avahi-daemon and open udp port 5353
in your firewall.
You can set X11VNC_AVAHI_NAME, X11VNC_AVAHI_HOST,
and/or X11VNC_AVAHI_PORT environment variables
to override the default values. For example:
-env X11VNC_AVAHI_NAME=wally
If the avahi API cannot be found at build time, a helper
program like avahi-publish(1) or dns-sd(1) will be tried
-mdns Same as -avahi.
-zeroconf Same as -avahi.
-connect string For use with "vncviewer -listen" reverse connections.
If "string" has the form "host" or "host:port"
the connection is made once at startup.
Use commas for a list of host's and host:port's.
E.g. -connect host1,host2 or host1:0,host2:5678.
Note that to reverse connect to multiple hosts at the
same time you will likely need to also supply: -shared
Note that unlike most vnc servers, x11vnc will require a
password for reverse as well as for forward connections.
(provided password auth has been enabled, -rfbauth, etc)
If you do not want to require a password for reverse
connections set X11VNC_REVERSE_CONNECTION_NO_AUTH=1 in
your environment before starting x11vnc.
If "string" contains "/" it is instead interpreted
as a file to periodically check for new hosts.
The first line is read and then the file is truncated.
Be careful about the location of this file if x11vnc
is running as root (e.g. via gdm(1), etc).
Repeater mode: Some services provide an intermediate
"vnc repeater": http://www.uvnc.com/addons/repeater.html
(and also http://koti.mbnet.fi/jtko/ for linux port)
that acts as a proxy/gateway. Modes like these require
an initial string to be sent for the reverse connection
before the VNC protocol is started. Here are the ways
to do this:
-connect pre=some_string+host:port
-connect pre128=some_string+host:port
-connect repeater=ID:1234+host:port
-connect repeater=23.45.67.89::5501+host:port
SSVNC notation is also supported:
-connect repeater://host:port+ID:1234
As with normal -connect usage, if the repeater port is
not supplied 5500 is assumed.
The basic idea is between the special tag, e.g. "pre="
and "+" is the pre-string to be sent. Note that in
this case host:port is the repeater server, NOT the
vnc viewer. Somehow the pre-string tells the repeater
server how to find the vnc viewer and connect you to it.
In the case pre=some_string+host:port, "some_string"
is simply sent. In the case preNNN=some_string+host:port
"some_string" is sent in a null padded buffer of
length NNN. repeater= is the same as pre250=, this is
the ultravnc repeater buffer size.
Strings like "\n" and "\r", etc. are expanded to
newline and carriage return. "\c" is expanded to
"," since the connect string is comma separated.
See also the -proxy option below for additional ways
to plumb reverse connections.
Reverse SSL: using -connect in -ssl mode makes x11vnc
act as an SSL client (initiates SSL connection) rather
than an SSL server. The idea is x11vnc might be
connecting to stunnel on the viewer side with the
viewer in listening mode. If you do not want this
behavior, use -env X11VNC_DISABLE_SSL_CLIENT_MODE=1.
With this the viewer side can act as the SSL client
as it normally does for forward connections.
Reverse SSL Repeater mode: This will work, but note
that if the VNC Client does any sort of a 'Fetch Cert'
action before connecting, then the Repeater will
likely drop the connection and both sides will need
to restart. Consider the use of -connect_or_exit
and -loop300,2 to have x11vnc reconnect once to the
repeater after the fetch. You will probably also want
to supply -sslonly to avoid x11vnc thinking the delay
in response means the connection is VeNCrypt. The env
var X11VNC_DISABLE_SSL_CLIENT_MODE=1 discussed above
may also be useful (i.e. the viewer can do a forward
connection as it normally does.)
IPv6: as of x11vnc 0.9.10 the -connect option should
connect to IPv6 hosts properly. If there are problems
you can disable IPv6 by setting -DX11VNC_IPV6=0
in CPPFLAGS when configuring. If there problems
connecting to IPv6 hosts consider a relay like the
included inet6to4 script or the -proxy option.
-connect_or_exit str As with -connect, except if none of the reverse
connections succeed, then x11vnc shuts down immediately
An easier to type alias for this option is '-coe'
By the way, if you do not want x11vnc to listen on
ANY interface use -rfbport 0 which is handy for the
-connect_or_exit mode.
-proxy string Use proxy in string (e.g. host:port) as a proxy for
making reverse connections (-connect or -connect_or_exit
options).
Web proxies are supported, but note by default most of
them only support destination connections to ports 443
or 563, so this might not be very useful (the viewer
would need to listen on that port or the router would
have to do a port redirection).
A web proxy may be specified by either "host:port"
or "http://host:port" (the port is required even if
it is the common choices 80 or 8080)
SOCKS4, SOCKS4a, and SOCKS5 are also supported.
SOCKS proxies normally do not have restrictions on the
destination port number.
Use a format like this: socks://host:port or
socks5://host:port. Note that ssh -D does not support
SOCKS4a, so use socks5://. For socks:// SOCKS4 is used
on a numerical IP and "localhost", otherwise SOCKS4a
is used (and so the proxy tries to do the DNS lookup).
An experimental mode is "-proxy http://host:port/..."
Note the "/" after the port that distinguishes it from
a normal web proxy. The port must be supplied even if
it is the default 80. For this mode a GET is done to
the supplied URL with the string host=H&port=P appended.
H and P will be the -connect reverse connect host
and port. Use the string "__END__" to disable the
appending. The basic idea here is that maybe some cgi
script provides the actual viewer hookup and tunnelling.
How to actually achieve this within cgi, php, etc. is
not clear... A custom web server or apache module
would be straight-forward.
Another experimental mode is "-proxy ssh://user@host"
in which case a SSH tunnel is used for the proxying.
"user@" is not needed unless your unix username is
different on "host". For a non-standard SSH port
use ssh://user@host:port. If proxies are chained (see
next paragraph) then the ssh one must be the first one.
If ssh-agent is not active, then the ssh password needs
to be entered in the terminal where x11vnc is running.
Examples:
-connect localhost:0 -proxy ssh://me@friends-pc:2222
-connect snoopy:0 -proxy ssh://ssh.company.com
Multiple proxies may be chained together in case one
needs to ricochet off of a number of hosts to finally
reach the VNC viewer. Up to 3 may be chained, separate
them by commas in the order they are to be connected to.
E.g.: http://host1:port1,socks5://host2:port2 or three
like: first,second,third
IPv6: as of x11vnc 0.9.10 the -proxy option should
connect to IPv6 hosts properly. If there are problems
you can disable IPv6 by setting -DX11VNC_IPV6=0
in CPPFLAGS when configuring. If there problems
connecting to IPv6 hosts consider a relay like the
included inet6to4 script.
-vncconnect Monitor the VNC_CONNECT X property set by the standard
-novncconnect VNC program vncconnect(1). When the property is
set to "host" or "host:port" establish a reverse
connection. Using xprop(1) instead of vncconnect may
work (see the FAQ). The -remote control mechanism uses
X11VNC_REMOTE channel, and this option disables/enables
it as well. Default: -vncconnect
To use different names for these X11 properties (e.g. to
have separate communication channels for multiple
x11vnc's on the same display) set the VNC_CONNECT or
X11VNC_REMOTE env. vars. to the string you want, for
example: -env X11VNC_REMOTE=X11VNC_REMOTE_12345
Both sides of the channel must use the same unique name.
The same can be done for the internal X11VNC_TICKER
property (heartbeat and timestamp) if desired.
-allow host1[,host2..] Only allow client connections from hosts matching
the comma separated list of hostnames or IP addresses.
Can also be a numerical IP prefix, e.g. "192.168.100."
to match a simple subnet, for more control build
LibVNCServer with libwrap support (See the FAQ). If the
list contains a "/" it instead is a interpreted
as a file containing addresses or prefixes that is
re-read each time a new client connects. Lines can be
commented out with the "#" character in the usual way.
-allow applies in -ssl mode, but not in -stunnel mode.
IPv6: as of x11vnc 0.9.10 a host can be specified
in IPv6 numerical format, e.g. 2001:4860:b009::93.
-localhost Basically the same as "-allow 127.0.0.1".
Note: if you want to restrict which network interface
x11vnc listens on, see the -listen option below.
E.g. "-listen localhost" or "-listen 192.168.3.21".
As a special case, the option "-localhost" implies
"-listen localhost".
A rare case, but for non-localhost -listen usage, if
you use the remote control mechanism (-R) to change
the -listen interface you may need to manually adjust
the -allow list (and vice versa) to avoid situations
where no connections (or too many) are allowed.
If you do not want x11vnc to listen on ANY interface
(evidently you are using -connect or -connect_or_exit,
or plan to use remote control: -R connect:host), use
-rfbport 0
IPv6: if IPv6 is supported, this option automatically
implies the IPv6 loopback address '::1' as well.
-unixsock str Listen on the unix socket (AF_UNIX) 'str'
for connections. This mode is for either local
connections or a tunnel endpoint where one wants the
file permission of the unix socket file to determine
what can connect to it. (This currently requires an
edit to libvnserver/rfbserver.c: comment out lines 310
and 311, 'close(sock)' and 'return NULL' in rfbserver.c
after the setsockopt() call.) Note that to disable all
tcp listening ports specify '-rfbport 0' and should be
useful with this mode. Example:
mkdir ~/s; chmod 700 ~/s;
x11vnc -unixsock ~/s/mysock -rfbport 0 ...
The SSVNC unix vncviewer can connect to unix sockets.
-listen6 str When in IPv6 listen mode "-6", listen only on the
network interface with address "str". It also works
for link scope addresses (fe80::219:dbff:fee5:3f92%eth0)
and IPv6 hostname strings (e.g. ipv6.google.com.)
Use LibVNCServer -listen option for the IPv4 interface.
-nolookup Do not use gethostbyname() or gethostbyaddr() to look up
host names or IP numbers. Use this if name resolution
is incorrectly set up and leads to long pauses as name
lookups time out, etc.
-input string Fine tuning of allowed user input. If "string" does
not contain a comma "," the tuning applies only to
normal clients. Otherwise the part before "," is
for normal clients and the part after for view-only
clients. "K" is for Keystroke input, "M" for
Mouse-motion input, "B" for Button-click input, "C"
is for Clipboard input, and "F" is for File transfer
(ultravnc only). Their presence in the string enables
that type of input. E.g. "-input M" means normal
users can only move the mouse and "-input KMBCF,M"
lets normal users do anything and enables view-only
users to move the mouse. This option is ignored when
a global -viewonly is in effect (all input is discarded
in that case).
-grabkbd When VNC viewers are connected, attempt to the grab
the keyboard so a (non-malicious) user sitting at the
physical display is not able to enter keystrokes.
This method uses XGrabKeyboard(3X11) and so it is
not secure and does not rule out the person at the
physical display injecting keystrokes by flooding the
server with them, grabbing the keyboard himself, etc.
Some degree of cooperation from the person at the
display is assumed. This is intended for remote
help-desk or educational usage modes.
Note: on some recent (12/2010) X servers and/or
desktops, -grabkbd no longer works: it prevents the
window manager from resizing windows and similar things.
Try -ungrabboth below (might not work.)
-grabptr As -grabkbd, but for the mouse pointer using
XGrabPointer(3X11). Unfortunately due to the way the X
server works, the mouse can still be moved around by the
user at the physical display, but he will not be able to
change window focus with it. Also some window managers
that call XGrabServer(3X11) for resizes, etc, will
act on the local user's input. Again, some degree of
cooperation from the person at the display is assumed.
-ungrabboth Whenever there is any input (either keyboard or
pointer), ungrab *both* the keyboard and the pointer
while injecting the synthetic input. This is to allow
window managers, etc. a chance to grab.
-grabalways Apply both -grabkbd and -grabptr even when no VNC
viewers are connected. If you only want one of them,
use the -R remote control to turn the other back on,
e.g. -R nograbptr.
-viewpasswd string Supply a 2nd password for view-only logins. The -passwd
(full-access) password must also be supplied.
-passwdfile filename Specify the LibVNCServer password via the first line
of the file "filename" (instead of via -passwd on
the command line where others might see it via ps(1)).
See the descriptions below for how to supply multiple
passwords, view-only passwords, to specify external
programs for the authentication, and other features.
If the filename is prefixed with "rm:" it will be
removed after being read. Perhaps this is useful in
limiting the readability of the file. In general, the
password file should not be readable by untrusted users
(BTW: neither should the VNC -rfbauth file: it is NOT
encrypted, only obscured with a fixed key).
