| SYSTEMD-FSTAB-GENERATOR(8) | systemd-fstab-generator | SYSTEMD-FSTAB-GENERATOR(8) |
.SH "NAME" systemd-fstab-generator - Unit generator for
/etc/fstab
.SH "SYNOPSIS"
.PP /usr/lib/systemd/system-generators/systemd-fstab-generator
.SH "DESCRIPTION"
.PP systemd-fstab-generator is a generator that translates /etc/fstab (see
fstab(5) for details) into native systemd units early at boot and
when configuration of the system manager is reloaded. This will instantiate
mount and swap units as necessary.
.PP The passno field is treated like a simple boolean, and the
ordering information is discarded. However, if the root file system is
checked, it is checked before all the other file systems.
.PP See systemd.mount(5) and systemd.swap(5) for more
information about special /etc/fstab mount options this generator
understands.
.PP One special topic is handling of symbolic links. Historical init
implementations supported symlinks in /etc/fstab. Because mount units will
refuse mounts where the target is a symbolic link, this generator will
resolve any symlinks as far as possible when processing /etc/fstab in order
to enhance backwards compatibility. If a symlink target does not exist at
the time that this generator runs, it is assumed that the symlink target is
the final target of the mount.
.PP systemd-fstab-generator implements systemd.generator(7).
.SH "KERNEL COMMAND LINE"
.PP systemd-fstab-generator understands the following kernel command line
parameters:
.PP fstab=, rd.fstab=
Takes a boolean argument. Defaults to yes. If no, causes the generator to
ignore any mounts or swap devices configured in /etc/fstab. rd.fstab=
is honored only in the initrd, while fstab= is honored by both the
main system and the initrd.
Added in version 186.
.RE
.PP root=
Configures the operating system's root filesystem to mount when running in
the initrd. This accepts a device node path (usually /dev/disk/by-uuid/...
or /dev/disk/by-label/... or similar), or the special values gpt-auto,
gpt-auto-force, dissect, dissect-force, fstab, tmpfs, bind:..., and off.
Set to gpt-auto, gpt-auto-force, dissect, dissect-force to explicitly request
automatic root file system discovery, implemented in
systemd-gpt-auto-generator(8).
Use fstab to explicitly request automatic root file system discovery via the
initrd /etc/fstab rather than via kernel command line.
Use tmpfs in order to mount a tmpfs(5) file system as root file system
of the OS. This is useful in combination with mount.usr= (see below)
in order to combine a volatile root file system with a separate, immutable
/usr/ file system. Also see systemd.volatile= below.
Use bind:... to bind mount another directory as operating system root
filesystems (added in v258). Expects an absolute path name referencing an
existing directory within the initrd's file hierarchy to boot into. Since
the resulting root file system is supposed to behave like a regular OS root,
the bind mount is established with the dev, suid and
exec options (i.e. the nodev, nosuid and noexec
flags that would otherwise be inherited from the file system the source
directory resides on, such as /run/, are cleared), unless overridden via
rootflags=.
Set to off to turn off mounting of a root file system.
Note that further root= values may be supported, implemented in
additional packages.
Added in version 217.
.RE
.PP rootfstype=
Takes the root filesystem type that will be passed to the mount command.
rootfstype= is honored by the initrd.
Added in version 217.
.RE
.PP rootflags=
Takes the root filesystem mount options to use. rootflags= is honored
by the initrd.
Note that unlike most kernel command line options this setting does not
override settings made in configuration files (specifically: the mount
option string in /etc/fstab). See systemd-remount-fs.service(8).
Added in version 217.
.RE
.PP mount.usr=
Takes the /usr/ filesystem to be mounted by the initrd. If
mount.usrfstype= or mount.usrflags= is set, then the mount
configured via mount.usr= will default to the same value set in
root=.
Set to dissect to explicitly request automatic /usr/ file system discovery,
implemented in systemd-gpt-auto-generator(8).
Set to off to turn off mounting of a separate /usr/ file system.
mount.usr= is honored by the initrd.
Added in version 217.
.RE
.PP mount.usrfstype=
Takes the /usr/ filesystem type that will be passed to the mount command. If
mount.usr= or mount.usrflags= is set, then
mount.usrfstype= will default to the value set in
rootfstype=.
Otherwise, this value will be read from the /usr/ entry in /etc/fstab on the
root filesystem.
mount.usrfstype= is honored by the initrd.
Added in version 217.
.RE
.PP mount.usrflags=
Takes the /usr/ filesystem mount options to use. If mount.usr= or
mount.usrfstype= is set, then mount.usrflags= will default to
the value set in rootflags=.
Otherwise, this value will be read from the /usr/ entry in /etc/fstab on the