If the filename is prefixed with "read:" it will
periodically be checked for changes and reread. It is
guaranteed to be reread just when a new client connects
so that the latest passwords will be used.
If "filename" is prefixed with "cmd:" then the
string after the ":" is run as an external command:
the output of the command will be interpreted as if it
were read from a password file (see below). If the
command does not exit with 0, then x11vnc terminates
immediately. To specify more than 1000 passwords this
way set X11VNC_MAX_PASSWDS before starting x11vnc.
The environment variables are set as in -accept.
Note that due to the VNC protocol only the first 8
characters of a password are used (DES key).
If "filename" is prefixed with "custom:" then a
custom password checker is supplied as an external
command following the ":". The command will be run
when a client authenticates. If the command exits with
0 the client is accepted, otherwise it is rejected.
The environment variables are set as in -accept.
The standard input to the custom command will be a
decimal digit "len" followed by a newline. "len"
specifies the challenge size and is usually 16 (the
VNC spec). Then follows len bytes which is the random
challenge string that was sent to the client. This is
then followed by len more bytes holding the client's
response (i.e. the challenge string encrypted via DES
with the user password in the standard situation).
The "custom:" scheme can be useful to implement
dynamic passwords or to implement methods where longer
passwords and/or different encryption algorithms
are used. The latter will require customizing the VNC
client as well. One could create an MD5SUM based scheme
for example.
File format for -passwdfile:
If multiple non-blank lines exist in the file they are
all taken as valid passwords. Blank lines are ignored.
Password lines may be "commented out" (ignored) if
they begin with the character "#" or the line contains
the string "__SKIP__". Lines may be annotated by use
of the "__COMM__" string: from it to the end of the
line is ignored. An empty password may be specified
via the "__EMPTY__" string on a line by itself (note
your viewer might not accept empty passwords).
If the string "__BEGIN_VIEWONLY__" appears on a
line by itself, the remaining passwords are used for
viewonly access. For compatibility, as a special case
if the file contains only two password lines the 2nd
one is automatically taken as the viewonly password.
Otherwise the "__BEGIN_VIEWONLY__" token must be
used to have viewonly passwords. (tip: make the 3rd
and last line be "__BEGIN_VIEWONLY__" to have 2
full-access passwords)
-showrfbauth filename Print to the screen the obscured VNC password kept in
the rfbauth file "filename" and then exit.
-unixpw [list] Use Unix username and password authentication. x11vnc
will use the su(1) program to verify the user's
password. [list] is an optional comma separated list
of allowed Unix usernames. If the [list] string begins
with the character "!" then the entire list is taken
as an exclude list. See below for per-user options
that can be applied.
A familiar "login:" and "Password:" dialog is
presented to the user on a black screen inside the
vncviewer. The connection is dropped if the user fails
to supply the correct password in 3 tries or does not
send one before a 45 second timeout. Existing clients
are view-only during this period.
If the first character received is "Escape" then the
unix username will not be displayed after "login:"
as it is typed. This could be of use for VNC viewers
that automatically type the username and password.
Since the detailed behavior of su(1) can vary from
OS to OS and for local configurations, test the mode
before deployment to make sure it is working properly.
x11vnc will attempt to be conservative and reject a
login if anything abnormal occurs.
One case to note: FreeBSD and the other BSD's by
default it is impossible for the user running x11vnc to
validate his *own* password via su(1) (commenting out
the pam_self.so entry in /etc/pam.d/su eliminates this
behavior). So the x11vnc login will always *FAIL* for
this case (even when the correct password is supplied).
A possible workaround for this on *BSD would be to
start x11vnc as root with the "-users +nobody" option
to immediately switch to user nobody where the su'ing
will proceed normally.
Another source of potential problems are PAM modules
that prompt for extra info, e.g. password aging modules.
These logins will fail as well even when the correct
password is supplied.
**IMPORTANT**: to prevent the Unix password being sent
in *clear text* over the network, one of two schemes
will be enforced: 1) the -ssl builtin SSL mode, or 2)
require both -localhost and -stunnel be enabled.
Method 1) ensures the traffic is encrypted between
viewer and server. A PEM file will be required, see the
discussion under -ssl below (under some circumstances
a temporary one can be automatically generated).
Method 2) requires the viewer connection to appear
to come from the same machine x11vnc is running on
(e.g. from a ssh -L port redirection). And that the
-stunnel SSL mode be used for encryption over the
network. (see the description of -stunnel below).
Note: as a convenience, if you ssh(1) in and start
x11vnc it will check if the environment variable
SSH_CONNECTION is set and appears reasonable. If it
does, then the -ssl or -stunnel requirement will be
dropped since it is assumed you are using ssh for the
encrypted tunnelling. -localhost is still enforced.
Use -ssl or -stunnel to force SSL usage even if
SSH_CONNECTION is set.
To override the above restrictions you can set
environment variables before starting x11vnc:
Set UNIXPW_DISABLE_SSL=1 to disable requiring either
-ssl or -stunnel (as under SSH_CONNECTION.) Evidently
you will be using a different method to encrypt the
data between the vncviewer and x11vnc: perhaps ssh(1)
or an IPSEC VPN. -localhost is still enforced (however,
see the next paragraph.)
Set UNIXPW_DISABLE_LOCALHOST=1 to disable the -localhost
requirement in -unixpw modes. One should never do this
(i.e. allow the Unix passwords to be sniffed on the
network.) This also disables the localhost requirement
for reverse connections (see below.)
Note that use of -localhost with ssh(1) (and no -unixpw)
is roughly the same as requiring a Unix user login
(since a Unix password or the user's public key
authentication is used by sshd on the machine where
x11vnc runs and only local connections from that machine
are accepted).
Regarding reverse connections (e.g. -R connect:host
and -connect host), when the -localhost constraint is
in effect then reverse connections can only be used
to connect to the same machine x11vnc is running on
(default port 5500). Please use a ssh or stunnel port
redirection to the viewer machine to tunnel the reverse
connection over an encrypted channel.
In -inetd mode the Method 1) will be enforced (not
Method 2). With -ssl in effect reverse connections
are disabled. If you override this via env. var, be
sure to also use encryption from the viewer to inetd.
Tip: you can also have your own stunnel spawn x11vnc
in -inetd mode (thereby bypassing inetd). See the FAQ
for details.
The user names in the comma separated [list] may have
per-user options after a ":", e.g. "fred:opts"
where "opts" is a "+" separated list of
"viewonly", "fullaccess", "input=XXXX", or
"deny", e.g. "karl,wally:viewonly,boss:input=M".
For "input=" it is the K,M,B,C described under -input.
If an item in the list is "*" that means those
options apply to all users. It ALSO implies all users
are allowed to log in after supplying a valid password.
Use "deny" to explicitly deny some users if you use
"*" to set a global option. If [list] begins with the
"!" character then "*" is ignored for checking if
the user is allowed, but the option values associated
with it do apply as normal.
There are also some utilities for checking passwords
if [list] starts with the "%" character. See the
quick_pw() function for more details. Description:
"%-" or "%stdin" means read one line from stdin.
"%env" means it is in $UNIXPW env var. A leading
"%/" or "%." means read the first line from the
filename that follows after the % character. % by
itself means prompt for the username and password.
Otherwise: %user:pass E.g. -unixpw %fred:swordfish
For the other cases user:pass is read from the indicated
source. If the password is correct 'Y user' is printed
and the program exit code is 0. If the password is
incorrect it prints 'N user' and the exit code is 1.
If there is some other error the exit code is 2.
This feature enables x11vnc to be a general unix user
password checking tool; it could be used from scripts
or other programs. These % password checks also apply
to the -unixpw_nis and -unixpw_cmd options.
For the % password check, if the env. var. UNIXPW_CMD
is set to a command then it is run as the user (assuming
the password is correct.) The output of the command is
not printed, the program or script must manage that by
some other means. The exit code of x11vnc will depend
on the exit code of the command that is run.
Use -nounixpw to disable unixpw mode if it was enabled
earlier in the cmd line (e.g. -svc mode)
-unixpw_nis [list] As -unixpw above, however do not use su(1) but rather
use the traditional getpwnam(3) + crypt(3) method to
verify passwords. All of the above -unixpw options and
constraints apply.
This mode requires that the encrypted passwords be
readable. Encrypted passwords stored in /etc/shadow
will be inaccessible unless x11vnc is run as root.
This is called "NIS" mode simply because in most
NIS setups user encrypted passwords are accessible
(e.g. "ypcat passwd") by an ordinary user and so that
user can authenticate ANY user.
NIS is not required for this mode to work (only that
getpwnam(3) return the encrypted password is required),
but it is unlikely it will work (as an ordinary user)
for most modern environments unless NIS is available.
On the other hand, when x11vnc is run as root it will
be able to to access /etc/shadow even if NIS is not
available (note running as root is often done when
running x11vnc from inetd and xdm/gdm/kdm).
Looked at another way, if you do not want to use the
su(1) method provided by -unixpw (i.e. su_verify()), you
can run x11vnc as root and use -unixpw_nis. Any users
with passwords in /etc/shadow can then be authenticated.
In -unixpw_nis mode, under no circumstances is x11vnc's
user password verifying function based on su called
(i.e. the function su_verify() that runs /bin/su
in a pseudoterminal to verify passwords.) However,
if -unixpw_nis is used in conjunction with the -find
and -create -display WAIT:... modes then, if x11vnc is
running as root, /bin/su may be called externally to
run the find or create commands.
-unixpw_cmd cmd As -unixpw above, however do not use su(1) but rather
run the externally supplied command "cmd". The first
line of its stdin will be the username and the second
line the received password. If the command exits
with status 0 (success) the VNC user will be accepted.
It will be rejected for any other return status.
Dynamic passwords and non-unix passwords, e.g. LDAP,
can be implemented this way by providing your own custom
helper program. Note that the remote viewer is given 3
tries to enter the correct password, and so the program
may be called in a row that many (or more) times.
If a list of allowed users is needed to limit who can
log in, use -unixpw [list] in addition to this option.
In FINDDISPLAY and FINDCREATEDISPLAY modes the "cmd"
will also be run with the RFB_UNIXPW_CMD_RUN env. var.
non-empty and set to the corresponding display
find/create command. The first two lines of input are
the username and passwd as in the normal case described
above. To support FINDDISPLAY and FINDCREATEDISPLAY,
"cmd" should run the requested command as the user
(and most likely refusing to run it if the password is
not correct.) Here is an example script (note it has
a hardwired bogus password "abc"!)
#!/bin/sh
# Example x11vnc -unixpw_cmd script.
# Read the first two lines of stdin (user and passwd)
read user
read pass
debug=0
if [ $debug = 1 ]; then
echo "user: $user" 1>&2
echo "pass: $pass" 1>&2
env | egrep -i 'rfb|vnc' 1>&2
fi
# Check if the password is valid.
# (A real example would use ldap lookup, etc!)
if [ "X$pass" != "Xabc" ]; then
exit 1 # incorrect password
fi
if [ "X$RFB_UNIXPW_CMD_RUN" = "X" ]; then
exit 0 # correct password
else
# Run the requested command (finddisplay)
if [ $debug = 1 ]; then
echo "run: $RFB_UNIXPW_CMD_RUN" 1>&2
fi
exec /bin/su - "$user" -c "$RFB_UNIXPW_CMD_RUN"
fi
In -unixpw_cmd mode, under no circumstances is x11vnc's
user password verifying function based on su called
(i.e. the function su_verify() that runs /bin/su in a
pseudoterminal to verify passwords.) It is up to the
supplied unixpw_cmd to do user switching if desired
and if it has the permissions to do so.
-find Find the user's display using FINDDISPLAY. This
is an alias for "-display WAIT:cmd=FINDDISPLAY".
Note: if a -display occurs later on the command line
it will override the -find setting.
For this and the next few options see -display WAIT:...
below for all of the details.
-finddpy Run the FINDDISPLAY program, print out the found
display (if any) and exit. Output is like: DISPLAY=:0.0
DISPLAY=:0.0,XPID=12345 or DISPLAY=:0.0,VT=7. XPID is
the process ID of the found X server. VT is the Linux
virtual terminal of the X server.
-listdpy Have the FINDDISPLAY program list all of your displays
(i.e. all the X displays on the local machine that you
have access rights to). x11vnc then exits.
-findauth [disp] Apply the -find/-finddpy heuristics to try to guess
the XAUTHORITY file for DISPLAY 'disp'. If 'disp'
is not supplied, then the value in the -display on
the cmdline is used; failing that $DISPLAY is used;
and failing that ":0" is used. x11vnc then exits.
If nothing is printed out, that means no XAUTHORITY was
found for 'disp'; i.e. failure. If "XAUTHORITY="
is printed out, that means use the default (i.e. do
not set XAUTHORITY). If "XAUTHORITY=/path/to/file"
is printed out, then use that file.
XDM/GDM/KDM: if you are running x11vnc as root and want
to find the XAUTHORITY before anyone has logged into an
X session yet, use: x11vnc -env FD_XDM=1 -findauth ...
(This will also find the XAUTHORITY if a user is already
logged into the X session.) When running as root,
FD_XDM=1 will be tried if the initial -findauth fails.
-create First try to find the user's display using FINDDISPLAY,
if that doesn't succeed create an X session via the
FINDCREATEDISPLAY method. This is an alias for
"-display WAIT:cmd=FINDCREATEDISPLAY-Xvfb".
Note: if a -display occurs later on the command line
it will override the -create setting.
SSH NOTE: for both -find and -create you can (should!)
add the "-localhost" option to force SSH tunnel access.
-xdummy As in -create, except Xdummy instead of Xvfb.
-xvnc As in -create, except Xvnc instead of Xvfb.
-xvnc_redirect As in -create, except Xvnc.redirect instead of Xvfb.
-xdummy_xvfb Sets WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb
-create_xsrv str Sets WAIT:cmd=FINDCREATEDISPLAY-<str> Can be on cmdline
after anything that sets WAIT:.. and other things
(e.g. -svc, -xdmsvc) to adjust the X server list.
Example: -svc ... -create_xsrv Xdummy,X
-svc Terminal services mode based on SSL access. Alias for
-display WAIT:cmd=FINDCREATEDISPLAY-Xvfb -unixpw -users
unixpw= -ssl SAVE Also "-service".
Note: if a -display, -unixpw, -users, or -ssl occurs
later on the command line it will override the -svc
setting.
-svc_xdummy As -svc except Xdummy instead of Xvfb.
-svc_xvnc As -svc except Xvnc instead of Xvfb.
-svc_xdummy_xvfb As -svc with Xdummy,Xvfb.
-xdmsvc Display manager Terminal services mode based on SSL.
Alias for -display WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp
-unixpw -users unixpw= -ssl SAVE Also "-xdm_service".
Note: if a -display, -unixpw, -users, or -ssl occurs
later on the command line it will override the -xdmsvc
setting.
To create a session a user will have to first log in
to the -unixpw dialog and then log in again to the
XDM/GDM/KDM prompt. Subsequent re-connections will
only require the -unixpw password. See the discussion
under -display WAIT:... for more details about XDM,
etc configuration.
Remember to enable XDMCP in the xdm-config, gdm.conf,
or kdmrc configuration file. See -display WAIT: for
more info.
-sshxdmsvc Display manager Terminal services mode based on SSH.
Alias for -display WAIT:cmd=FINDCREATEDISPLAY-Xvfb.xdmcp
-localhost.
The -localhost option constrains connections to come
in via a SSH tunnel (which will require a login).
To create a session a user will also have to log into
the XDM GDM KDM prompt. Subsequent re-connections will
only only require the SSH login. See the discussion
under -display WAIT:... for more details about XDM,
etc configuration.
Remember to enable XDMCP in the xdm-config, gdm.conf,
or kdmrc configuration file. See -display WAIT: for
more info.
-unixpw_system_greeter Present a "Press 'Escape' for System Greeter" option
to the connecting VNC client in combined -unixpw
and xdmcp FINDCREATEDISPLAY modes (e.g. -xdmsvc).
Normally in a -unixpw mode the VNC client must
supply a valid username and password to gain access.
However, if -unixpw_system_greeter is supplied AND
the FINDCREATEDISPLAY command matches 'xdmcp', then
the user has the option to press Escape and then get a
XDM/GDM/KDM login/greeter panel instead. They will then
supply a username and password directly to the greeter.
Otherwise, in xdmcp FINDCREATEDISPLAY mode the user
must supply his username and password TWICE. First to
the initial unixpw login dialog, and second to the
subsequent XDM/GDM/KDM greeter. Note that if the user
re-connects and supplies his username and password in
the unixpw dialog the xdmcp greeter is skipped and
he is connected directly to his existing X session.
So the -unixpw_system_greeter option avoids the extra
password at X session creation time.
Example: x11vnc -xdmsvc -unixpw_system_greeter
See -unixpw and -display WAIT:... for more info.
The special options after a colon at the end of the
username (e.g. user:solid) described under -display
WAIT: are also applied in this mode if they are typed
in before the user hits Escape. The username is ignored
but the colon options are not.
The default message is 2 lines in a small font, set
the env. var. X11VNC_SYSTEM_GREETER1=true for a 1 line
message in a larger font.
If the user pressed Escape the FINDCREATEDISPLAY command
will be run with the env. var. X11VNC_XDM_ONLY=1.
Remember to enable XDMCP in the xdm-config, gdm.conf,
or kdmrc configuration file. See -display WAIT: for
more info.
-redirect port As in FINDCREATEDISPLAY-Xvnc.redirect mode except
redirect immediately (i.e. without X session finding
or creation) to a VNC server listening on port. You
can also supply host:port to redirect to a different
machine.
If 0 <= port < 200 it is taken as a VNC display (5900 is
added to get the actual port), if port < 0 then -port
is used.
Probably the only reason to use the -redirect option
is in conjunction with SSL support, e.g. -ssl SAVE.
This provides an easy way to add SSL encryption to a VNC
server that does not support SSL (e.g. Xvnc or vnc.so)
In fact, the protocol does not even need to be VNC,
and so "-rfbport port1 -ssl SAVE -redirect host:port2"
can act as a replacement for stunnel(1).
This mode only allows one redirected connection.
The -forever option does not apply. Use -inetd or
-loop for persistent service.
-display WAIT:... A special usage mode for the normal -display option.
Useful with -unixpw, but can be used independently
of it. If the display string begins with WAIT: then
x11vnc waits until a VNC client connects before opening
the X display (or -rawfb device).
This could be useful for delaying opening the display
for certain usage modes (say if x11vnc is started at
boot time and no X server is running or users logged
in yet).
If the string is, e.g. WAIT:0.0 or WAIT:1, i.e. "WAIT"
in front of a normal X display, then that indicated
display is used.
One can also insert a geometry between colons, e.g.
WAIT:1280x1024:... to set the size of the display the
VNC client first attaches to since some VNC viewers
will not automatically adjust to a new framebuffer size.
A more interesting case is like this:
WAIT:cmd=/usr/local/bin/find_display
in which case the command after "cmd=" is run to
dynamically work out the DISPLAY and optionally the
XAUTHORITY data. The first line of the command output
must be of the form DISPLAY=<xdisplay>. On Linux
if the virtual terminal is known append ",VT=n" to
this string and the chvt(1) program will also be run.
Any remaining output is taken as XAUTHORITY data.
It can be either of the form XAUTHORITY=<file> or raw
xauthority data for the display. For example;
xauth extract - $DISPLAY"
NOTE: As specified in the previous paragraph, you can
supply your own WAIT:cmd=... program or script, BUT
there are two very useful *BUILT-IN* ones: FINDDISPLAY
(alias -find above) and FINDCREATEDISPLAY (alias -create
above.) Most people use these instead of creating
their own script. Read the following (especially the
BUILT-IN modes sections) to see how to configure these
two useful builtin -display WAIT: modes.
In the case of -unixpw (and -unixpw_nis only if x11vnc
is running as root), then the cmd= command is run
as the user who just authenticated via the login and
password prompt.
In the case of -unixpw_cmd, the commands will also be
run as the logged-in user, as long as the user-supplied
helper program supports RFB_UNIXPW_CMD_RUN (see the
-unixpw_cmd option.)
Also in the case of -unixpw, the user logging in can
place a colon at the end of her username and supply
a few options: scale=, scale_cursor= (or sc=), solid
(or so), id=, clear_mods (or cm), clear_keys (or
ck), clear_all (or ca), repeat, speeds= (or sp=),
readtimeout= (or rd=), viewonly (or vo), nodisplay=
(or nd=), rotate= (or ro=), or noncache (or nc),
all separated by commas if there is more than one.
After the user logs in successfully, these options will
be applied to the VNC screen. For example,
login: fred:scale=3/4,sc=1,repeat
Password: ...
login: runge:sp=modem,rd=120,solid
for convenience m/n implies scale= e.g. fred:3/4 If you
type and enter your password incorrectly, to retrieve
your long "login:" line press the Up arrow once
(before typing anything else).
Most of these colon options only apply to the builtin
FINDDISPLAY and FINDCREATEDISPLAY modes, but note
that they are passed to the extrenal command in the
environment as well and so could be used.
In the login panel, press F1 to get a list of the
available options that you can add after the username.
Another option is "geom=WxH" or "geom=WxHxD" (or
ge=). This only has an effect in FINDCREATEDISPLAY
mode when a virtual X server such as Xvfb is going
to be created. It sets the width and height of
the new display, and optionally the color depth as
well.
You can also supply "gnome", "kde", "twm",
"fvwm", "mwm", "dtwm", "wmaker", "xfce",
"lxde", "enlightenment", "Xsession", or
"failsafe" (same as "xterm") to have the created
display use that mode for the user session.
Specify "tag=..." to set the unique FD_TAG desktop
session tag described below. Note: this option will
be ignored if the FD_TAG env. var. is already set or
if the viewer-side supplied value is not completely
composed of alphanumeric or '_' or '-' characters.
User preferences file: Instead of having the user type
in geom=WxH,... etc. every time he logs in to find
or create his X session, if you set FD_USERPREFS to
a string that does not contain the "/" character,
then the user's home directory is prepended to that
string and if the file exists its first line is read
and appended to any options he supplied at the login:
prompt. For example -env FD_USERPREFS=.x11vnc_create
and the user put "geom=1600x1200" in his
~/.x11vnc_create file.
To disable the option setting set the environment
variable X11VNC_NO_UNIXPW_OPTS=1 before starting x11vnc.
To set any other options, the user can use the gui
(x11vnc -gui connect) or the remote control method
(x11vnc -R opt:val) during his VNC session.
So we see the combination of -display WAIT:cmd=... and
-unixpw allows automatic pairing of an unix
authenticated VNC user with his desktop. This could
be very useful on SunRays and also any system where
multiple users share a given machine. The user does
not need to remember special ports or passwords set up
for his desktop and VNC.
A nice way to use WAIT:cmd=... is out of inetd(8)
(it automatically forks a new x11vnc for each user).
You can have the x11vnc inetd spawned process run as,
say, root or nobody. When run as root (for either inetd
or display manager), you can also supply the option
"-users unixpw=" to have the x11vnc process switch to
the user as well. Note: there will be a 2nd SSL helper
process that will not switch, but it is only encoding
and decoding the encrypted stream at that point.
BUILT-IN modes:
-- Automatic Finding of User X Sessions --
As a special case, WAIT:cmd=FINDDISPLAY will run a
script that works on most Unixes to determine a user's
DISPLAY variable and xauthority data (see who(1)).
NOTE: The option "-find" is an alias for this mode.
To have this default script printed to stdout (e.g. for
customization) run with WAIT:cmd=FINDDISPLAY-print To
have the script run to print what display it would find
use "-finddpy" or WAIT:cmd=FINDDISPLAY-run
The standard script runs xdpyinfo(1) run on potential
displays. If your X server(s) have a login greeter
that exclusively grabs the Xserver, then xdpyinfo
blocks forever and this mode will not work. See
www.karlrunge.com/x11vnc/faq.html#faq-display-manager
for how to disable this for dtgreet on Solaris and
possibly for other greeters.
In -find/cmd=FINDDISPLAY mode, if you set FD_XDM=1,
e.g. 'x11vnc -env FD_XDM=1 -find ...' and x11vnc is
running as root (e.g. inetd) then it will try to find
the XAUTHORITY file of a running XDM/GDM/KDM login
greeter (i.e. no user has logged into an X session yet.)
As another special case, WAIT:cmd=HTTPONCE will allow
x11vnc to service one http request and then exit.
This is usually done in -inetd mode to run on, say,
port 5800 and allow the Java vncviewer to be downloaded
by client web browsers. For example:
5815 stream tcp nowait root /usr/sbin/tcpd /.../x11vnc \
-inetd -q -http_ssl -prog /.../x11vnc \
-display WAIT:cmd=HTTPONCE
Where /.../x11vnc is the full path to x11vnc.
It is used in the Apache SSL-portal example (see FAQ).
In this mode you can set X11VNC_SKIP_DISPLAY to a
comma separated list of displays (e.g. ":0,:1") to
ignore in the finding process. The ":" is optional.
Ranges n-m e.g. 0-20 can also be supplied. This string
can also be set by the connecting user via "nd="
using "+" instead of "," If "nd=all" or you set
X11VNC_SKIP_DISPLAY=all then all display finding fails
as if you set X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 (below.)
On some systems lsof(1) can be very slow. Set the
env. var. FIND_DISPLAY_NO_LSOF=1 to skip using lsof to
try to find the Linux VT the X server is running on.
set FIND_DISPLAY_NO_VT_FIND=1 to avoid looking at all.
-- Automatic Creation of User X Sessions --
An interesting option is WAIT:cmd=FINDCREATEDISPLAY
that is like FINDDISPLAY in that is uses the same method
to find an existing display. However, if it does not
find one it will try to *start* up an X server session
for the user. This is the only time x11vnc tries to
actually start up an X server.
NOTE: The option "-create" is an alias for this mode.
It will start looking for an open display number at :20
Override via X11VNC_CREATE_STARTING_DISPLAY_NUMBER=n
By default 80 X displays are allowed (i.e. going to :99)
Override via X11VNC_CREATE_MAX_DISPLAYS=n
For its heuristics, the create display script sets
LC_ALL=C so that command output is uniform. By default
it will try to restore LC_ALL right before starting the
user session. However, if you don't mind it keeping
LC_ALL=C set the env. var.: X11VNC_CREATE_LC_ALL_C_OK=1
By default FINDCREATEDISPLAY will try Xvfb and then
Xdummy:
The Xdummy wrapper is part of the x11vnc source code
(x11vnc/misc/Xdummy) It should be available in PATH
and have run "Xdummy -install" once to create the
shared library. Xdummy only works on Linux. As of
12/2009 it no longer needs to be run as root, and the
default is to not run as root. In some circumstances
permissions may require running it as root, in these
cases specify FD_XDUMMY_RUN_AS_ROOT=1, this is the same
as supplying -root to the Xdummy cmdline.
Xvfb is available on most platforms and does not
require root.
An advantage of Xdummy over Xvfb is that Xdummy supports
RANDR dynamic screen resizing.
When x11vnc exits (i.e. user disconnects) the X
server session stays running in the background.
The FINDDISPLAY will find it directly next time.
The user must exit the X session in the usual way for
it to terminate (or kill the X server process if all
else fails).
To troubleshoot the FINDCREATEDISPLAY mechanism,
set the following env. var. to an output log file,
e.g -env CREATE_DISPLAY_OUTPUT=/tmp/mydebug.txt
So this is a somewhat odd mode for x11vnc in that it
will start up and poll virtual X servers! This can
be used from, say, inetd(8) to provide a means of
definitely getting a desktop (either real or virtual)
on the machine. E.g. a desktop service:
5900 stream tcp nowait root /usr/sbin/tcpd /.../x11vnc
-inetd -q -http -ssl SAVE -unixpw -users unixpw=\
-passwd secret -prog /.../x11vnc \
-display WAIT:cmd=FINDCREATEDISPLAY
Where /.../x11vnc is the full path to x11vnc.
See the -svc/-service option alias above.
If for some reason you do not want x11vnc to ever
try to find an existing display set the env. var
X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 (also -env ...)
This is the same as setting X11VNC_SKIP_DISPLAY=all or
supplying "nd=all" after "username:"
Use WAIT:cmd=FINDCREATEDISPLAY-print to print out the
script that is used for this.
You can specify the preferred X server order via e.g.,
WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb,X and/or leave
out ones you do not want. The the case "X" means try
to start up a real, hardware X server using xinit(1)
or startx(1). If there is already an X server running
the X case may only work on Linux (see startx(1)).
"Xvnc" will start up a VNC X server (real-
or tight-vnc, e.g. use if Xvfb is not available).
"Xsrv" will start up the server program in the
variable "FD_XSRV" if it is non-empty. You can make
this be a wrapper script if you like (it must handle :N,
-geometry, and -depth and other X server options).
You can set the environment variable FD_GEOM (or
X11VNC_CREATE_GEOM) to WxH or WxHxD to set the width
and height and optionally the color depth of the
created display. You can also set FD_SESS to be the
session (short name of the windowmanager: kde, gnome,
twm, failsafe, etc.). FD_OPTS contains extra options
to pass to the X server. You can also set FD_PROG to
be the full path to the session/windowmanager program.
More FD tricks: FD_CUPS=port or FD_CUPS=host:port
will set the cups printing environment. Similarly for
FD_ESD=port or FD_ESD=host:port for esddsp sound
redirection. Set FD_EXTRA to a command to be run a
few seconds after the X server starts up. Set FD_TAG
to be a unique name for the session, it is set as an
X property, that makes FINDDISPLAY only find sessions
with that tag value.
Set FD_XDMCP_IF to the network interface that the
display manager is running on; default is 'localhost'
but you may need to set it to '::1' on some IPv6 only
systems or misconfigured display managers.
If you want the FINDCREATEDISPLAY session to contact an
XDMCP login manager (xdm/gdm/kdm) on the same machine,
then use "Xvfb.xdmcp" instead of "Xvfb", etc.
The user will have to supply his username and password
one more time (but he gets to select his desktop type
so that can be useful). For this to work, you will
need to enable localhost XDMCP (udp port 177) for the
display manager. This seems to be:
for gdm in gdm.conf: Enable=true in section [xdmcp]
for kdm in kdmrc: Enable=true in section [Xdmcp]
for xdm in xdm-config: DisplayManager.requestPort: 177
See the shorthand options above "-svc", "-xdmsvc"
and "-sshxdmsvc" that specify the above options for
some useful cases.
If you set the env. var WAITBG=1 x11vnc will go into
the background once listening in wait mode.
Another special mode is FINDCREATEDISPLAY-Xvnc.redirect,
(or FINDDISPLAY-Xvnc.redirect). In this case it will
start up Xvnc as above if needed, but instead of
polling it in its normal way, it simply does a socket
redirection of the connected VNC viewer to the Xvnc.
So in Xvnc.redirect x11vnc does no VNC but merely
transfers the data back and forth. This should be
faster then x11vnc's polling method, but not as fast
as connecting directly to the Xvnc with the VNC Viewer.
The idea here is to take advantage of x11vnc's display
finding/creating scheme, SSL, and perhaps a few others.
Most of x11vnc's options do not apply in this mode.
Xvnc.redirect should also work for the vnc.so X server
module for the h/w display however it will work only
for finding the display and the user must already be
logged into the X console.
-vencrypt mode The VeNCrypt extension to the VNC protocol allows
encrypted SSL/TLS connections. If the -ssl mode is
enabled, then VeNCrypt is enabled as well BY DEFAULT
(they both use a SSL/TLS tunnel, only the protocol
handshake is a little different.)
To control when and how VeNCrypt is used, specify the
mode string. If mode is "never", then VeNCrypt is
not used. If mode is "support" (the default) then
VeNCrypt is supported. If mode is "only", then the
similar and older ANONTLS protocol is not simultaneously
supported. x11vnc's normal SSL mode (vncs://) will be
supported under -ssl unless you set mode to "force".
If mode is prefixed with "nodh:", then Diffie Hellman
anonymous key exchange is disabled. If mode is prefixed
with "nox509:", then X509 key exchange is disabled.
To disable all Anonymous Diffie-Hellman access
(susceptible to Man-In-The-Middle attack) you will need
to supply "-vencrypt nodh:support -anontls never"
or "-vencrypt nodh:only"
If mode is prefixed with "newdh:", then new Diffie
Hellman parameters are generated for each connection
(this can be time consuming: 1-60 secs; see -dhparams
below for a faster way) rather than using the
fixed values in the program. Using fixed, publicly
known values is not known to be a security problem.
This setting applies to ANONTLS as well.
Long example: -vencrypt newdh:nox509:support
Also, if mode is prefixed with "plain:", then
if -unixpw mode is active the VeNCrypt "*Plain"
username+passwd method is enabled for Unix logins.
Otherwise in -unixpw mode the normal login panel is
provided.
You *MUST* supply the -ssl option for VeNCrypt to
be active. The -vencrypt option only fine-tunes its
operation.
-anontls mode The ANONTLS extension to the VNC protocol allows
encrypted SSL/TLS connections. If the -ssl mode is
enabled, then ANONTLS is enabled as well BY DEFAULT
(they both use a SSL/TLS tunnel, only the protocol
handshake is a little different.)
ANONTLS is an older SSL/TLS mode introduced by vino.
It is referred to as 'TLS' for its registered VNC
security-type name, but we use the more descriptive
'ANONTLS' here because it provides only Anonymous
Diffie-Hellman encrypted connections, and hence no
possibility for certificate authentication.
To control when and how ANONTLS is used, specify the
mode string. If mode is "never", then ANONTLS is not
used. If mode is "support" (the default) then ANONTLS
is supported. If mode is "only", then the similar
VeNCrypt protocol is not simultaneously supported.
x11vnc's normal SSL mode (vncs://) will be supported
under -ssl unless you set mode to "force".
If mode is prefixed with "newdh:", then new Diffie
Hellman parameters are generated for each connection
(this can be time consuming: 1-60 secs; see -dhparams
below for a faster way) rather than using the
fixed values in the program. Using fixed, publicly
known values is not known to be a security problem.
This setting applies to VeNCrypt as well. See the
description of "plain:" under -vencrypt.
Long example: -anontls newdh:plain:support
You *MUST* supply the -ssl option for ANONTLS to
be active. The -anontls option only fine-tunes its
operation.
-sslonly Same as: "-vencrypt never -anontls never" i.e. it
disables the VeNCrypt and ANONTLS encryption methods
and only allows standard SSL tunneling. You must also
supply the -ssl ... option (see below.)
-dhparams file For some operations a set of Diffie Hellman parameters
(prime and generator) is needed. If so, use the
parameters in "file". In particular, the VeNCrypt and
ANONTLS anonymous DH mode need them. By default a
fixed set is used. If you do not want to do that you
can specify "newdh:" to the -vencrypt and -anontls
options to generate a new set each session. If that
is too slow for you, use -dhparams file to a set you
created manually via "openssl dhparam -out file 1024"
-nossl Disable the -ssl option (see below). Since -ssl is off
by default -nossl would only be used on the commandline
to unset any *earlier* -ssl option (or -svc...)
-ssl [pem] Use the openssl library (www.openssl.org) to provide a
built-in encrypted SSL/TLS tunnel between VNC viewers
and x11vnc. This requires libssl support to be
compiled into x11vnc at build time. If x11vnc is not
built with libssl support it will exit immediately when
-ssl is prescribed. See the -stunnel option below for
an alternative.
The VNC Viewer-side needs to support SSL/TLS as well.
See this URL and also the discussion below for
ideas on how to enable SSL support for the viewer:
http://www.karlrunge.com/x11vnc/faq.html#faq-ssl-tun
nel-viewers . x11vnc provides an SSL enabled Java
viewer applet in the classes/ssl directory (-http or
-httpdir options.) The SSVNC viewer package supports
SSL tunnels too.
If the VNC Viewer supports VeNCrypt or ANONTLS (vino's
encryption mode) they are also supported by the -ssl
mode (see the -vencrypt and -anontls options for more
info; use -sslonly to disable both of them.)
Use "-ssl /path/to/mycert.pem" to specify an SSL
certificate file in PEM format to use to identify and
provide a key for this server. See openssl(1) for more
info about PEMs and the -sslGenCert and "-ssl SAVE"
options below for how to create them.
The connecting VNC viewer SSL tunnel can (at its option)
authenticate this server if it has the public key part
of the certificate (or a common certificate authority,
CA, is a more sophisticated way to verify this server's
cert, see -sslGenCA below). This authentication is
done to prevent Man-In-The-Middle attacks. Otherwise,
if the VNC viewer simply accepts this server's key
WITHOUT verification, the traffic is protected from
passive sniffing on the network, but *NOT* from
Man-In-The-Middle attacks. There are hacker tools
like dsniff/webmitm and cain that implement SSL
Man-In-The-Middle attacks.
If [pem] is empty or the string "SAVE" then the
openssl(1) command must be available to generate the
certificate the first time. A self-signed certificate
is generated (see -sslGenCA and -sslGenCert for use
of a Certificate Authority.) It will be saved to the
file ~/.vnc/certs/server.pem. On subsequent calls if
that file already exists it will be used directly.
Use "SAVE_NOPROMPT" to avoid being prompted to
protect the generated key with a passphrase. However in
-inetd and -bg modes there will be no prompting for a
passphrase in either case.
If [pem] is "SAVE_PROMPT" the server.pem certificate
will be created based on your answers to its prompts for
all info such as OrganizationalName, CommonName, etc.
Use "SAVE-<string>" and "SAVE_PROMPT-<string>"
to refer to the file ~/.vnc/certs/server-<string>.pem
instead (it will be generated if it does not already
exist). E.g. "SAVE-charlie" will store to the file
~/.vnc/certs/server-charlie.pem
Examples: x11vnc -ssl SAVE -display :0 ...
x11vnc -ssl SAVE-someother -display :0 ...
If [pem] is "TMP" and the openssl(1) utility
command exists in PATH, then a temporary, self-signed
certificate will be generated for this session. If
openssl(1) cannot be used to generate a temporary
certificate x11vnc exits immediately. The temporary
cert will be discarded when x11vnc exits.
If successful in using openssl(1) to generate a
temporary certificate in "SAVE" or "TMP" creation
modes, the public part of it will be displayed to stderr
(e.g. one could copy it to the client-side to provide
authentication of the server to VNC viewers.)
NOTE: In "TMP" mode, unless you safely copy the
public part of the temporary Cert to the viewer for
authenticate *every time* (unlikely...), then only
passive sniffing attacks are prevented and you are
still open to Man-In-The-Middle attacks. This is
why the default "SAVE" mode is preferred (and more
sophisticated CA mode too). Only with saved keys AND
the VNC viewer authenticating them (via the public
certificate), are Man-In-The-Middle attacks prevented.
If [pem] is "ANON" then the Diffie-Hellman anonymous
key exchange method is used. In this mode there
are *no* SSL certificates and so it is not possible
to authenticate either the VNC server or VNC client.
Thus only passive network sniffing attacks are avoided:
the "ANON" method is susceptible to Man-In-The-Middle
attacks. "ANON" is not recommended; instead use
a SSL PEM you created or the default "SAVE" method.
See -ssldir below to use a directory besides the
default ~/.vnc/certs
If your x11vnc binary was not compiled with OpenSSL
library support, use of the -ssl option will induce an
immediate failure and exit. For such binaries, consider
using the -stunnel option for SSL encrypted connections.
Misc Info: In temporary cert creation mode "TMP", set
the env. var. X11VNC_SHOW_TMP_PEM=1 to have x11vnc print
out the entire certificate, including the PRIVATE KEY
part, to stderr. There are better ways to get/save this
info. See "SAVE" above and "-sslGenCert" below.
-ssltimeout n Set SSL read timeout to n seconds. In some situations
(i.e. an iconified viewer in Windows) the viewer stops
talking and the connection is dropped after the default
timeout (25s for about the first minute, 43200s later).
Set to zero to poll forever. Set to a negative value
to use the builtin setting.
Note that this value does NOT apply to the *initial* ssl
init connection. The default timeout for that is 20sec.
Use -env SSL_INIT_TIMEOUT=n to modify it.
-sslnofail Exit at the first SSL connection failure. Useful when
scripting SSL connections (e.g. x11vnc is started via
ssh) and you do not want x11vnc waiting around for more
connections, tying up ports, etc.
-ssldir dir Use "dir" as an alternate ssl certificate and key
management toplevel directory. The default is
~/.vnc/certs
This directory is used to store server and other
certificates and keys and also other materials. E.g. in
the simplest case, "-ssl SAVE" will store the x11vnc
server cert in dir/server.pem
Use of alternate directories via -ssldir allows you to
manage multiple VNC Certificate Authority (CA) keys.
Another use is if ~/.vnc/cert is on an NFS share you
might want your certificates and keys to be on a local
filesystem to prevent network snooping (for example
-ssldir /var/lib/x11vnc-certs).
-ssldir affects nearly all of the other -ssl* options,
e.g. -ssl SAVE, -sslGenCert, etc..
-sslverify path For either of the -ssl or -stunnel modes, use "path"
to provide certificates to authenticate incoming VNC
*Client* connections (normally only the server is
authenticated in SSL.) This can be used as a method
to replace standard password authentication of clients.
If "path" is a directory it contains the client (or CA)
certificates in separate files. If path is a file,
it contains one or more certificates. See special tokens
below. These correspond to the "CApath = dir" and
"CAfile = file" stunnel options. See the stunnel(8)
manpage for details.
Examples:
x11vnc -ssl -sslverify ~/my.crt
x11vnc -ssl -sslverify ~/my_pem_dir/
Note that if path is a directory, it must contain
the certs in separate files named like <HASH>.0, where
the value of <HASH> is found by running the command
"openssl x509 -hash -noout -in file.crt". Evidently
one uses <HASH>.1 if there is a collision...
The the key-management utility "-sslCertInfo HASHON"
and "-sslCertInfo HASHOFF" will create/delete these
hashes for you automatically (via symlink) in the HASH
subdirs it manages. Then you can point -sslverify to
the HASH subdir.
Special tokens: in -ssl mode, if "path" is not a file or
a directory, it is taken as a comma separated list of
tokens that are interpreted as follows:
If a token is "CA" that means load the CA/cacert.pem
file from the ssl directory. If a token is "clients"
then all the files clients/*.crt in the ssl directory
are loaded. Otherwise the file clients/token.crt
is attempted to be loaded. As a kludge, use a token
like ../server-foo to load a server cert if you find
that necessary.
Use -ssldir to use a directory different from the
~/.vnc/certs default.
Note that if the "CA" cert is loaded you do not need
to load any of the certs that have been signed by it.
You will need to load any additional self-signed certs
however.
Examples:
x11vnc -ssl -sslverify CA
x11vnc -ssl -sslverify self:fred,self:jim
x11vnc -ssl -sslverify CA,clients
Usually "-sslverify CA" is the most effective.
See the -sslGenCA and -sslGenCert options below for
how to set up and manage the CA framework.
NOTE: the following utilities, -sslGenCA, -sslGenCert,
-sslEncKey, -sslCertInfo, and -sslCRL are provided for
completeness, but for casual usage they are overkill.
They provide VNC Certificate Authority (CA) key creation
and server / client key generation and signing. So they
provide a basic Public Key management framework for
VNC-ing with x11vnc. (note that they require openssl(1)
be installed on the system)
However, the simplest usage mode, "-ssl TMP" (where
x11vnc automatically generates its own, self-signed,
temporary key and the VNC viewers always accept it,
e.g. accepting via a dialog box) is probably safe enough
for most scenarios. CA management is not needed.
To protect against Man-In-The-Middle attacks the "TMP"
mode can be improved by using "-ssl SAVE" (same as
"-ssl", i.e. the default) to have x11vnc create a
longer term self-signed certificate, and then (safely)
copy the corresponding public key cert to the desired
client machines (care must be taken the private key part
is not stolen; you will be prompted for a passphrase).
So keep in mind no CA key creation or management
(-sslGenCA and -sslGenCert) is needed for either of
the above two common usage modes.
One might want to use -sslGenCA and -sslGenCert
if you had a large number of VNC client and server
workstations. That way the administrator could generate
a single CA key with -sslGenCA and distribute its
certificate part to all of the workstations.
Next, he could create signed VNC server keys
(-sslGenCert server ...) for each workstation or user
that then x11vnc would use to authenticate itself to
any VNC client that has the CA cert.
Optionally, the admin could also make it so the
VNC clients themselves are authenticated to x11vnc
(-sslGenCert client ...) For this -sslverify would be
pointed to the CA cert (and/or self-signed certs).
x11vnc will be able to use all of these cert and
key files. On the VNC client side, they will need to
be "imported" somehow. Web browsers have "Manage
Certificates" actions as does the Java applet plugin
Control Panel. stunnel can also use these files (see
the ss_vncviewer example script in the FAQ and SSVNC.)
-sslCRL path Set the Certificate Revocation Lists (CRL) to "path".
This setting applies for both -ssl and -stunnel modes.
If path is a file, the file contains one or more CRLs
in PEM format. If path is a directory, it contains
hash named files of CRLs in the usual OpenSSL manner.
See the OpenSSL and stunnel(8) documentation for
more info.
This option only applies if -sslverify has been
supplied: it checks for revocation along the
certificate chain used to verify the VNC client.
The -sslCRL setting will be ignored when -sslverify is
not specified.
Note that if a CRL's expiration date has passed, all
SSL connections will fail regardless of if they are
related to the subject of the CRL or not.
Only rarely will one's x11vnc -ssl infrastructure be so
large that this option would be useful (since normally
maintaining the contents of the -sslverify file or
directory should be enough.) However, when using
x11vnc with a Certificate Authority (see -sslGenCA)
to authenticate Clients via SSL/TLS, the -sslCRL option
can be useful to revoke users' certs whose private SSL
keys were lost or stolen (e.g. laptop.) This way a new
CA cert+key does not need to be created and new signed
client keys generated and distributed to all users.
To create a CRL file with revoked certificates the
commands 'openssl ca -revoke ...' and 'openssl ca
-gencrl ...' are useful. (Run them in ~/.vnc/certs)
-sslGenCA [dir] Generate your own Certificate Authority private key,
certificate, and other files in directory [dir].
x11vnc then exits.
If [dir] is not supplied, a -ssldir setting is used,
or otherwise ~/.vnc/certs is used.
This command also creates directories where server and
client certs and keys will be stored. The openssl(1)
program must be installed on the system and available
in PATH.
After the CA files and directories are created the
x11vnc command exits; the VNC server is not run.
You will be prompted for information to put into the CA
certificate. The info does not have to be accurate just
as long as clients accept the cert for VNC connections.
You will also need to supply a passphrase of at least
4 characters for the CA private key.
Once you have generated the CA you can distribute
its certificate part, [dir]/CA/cacert.pem, to other
workstations where VNC viewers will be run. One will
need to "import" this certificate in the applications,
e.g. Web browser, Java applet plugin, stunnel, etc.
Next, you can create and sign keys using the CA with
the -sslGenCert option below.
Examples:
x11vnc -sslGenCA
x11vnc -sslGenCA ~/myCAdir
x11vnc -ssldir ~/myCAdir -sslGenCA
(the last two lines are equivalent)
-sslGenCert type name Generate a VNC server or client certificate and private
key pair signed by the CA created previously with
-sslGenCA. The openssl(1) program must be installed
on the system and available in PATH.
After the Certificate is generated x11vnc exits; the
VNC server is not run.
The type of key to be generated is the string "type".
It is either "server" (i.e. for use by x11vnc) or
"client" (for a VNC viewer). Note that typically
only "server" is used: the VNC clients authenticate
themselves by a non-public-key method (e.g. VNC or
unix password). "type" is required.
An arbitrary default name you want to associate with
the key is supplied by the "name" string. You can
change it at the various prompts when creating the key.
"name" is optional.
If name is left blank for clients keys then "nobody"
is used. If left blank for server keys, then the
primary server key: "server.pem" is created (this
is the saved one referenced by "-ssl SAVE" when the
server is started)
If "name" begins with the string "self:" then
a self-signed certificate is created instead of one
signed by your CA key.
If "name" begins with the string "req:" then only a
key (.key) and a certificate signing *request* (.req)
are generated. You can then send the .req file to
an external CA (even a professional one, e.g. Thawte)
and then combine the .key and the received cert into
the .pem file with the same basename.
The distinction between "server" and "client" is
simply the choice of output filenames and sub-directory.
This makes it so the -ssl SAVE-name option can easily
pick up the x11vnc PEM file this option generates.
And similarly makes it easy for the -sslverify option
to pick up your client certs.
There is nothing special about the filename or directory
location of either the "server" and "client" certs.
You can rename the files or move them to wherever
you like.
Precede this option with -ssldir [dir] to use a
directory other than the default ~/.vnc/certs You will
need to run -sslGenCA on that directory first before
doing any -sslGenCert key creation.
Note you cannot recreate a cert with exactly the same
distiguished name (DN) as an existing one. To do so,
you will need to edit the [dir]/CA/index.txt file to
delete the line.
Similar to -sslGenCA, you will be prompted to fill
in some information that will be recorded in the
certificate when it is created.
Tip: if you know the fully-qualified hostname other
people will be connecting to, you can use that as the
CommonName "CN" to avoid some applications (e.g. web
browsers and java plugin) complaining that it does not
match the hostname.
You will also need to supply the CA private key
passphrase to unlock the private key created from
-sslGenCA. This private key is used to sign the server
or client certificate.
The "server" certs can be used by x11vnc directly by
pointing to them via the -ssl [pem] option. The default
file will be ~/.vnc/certs/server.pem. This one would
be used by simply typing -ssl SAVE. The pem file
contains both the certificate and the private key.
server.crt file contains the cert only.
The "client" cert + private key file will need
to be copied and imported into the VNC viewer
side applications (Web browser, Java plugin,
stunnel, etc.) Once that is done you can delete the
"client" private key file on this machine since
it is only needed on the VNC viewer side. The,
e.g. ~/.vnc/certs/clients/<name>.pem contains both
the cert and private key. The <name>.crt contains the
certificate only.
NOTE: It is very important to know one should
generate new keys with a passphrase. Otherwise if an
untrusted user steals the key file he could use it to
masquerade as the x11vnc server (or VNC viewer client).
You will be prompted whether to encrypt the key with
a passphrase or not. It is recommended that you do.
One inconvenience to a passphrase is that it must
be typed in EVERY time x11vnc or the client app is
started up.
Examples:
x11vnc -sslGenCert server
x11vnc -ssl SAVE -display :0 ...
and then on viewer using ss_vncviewer stunnel wrapper
(see the FAQ):
ss_vncviewer -verify ./cacert.crt hostname:0
(this assumes the cacert.crt cert from -sslGenCA
was safely copied to the VNC viewer machine where
ss_vncviewer is run)
Example using a name:
x11vnc -sslGenCert server charlie
x11vnc -ssl SAVE-charlie -display :0 ...
Example for a client certificate (rarely used):
[truncated]
Options (284)
| Option | Description | Source |
|---|---|---|
-display disp | X11 server display to connect to, usually :0. | help + man |
-auth file | Set the X authority file to be "file", equivalent to setting the XAUTHORITY environment variable to "file" before startup. | help + man |
-N | If the X display is :N, try to set the VNC display to also be :N This just sets the -rfbport option to 5900+N The program will exit immediately if that port is not available. | help + man |
-autoport n | Automatically probe for a free VNC port starting at n. | help + man |
-rfbport str | The VNC port to listen on (a LibVNCServer option), e.g. 5900, 5901, etc. | help + man |
-6 | IPv6 listening support. | help + man |
-no6 | Disable IPv6 listening support (only useful if the "-6" mode is compiled in to be the default; | help + man |
-noipv6 | Do not try to use IPv6 for any listening or connecting sockets. | help + man |
-noipv4 | Do not try to use IPv4 for any listening or connecting sockets. | help + man |
-reopen | If the X server connection is disconnected, try to reopen the X display (up to one time.) This is of use for display managers like GDM (KillInitClients option) that kill x11vnc just after the user… | help + man |
-reflect host:N | Instead of connecting to and polling an X display, connect to the remote VNC server host:N and be a reflector/repeater for it. | help + man |
-id windowid | Show the X window corresponding to "windowid" not the entire display. | help + man |
-sid windowid | As -id, but instead of using the window directly it shifts a root view to it: this shows SaveUnders menus, etc, although they will be clipped if they extend beyond the window. | help + man |
-appshare | Simple application sharing based on the -id/-sid mechanism. | help + man |
-clip WxH+X+Y | Only show the sub-region of the full display that corresponds to the rectangle geometry with size WxH and offset +X+Y. | help + man |
-flashcmap | In 8bpp indexed color, let the installed colormap flash as the pointer moves from window to window (slow). | help + man |
-shiftcmap n | Rare problem, but some 8bpp displays use less than 256 colorcells (e.g. 16-color grayscale, perhaps the other bits are used for double buffering) and also need to shift the pixels values away from 0,… | help + man |
-notruecolor | For 8bpp displays, force indexed color (i.e. a colormap) even if it looks like 8bpp TrueColor (rare problem). | help + man |
-advertise_truecolor | If the X11 display is indexed color, lie to clients when they first connect by telling them it is truecolor. | help + man |
-visual n | This option probably does not do what you think. | help + man |
-overlay | Handle multiple depth visuals on one screen, e.g. 8+24 and 24+8 overlay visuals (the 32 bits per pixel are packed with 8 for PseudoColor and 24 for TrueColor). | help + man |
-overlay_nocursor | Sets -overlay, but does not try to draw the exact mouse cursor shape using the overlay mechanism. | help + man |
-8to24 opts | Try this option if -overlay is not supported on your OS, and you have a legacy 8bpp app that you want to view on a multi-depth display with default depth 24 (and is 32 bpp) OR have a default depth 8… | help + man |
-24to32 | Very rare problem: if the framebuffer (X display or -rawfb) is 24bpp instead of the usual 32bpp, then dynamically transform the pixels to 32bpp. | help + man |
-scale fraction | Scale the framebuffer by factor "fraction". | help + man |
-geometry WxH | Same as -scale WxH | help + man |
-scale_cursor frac | By default if -scale is supplied the cursor shape is scaled by the same factor. | help + man |
-viewonly | All VNC clients can only watch (default off). | help + man |
-shared | VNC display is shared, i.e. more than one viewer can connect at the same time (default off). | help + man |
-once | Exit after the first successfully connected viewer disconnects, opposite of -forever. | help + man |
-forever | Keep listening for more connections rather than exiting as soon as the first client(s) disconnect. | help + man |
-loop | Create an outer loop restarting the x11vnc process whenever it terminates. | help + man |
-timeout n | Exit unless a client connects within the first n seconds after startup. | help + man |
-sleepin n | At startup sleep n seconds before proceeding (e.g. to allow redirs and listening clients to start up) | help + man |
-inetd | Launched by inetd(8): stdio instead of listening socket. | help + man |
-tightfilexfer | Enable the TightVNC file transfer extension. | help + man |
-ultrafilexfer | Note: to enable UltraVNC filetransfer and to get it to work you probably need to supply these LibVNCServer options: "-rfbversion 3.6 -permitfiletransfer" "-ultrafilexfer" is an alias for this… | help + man |
-http | Instead of using -httpdir (see below) to specify where the Java vncviewer applet is, have x11vnc try to *guess* where the directory is by looking relative to the program location and in standard… | help + man |
-http_ssl | As -http, but force lookup for ssl classes subdir. | help + man |
-avahi | Use the Avahi/mDNS ZeroConf protocol to advertise this VNC server to the local network. | help + man |
-mdns | Same as -avahi. | help + man |
-zeroconf | Same as -avahi. | help + man |
-connect string | For use with "vncviewer -listen" reverse connections. | help + man |
-connect_or_exit str | As with -connect, except if none of the reverse connections succeed, then x11vnc shuts down immediately | help + man |
-proxy string | Use proxy in string (e.g. host:port) as a proxy for making reverse connections (-connect or -connect_or_exit options). | help + man |
-vncconnect | Monitor the VNC_CONNECT X property set by the standard VNC program vncconnect(1). | help + man |
-novncconnect | VNC program vncconnect(1). | help |
-localhost | Basically the same as "-allow 127.0.0.1". | help + man |
-unixsock str | Listen on the unix socket (AF_UNIX) 'str' for connections. | help + man |
-listen6 str | When in IPv6 listen mode "-6", listen only on the network interface with address "str". | help + man |
-nolookup | Do not use gethostbyname() or gethostbyaddr() to look up host names or IP numbers. | help + man |
-input string | Fine tuning of allowed user input. | help + man |
-grabkbd | When VNC viewers are connected, attempt to the grab the keyboard so a (non-malicious) user sitting at the physical display is not able to enter keystrokes. | help + man |
-grabptr | As -grabkbd, but for the mouse pointer using XGrabPointer(3X11). | help + man |
-ungrabboth | Whenever there is any input (either keyboard or pointer), ungrab *both* the keyboard and the pointer while injecting the synthetic input. | help + man |
-grabalways | Apply both -grabkbd and -grabptr even when no VNC viewers are connected. | help + man |
-viewpasswd string | Supply a 2nd password for view-only logins. | help + man |
-passwdfile filename | Specify the LibVNCServer password via the first line of the file "filename" (instead of via -passwd on the command line where others might see it via ps(1)). | help + man |
-showrfbauth filename | Print to the screen the obscured VNC password kept in the rfbauth file "filename" and then exit. | help + man |
-unixpw list | Use Unix username and password authentication. | help + man |
-unixpw_nis list | As -unixpw above, however do not use su(1) but rather use the traditional getpwnam(3) + crypt(3) method to verify passwords. | help + man |
-unixpw_cmd cmd | As -unixpw above, however do not use su(1) but rather run the externally supplied command "cmd". | help + man |
-find | Find the user's display using FINDDISPLAY. | help + man |
-finddpy | Run the FINDDISPLAY program, print out the found display (if any) and exit. | help + man |
-listdpy | Have the FINDDISPLAY program list all of your displays (i.e. all the X displays on the local machine that you have access rights to). | help + man |
-findauth disp | Apply the -find/-finddpy heuristics to try to guess the XAUTHORITY file for DISPLAY 'disp'. | help + man |
-create | First try to find the user's display using FINDDISPLAY, if that doesn't succeed create an X session via the FINDCREATEDISPLAY method. | help + man |
-xdummy | As in -create, except Xdummy instead of Xvfb. | help + man |
-xvnc | As in -create, except Xvnc instead of Xvfb. | help + man |
-xvnc_redirect | As in -create, except Xvnc.redirect instead of Xvfb. | help + man |
-xdummy_xvfb | Sets WAIT:cmd=FINDCREATEDISPLAY-Xdummy,Xvfb | help + man |
-create_xsrv str | Sets WAIT:cmd=FINDCREATEDISPLAY-<str> Can be on cmdline after anything that sets WAIT:.. | help + man |
-svc | Terminal services mode based on SSL access. | help + man |
-svc_xdummy | As -svc except Xdummy instead of Xvfb. | help + man |
-svc_xvnc | As -svc except Xvnc instead of Xvfb. | help + man |
-svc_xdummy_xvfb | As -svc with Xdummy,Xvfb. | help + man |
-xdmsvc | Display manager Terminal services mode based on SSL. | help + man |
-sshxdmsvc | Display manager Terminal services mode based on SSH. | help + man |
-redirect port | As in FINDCREATEDISPLAY-Xvnc.redirect mode except redirect immediately (i.e. without X session finding or creation) to a VNC server listening on port. | help + man |
-vencrypt mode | The VeNCrypt extension to the VNC protocol allows encrypted SSL/TLS connections. | help + man |
-anontls mode | The ANONTLS extension to the VNC protocol allows encrypted SSL/TLS connections. | help + man |
-sslonly | Same as: "-vencrypt never -anontls never" i.e. it disables the VeNCrypt and ANONTLS encryption methods and only allows standard SSL tunneling. | help + man |
-dhparams file | For some operations a set of Diffie Hellman parameters (prime and generator) is needed. | help + man |
-nossl | Disable the -ssl option (see below). | help + man |
-ssl pem | Use the openssl library (www.openssl.org) to provide a built-in encrypted SSL/TLS tunnel between VNC viewers and x11vnc. | help + man |
-ssltimeout n | Set SSL read timeout to n seconds. | help + man |
-sslnofail | Exit at the first SSL connection failure. | help + man |
-ssldir dir | Use "dir" as an alternate ssl certificate and key management toplevel directory. | help + man |
-sslverify path | For either of the -ssl or -stunnel modes, use "path" to provide certificates to authenticate incoming VNC *Client* connections (normally only the server is authenticated in SSL.) This can be used as… | help + man |
-sslCRL path | Set the Certificate Revocation Lists (CRL) to "path". | help + man |
-sslGenCA dir | Generate your own Certificate Authority private key, certificate, and other files in directory [dir]. | help + man |
-sslGenCert type | Generate a VNC server or client certificate and private key pair signed by the CA created previously with -sslGenCA. | help + man |
-allow host1 | Only allow client connections from hosts matching the comma separated list of hostnames or IP addresses. (in the manual page but not in --help) | man |
-unixpw_system_greeter | Present a "Press 'Escape' for System Greeter" option to the connecting VNC client in combined -unixpw and xdmcp FINDCREATEDISPLAY modes (e.g. -xdmsvc). (in the manual page but not in --help) | man |
-sslEncKey pem | Utility to encrypt an existing PEM file with a passphrase you supply when prompted. (in the manual page but not in --help) | man |
-sslCertInfo pem | Prints out information about an existing PEM file. (in the manual page but not in --help) | man |
-sslDelCert pem | Prompts you to delete all .crt .pem .key .req files associated with [pem]. (in the manual page but not in --help) | man |
-sslScripts | Prints out both the 'genCA' and 'genCert' x11vnc openssl wrapper scripts for you to examine, modify, etc. (in the manual page but not in --help) | man |
-stunnel pem | Use the stunnel(8) (stunnel.mirt.net) to provide an encrypted SSL tunnel between viewers and x11vnc. (in the manual page but not in --help) | man |
-stunnel3 pem | Use version 3.x stunnel command line syntax instead of version 4.x. (in the manual page but not in --help) | man |
-enc cipher:keyfile | Use symmetric encryption with cipher "cipher" and secret key data in "keyfile". (in the manual page but not in --help) | man |
-https port | Use a special, separate HTTPS port (-ssl and -stunnel modes only) for HTTPS Java viewer applet downloading. (in the manual page but not in --help) | man |
-httpsredir port | In -ssl mode with the Java applet retrieved via HTTPS, when the HTML file containing applet parameters ('index.vnc' or 'proxy.vnc') is sent do NOT set the applet PORT parameter to the actual VNC port… (in the manual page but not in --help) | man |
-http_oneport | For UN-encrypted connections mode (i.e. no -ssl, -stunnel, or -enc options), allow the Java VNC Viewer applet to be downloaded thru the VNC port via HTTP. (in the manual page but not in --help) | man |
-ssh user@host:disp | Create a remote listening port on machine "host" via a SSH tunnel using the -R rport:localhost:lport method. (in the manual page but not in --help) | man |
-usepw | If no other password method was supplied on the command line, first look for ~/.vnc/passwd and if found use it with -rfbauth; (in the manual page but not in --help) | man |
-storepasswd pass | Store password pass as the VNC password in the file file. (in the manual page but not in --help) | man |
-nopw | Disable the big warning message when you use x11vnc without some sort of password. (in the manual page but not in --help) | man |
-accept string | Run a command (possibly to prompt the user at the X11 display) to decide whether an incoming client should be allowed to connect or not. (in the manual page but not in --help) | man |
-afteraccept string | As -accept, except to run a user supplied command after a client has been accepted and authenticated. (in the manual page but not in --help) | man |
-gone string | As -accept, except to run a user supplied command when a client goes away (disconnects). (in the manual page but not in --help) | man |
-users list | If x11vnc is started as root (say from inetd(8) or from display managers xdm(1) , gdm(1) , etc), then as soon as possible after connections to the X display are established try to switch to one of… (in the manual page but not in --help) | man |
-noshm | Do not use the MIT-SHM extension for the polling. (in the manual page but not in --help) | man |
-flipbyteorder | Sometimes needed if remotely polled host has different endianness. (in the manual page but not in --help) | man |
-onetile | Do not use the new copy_tiles() framebuffer mechanism, just use 1 shm tile for polling. (in the manual page but not in --help) | man |
-solid color | To improve performance, when VNC clients are connected try to change the desktop background to a solid color. (in the manual page but not in --help) | man |
-blackout string | Black out rectangles on the screen. (in the manual page but not in --help) | man |
-xinerama, -noxinerama | If your screen is composed of multiple monitors glued together via XINERAMA, and that screen is not a rectangle this option will try to guess the areas to black out (if your system has libXinerama). (in the manual page but not in --help) | man |
-xtrap | Use the DEC-XTRAP extension for keystroke and mouse input insertion. (in the manual page but not in --help) | man |
-xrandr mode | If the display supports the XRANDR (X Resize, Rotate and Reflection) extension, and you expect XRANDR events to occur to the display while x11vnc is running, this options indicates x11vnc should try… (in the manual page but not in --help) | man |
-rotate string | Rotate and/or flip the framebuffer view exported by VNC. (in the manual page but not in --help) | man |
-padgeom WxH | Whenever a new vncviewer connects, the framebuffer is replaced with a fake, solid black one of geometry WxH. (in the manual page but not in --help) | man |
-o logfile | Write stderr messages to file logfile instead of to the terminal. (in the manual page but not in --help) | man |
-flag file | Write the "PORT=NNNN" (e.g. PORT=5900) string to file in addition to stdout. (in the manual page but not in --help) | man |
-rmflag file | Remove file at exit to signal when x11vnc is done. (in the manual page but not in --help) | man |
-rc filename | Use filename instead of $HOME/.x11vncrc for rc file. (in the manual page but not in --help) | man |
-norc | Do not process any .x11vncrc file for options. (in the manual page but not in --help) | man |
-env VAR=VALUE | Set the environment variable 'VAR' to value 'VALUE' at x11vnc startup. (in the manual page but not in --help) | man |
-prog /path/to/x11vnc | Set the full path to the x11vnc program for cases when it cannot be determined from argv[0] (e.g. tcpd/inetd) (in the manual page but not in --help) | man |
-h, -help | Print this help text. (in the manual page but not in --help) | man |
-V, -version | Print program version and last modification date. (in the manual page but not in --help) | man |
-license | Print out license information. (in the manual page but not in --help) | man |
-dbg | Instead of exiting after cleaning up, run a simple "debug crash shell" when fatal errors are trapped. (in the manual page but not in --help) | man |
-q, -quiet | Be quiet by printing less informational output to stderr. (in the manual page but not in --help) | man |
-v, -verbose | Print out more information to stderr. (in the manual page but not in --help) | man |
-bg | Go into the background after screen setup. (in the manual page but not in --help) | man |
-modtweak, -nomodtweak | Option -modtweak automatically tries to adjust the AltGr and Shift modifiers for differing language keyboards between client and host. (in the manual page but not in --help) | man |
-xkb, -noxkb | When in modtweak mode, use the XKEYBOARD extension (if the X display supports it) to do the modifier tweaking. (in the manual page but not in --help) | man |
-capslock | When in -modtweak (the default) or -xkb mode, if a keysym in the range A-Z comes in check the X server to see if the Caps_Lock is set. (in the manual page but not in --help) | man |
-skip_lockkeys, -noskip_lockkeys | Have x11vnc ignore all Caps_Lock, Shift_Lock, Num_Lock, Scroll_Lock keysyms received from viewers. (in the manual page but not in --help) | man |
-skip_keycodes string | Ignore the comma separated list of decimal keycodes. (in the manual page but not in --help) | man |
-sloppy_keys | Experimental option that tries to correct some "sloppy" key behavior. (in the manual page but not in --help) | man |
-skip_dups, -noskip_dups | Some VNC viewers send impossible repeated key events, e.g. key-down, key-down, key-up, key-up all for the same key, or 20 downs in a row for the same modifier key! Setting -skip_dups means to skip… (in the manual page but not in --help) | man |
-add_keysyms, -noadd_keysyms | If a Keysym is received from a VNC viewer and that Keysym does not exist in the X server, then add the Keysym to the X server's keyboard mapping on an unused key. (in the manual page but not in --help) | man |
-clear_mods | At startup and exit clear the modifier keys by sending KeyRelease for each one. (in the manual page but not in --help) | man |
-clear_keys | As -clear_mods, except try to release ANY pressed key. (in the manual page but not in --help) | man |
-clear_all | As -clear_keys, except try to release any CapsLock, NumLock, etc. (in the manual page but not in --help) | man |
-remap string | Read Keysym remappings from file named string. (in the manual page but not in --help) | man |
-norepeat, -repeat | Option -norepeat disables X server key auto repeat when VNC clients are connected and VNC keyboard input is not idle for more than 5 minutes. (in the manual page but not in --help) | man |
-nofb | Ignore video framebuffer: only process keyboard and pointer. (in the manual page but not in --help) | man |
-nobell | Do not watch for XBell events. (in the manual page but not in --help) | man |
-nosel | Do not manage exchange of X selection/cutbuffer between VNC viewers and the X server at all. (in the manual page but not in --help) | man |
-noprimary | Do not poll the PRIMARY selection for changes to send back to clients. (in the manual page but not in --help) | man |
-nosetprimary | Do not set the PRIMARY selection for changes received from VNC clients. (in the manual page but not in --help) | man |
-noclipboard | Do not poll the CLIPBOARD selection for changes to send back to clients. (in the manual page but not in --help) | man |
-nosetclipboard | Do not set the CLIPBOARD selection for changes received from VNC clients. (in the manual page but not in --help) | man |
-seldir string | If direction string is "send", only send the selection to viewers, and if it is "recv" only receive it from viewers. (in the manual page but not in --help) | man |
-cursor, -nocursor mode | Sets how the pointer cursor shape (little icon at the mouse pointer) should be handled. (in the manual page but not in --help) | man |
-cursor_drag | Show cursor shape changes even when the mouse is being dragged with a mouse button down. (in the manual page but not in --help) | man |
-arrow n | Choose an alternate "arrow" cursor from a set of some common ones. (in the manual page but not in --help) | man |
-noxfixes | Do not use the XFIXES extension to draw the exact cursor shape even if it is available. (in the manual page but not in --help) | man |
-alphacut n | When using the XFIXES extension for the cursor shape, cursors with transparency will not usually be displayed exactly (but opaque ones will). (in the manual page but not in --help) | man |
-alphafrac fraction | With the threshold in -alphacut some cursors will become almost completely transparent because their alpha values are not high enough. (in the manual page but not in --help) | man |
-alpharemove | By default, XFIXES cursors pixels with transparency have the alpha factor multiplied into the RGB color values (i.e. that corresponding to blending the cursor with a black background). (in the manual page but not in --help) | man |
-noalphablend | In XFIXES mode do not send cursor alpha channel data to LibVNCServer. (in the manual page but not in --help) | man |
-nocursorshape | Do not use the TightVNC CursorShapeUpdates extension even if clients support it. (in the manual page but not in --help) | man |
-cursorpos, -nocursorpos | Option -cursorpos enables sending the X cursor position back to all vnc clients that support the TightVNC CursorPosUpdates extension. (in the manual page but not in --help) | man |
-xwarppointer, -noxwarppointer | Move the pointer with XWarpPointer(3X) instead of the XTEST extension. (in the manual page but not in --help) | man |
-always_inject | Even if there is no displacement (dx = dy = 0) for a VNC mouse event force the pointer to the indicated x,y position anyway. (in the manual page but not in --help) | man |
-buttonmap string | String to remap mouse buttons. (in the manual page but not in --help) | man |
-nodragging | Do not update the display during mouse dragging events (mouse button held down). (in the manual page but not in --help) | man |
-ncache n | Client-side caching scheme. (in the manual page but not in --help) | man |
-ncache_cr | In -ncache mode, try to do copyrect opaque window moves/drags instead of wireframes (this can induce painting errors). (in the manual page but not in --help) | man |
-ncache_no_moveraise | In -ncache mode, do not assume that moving a window will cause the window manager to raise it to the top of the stack. (in the manual page but not in --help) | man |
-ncache_no_dtchange | In -ncache mode, do not try to guess when the desktop (viewport) changes to another one (i.e. another workarea). (in the manual page but not in --help) | man |
-ncache_no_rootpixmap | In -ncache mode, do not try to snapshot the desktop background to use in guessing or reconstructing window save-unders. (in the manual page but not in --help) | man |
-ncache_keep_anims | In -ncache mode, do not try to disable window manager animations and other effects (that usually degrade ncache performance or cause painting errors). (in the manual page but not in --help) | man |
-ncache_old_wm | In -ncache mode, enable some heuristics for old style window managers such as fvwm and twm. (in the manual page but not in --help) | man |
-ncache_pad n | In -ncache mode, pad each window with n pixels for the caching rectangles. (in the manual page but not in --help) | man |
-debug_ncache | Turn on debugging and profiling output under -ncache. (in the manual page but not in --help) | man |
-wireframe, -nowireframe str | Try to detect window moves or resizes when a mouse button is held down and show a wireframe instead of the full opaque window. (in the manual page but not in --help) | man |
-nowireframelocal | By default, mouse motion and button presses of a user sitting at the LOCAL display are monitored for wireframing opportunities (so that the changes will be sent efficiently to the VNC clients). (in the manual page but not in --help) | man |
-wirecopyrect, -nowirecopyrect mode | Since the -wireframe mechanism evidently tracks moving windows accurately, a speedup can be obtained by telling the VNC viewers to locally copy the translated window region. (in the manual page but not in --help) | man |
-debug_wireframe | Turn on debugging info printout for the wireframe heuristics. (in the manual page but not in --help) | man |
-scrollcopyrect, -noscrollcopyrect mode | Like -wirecopyrect, but use heuristics to try to guess if a window has scrolled its contents (either vertically or horizontally). (in the manual page but not in --help) | man |
-scr_area n | Set the minimum area in pixels for a rectangle to be considered for the -scrollcopyrect detection scheme. (in the manual page but not in --help) | man |
-scr_skip list | Skip scroll detection for applications matching the comma separated list of strings in list. (in the manual page but not in --help) | man |
-scr_inc list | Opposite of -scr_skip: this list is consulted first and if there is a match the window will be monitored via RECORD for scrolls irrespective of -scr_skip. (in the manual page but not in --help) | man |
-scr_keys list | For keystroke scroll detection, only apply the RECORD heuristics to the comma separated list of keysyms in list. (in the manual page but not in --help) | man |
-scr_term list | Yet another cosmetic kludge. (in the manual page but not in --help) | man |
-scr_keyrepeat lo-hi | If a key is held down (or otherwise repeats rapidly) and this induces a rapid sequence of scrolls (e.g. holding down an Arrow key) the "scrollcopyrect" detection and overhead may not be able to keep… (in the manual page but not in --help) | man |
-scr_parms string | Set various parameters for the scrollcopyrect mode. (in the manual page but not in --help) | man |
-fixscreen string | Periodically "repair" the screen based on settings in string. (in the manual page but not in --help) | man |
-debug_scroll | Turn on debugging info printout for the scroll heuristics. (in the manual page but not in --help) | man |
-noxrecord | Disable any use of the RECORD extension. (in the manual page but not in --help) | man |
-grab_buster, -nograb_buster | Some of the use of the RECORD extension can leave a tiny window for XGrabServer deadlock. (in the manual page but not in --help) | man |
-debug_grabs | Turn on debugging info printout with respect to XGrabServer() deadlock for -scrollcopyrect__mode_. (in the manual page but not in --help) | man |
-debug_sel | Turn on debugging info printout with respect to PRIMARY, CLIPBOARD, and CUTBUFFER0 selections. (in the manual page but not in --help) | man |
-pointer_mode n | Various pointer motion update schemes. (in the manual page but not in --help) | man |
-input_skip n | For the pointer handling when non-threaded: try to read n user input events before scanning display. (in the manual page but not in --help) | man |
-allinput | Have x11vnc read and process all available client input before proceeding. (in the manual page but not in --help) | man |
-input_eagerly | Similar to -allinput but use the handleEventsEagerly mechanism built into LibVNCServer. (in the manual page but not in --help) | man |
-multiptr | Enable support for per-client input devices. (in the manual page but not in --help) | man |
-speeds rd | x11vnc tries to estimate some speed parameters that are used to optimize scheduling (e.g. -pointer_mode 4, -wireframe, -scrollcopyrect) and other things. (in the manual page but not in --help) | man |
-wmdt string | For some features, e.g. -wireframe and -scrollcopyrect, x11vnc has to work around issues for certain window managers or desktops (currently kde and xfce). (in the manual page but not in --help) | man |
-debug_pointer | Print debugging output for every pointer event. (in the manual page but not in --help) | man |
-debug_keyboard | Print debugging output for every keyboard event. (in the manual page but not in --help) | man |
-defer time | Time in ms to delay sending updates to connected clients (deferUpdateTime) Default: 20 (in the manual page but not in --help) | man |
-wait time | Time in ms to pause between screen polls. (in the manual page but not in --help) | man |
-extra_fbur n | Perform extra FrameBufferUpdateRequests checks to try to be in better sync with the client's requests. (in the manual page but not in --help) | man |
-wait_ui factor | Factor by which to cut the -wait time if there has been recent user input (pointer or keyboard). (in the manual page but not in --help) | man |
-setdefer n | When the -wait_ui mechanism cuts down the wait time ms, set the defer time to the same ms value. (in the manual page but not in --help) | man |
-nowait_bog | Do not detect if the screen polling is "bogging down" and sleep more. (in the manual page but not in --help) | man |
-slow_fb time | Floating point time in seconds to delay all screen polling. (in the manual page but not in --help) | man |
-xrefresh time | Floating point time in seconds to indicate how often to do the equivalent of xrefresh(1) to force all windows (in the viewable area if -id, -sid, or -clip is used) to repaint themselves. (in the manual page but not in --help) | man |
-nap, -nonap | Monitor activity and if it is low take longer naps between screen polls to really cut down load when idle. (in the manual page but not in --help) | man |
-sb time | Time in seconds after NO activity (e.g. screen blank) to really throttle down the screen polls (i.e. sleep for about 1.5 secs). (in the manual page but not in --help) | man |
-readtimeout n | Set LibVNCServer rfbMaxClientWait to n seconds. (in the manual page but not in --help) | man |
-ping n | Send a 1x1 framebuffer update to all clients every n seconds (e.g. to try to keep a network connection alive) (in the manual page but not in --help) | man |
-nofbpm, -fbpm | If the system supports the FBPM (Frame Buffer Power Management) extension (i.e. some Sun systems), then prevent the video h/w from going into a reduced power state when VNC clients are connected. (in the manual page but not in --help) | man |
-nodpms, -dpms | If the system supports the DPMS (Display Power Management Signaling) extension, then prevent the monitor from going into a reduced power state when VNC clients are connected. (in the manual page but not in --help) | man |
-forcedpms | If the system supports the DPMS (Display Power Management Signaling) extension, then try to keep the monitor in a powered off state. (in the manual page but not in --help) | man |
-clientdpms | As -forcedpms but only when VNC clients are connected. (in the manual page but not in --help) | man |
-noserverdpms | The UltraVNC ServerInput extension is supported. (in the manual page but not in --help) | man |
-noultraext | Disable the following UltraVNC extensions: SingleWindow and ServerInput. (in the manual page but not in --help) | man |
-chatwindow | Place a local UltraVNC chat window on the X11 display that x11vnc is polling. (in the manual page but not in --help) | man |
-noxdamage | Do not use the X DAMAGE extension to detect framebuffer changes even if it is available. (in the manual page but not in --help) | man |
-xd_area A | Set the largest DAMAGE rectangle area A (in pixels: width height) to trust as truly damaged: the rectangle will be copied from the framebuffer (slow) no matter what. (in the manual page but not in --help) | man |
-xd_mem f | Set how long DAMAGE rectangles should be "remembered", f is a floating point number and is in units of the scanline repeat cycle time (32 iterations). (in the manual page but not in --help) | man |
-sigpipe string | Broken pipe (SIGPIPE) handling. (in the manual page but not in --help) | man |
-threads, -nothreads | Whether or not to use the threaded LibVNCServer algorithm [rfbRunEventLoop] if libpthread is available. (in the manual page but not in --help) | man |
-fs f | If the fraction of changed tiles in a poll is greater than f, the whole screen is updated. (in the manual page but not in --help) | man |
-gaps n | Heuristic to fill in gaps in rows or cols of n or less tiles. (in the manual page but not in --help) | man |
-grow n | Heuristic to grow islands of changed tiles n or wider by checking the tile near the boundary. (in the manual page but not in --help) | man |
-fuzz n | Tolerance in pixels to mark a tiles edges as changed. (in the manual page but not in --help) | man |
-debug_tiles | Print debugging output for tiles, fb updates, etc. (in the manual page but not in --help) | man |
-snapfb | Instead of polling the X display framebuffer (fb) for changes, periodically copy all of X display fb into main memory and examine that copy for changes. (in the manual page but not in --help) | man |
-rawfb string | Instead of polling X, poll the memory object specified in string. (in the manual page but not in --help) | man |
-freqtab file | For use with "-rawfb video" for TV tuner devices to specify station frequencies. (in the manual page but not in --help) | man |
-pipeinput cmd | This option lets you supply an external command in cmd that x11vnc will pipe all of the user input events to in a simple format. (in the manual page but not in --help) | man |
-macnodim | For the native MacOSX server, disable dimming. (in the manual page but not in --help) | man |
-macnosleep | For the native MacOSX server, disable display sleep. (in the manual page but not in --help) | man |
-macnosaver | For the native MacOSX server, disable screensaver. (in the manual page but not in --help) | man |
-macnowait | For the native MacOSX server, do not wait for the user to switch back to his display. (in the manual page but not in --help) | man |
-macwheel n | For the native MacOSX server, set the mouse wheel speed to n (default 5). (in the manual page but not in --help) | man |
-macnoswap | For the native MacOSX server, do not swap mouse buttons 2 and 3. (in the manual page but not in --help) | man |
-macnoresize | For the native MacOSX server, do not resize or reset the framebuffer even if it is detected that the screen resolution or depth has changed. (in the manual page but not in --help) | man |
-maciconanim n | For the native MacOSX server, set n to the number of milliseconds that the window iconify/deiconify animation takes. (in the manual page but not in --help) | man |
-macmenu | For the native MacOSX server, in -ncache client-side caching mode, try to cache pull down menus (not perfect because they have animated fades, etc.) (in the manual page but not in --help) | man |
-macuskbd | For the native MacOSX server, use the original keystroke insertion code based on a US keyboard. (in the manual page but not in --help) | man |
-macnoopengl | For the native MacOSX server, do not use OpenGL for screen capture, but rather use the original, deprecated raw memory access method: addr = CGDisplayBaseAddress(). (in the manual page but not in --help) | man |
-macnorawfb | For the native MacOSX server, disable the raw memory address screen capture method. (in the manual page but not in --help) | man |
-gui gui-opts | Start up a simple tcl/tk gui based on the remote control options -remote/-query described below. (in the manual page but not in --help) | man |
-remote command | Remotely control some aspects of an already running x11vnc server. (in the manual page but not in --help) | man |
-query variable | Like -remote, except just query the value of variable. (in the manual page but not in --help) | man |
-QD variable | Just like -query variable, but returns the default value for that parameter (no running x11vnc server is consulted) (in the manual page but not in --help) | man |
-sync | By default -remote commands are run asynchronously, that is, the request is posted and the program immediately exits. (in the manual page but not in --help) | man |
-query_retries str | If a query fails to get a response from an x11vnc server, retry up to n times. (in the manual page but not in --help) | man |
-remote_prefix str | Enable a remote-control communication channel for connected VNC clients. (in the manual page but not in --help) | man |
-noremote, -yesremote | Do not process any remote control commands or queries. (in the manual page but not in --help) | man |
-unsafe | A few remote commands are disabled by default (currently: id:pick, accept:<cmd>, gone:<cmd>, and rawfb:setup:<cmd>) because they are associated with running external programs. (in the manual page but not in --help) | man |
-safer | Equivalent to: -novncconnect -noremote and prohibiting -gui and the -connect file. (in the manual page but not in --help) | man |
-privremote | Perform some sanity checks and disable remote-control commands if it appears that the X DISPLAY and/or connectfile can be accessed by other users. (in the manual page but not in --help) | man |
-nocmds | No external commands (e.g. system(3) , popen(3) , exec(3) ) will be run at all. (in the manual page but not in --help) | man |
-allowedcmds list | list contains a comma separated list of the only external commands that can be run. (in the manual page but not in --help) | man |
-deny_all | For use with -remote nodeny: start out denying all incoming clients until "-remote nodeny" is used to let them in. (in the manual page but not in --help) | man |
-rfbwait time | max time in ms to wait for RFB client (in the manual page but not in --help) | man |
-rfbauth passwd-file | use authentication on RFB protocol (use 'x11vnc -storepasswd pass file' to create a password file) (in the manual page but not in --help) | man |
-rfbversion 3.x | Set the version of the RFB we choose to advertise (in the manual page but not in --help) | man |
-permitfiletransfer | permit file transfer support (in the manual page but not in --help) | man |
-passwd plain-password | use authentication (use plain-password as password, USE AT YOUR RISK) (in the manual page but not in --help) | man |
-deferupdate time | time in ms to defer updates (default 40) (in the manual page but not in --help) | man |
-deferptrupdate time | time in ms to defer pointer updates (default none) (in the manual page but not in --help) | man |
-desktop name | VNC desktop name (default "LibVNCServer") (in the manual page but not in --help) | man |
-alwaysshared | always treat new clients as shared (in the manual page but not in --help) | man |
-nevershared | never treat new clients as shared (in the manual page but not in --help) | man |
-dontdisconnect | don't disconnect existing clients when a new non-shared connection comes in (refuse new connection instead) (in the manual page but not in --help) | man |
-httpdir dir-path | enable http server using dir-path home (in the manual page but not in --help) | man |
-httpport portnum | use portnum for http connection (in the manual page but not in --help) | man |
-enablehttpproxy | enable http proxy support (in the manual page but not in --help) | man |
-progressive height | enable progressive updating for slow links (in the manual page but not in --help) | man |
-listen ipaddr | listen for connections only on network interface with addr ipaddr. (in the manual page but not in --help) | man |
-disablefiletransfer | disable file transfer (in the manual page but not in --help) | man |
-ftproot string | set ftp root (in the manual page but not in --help) | man |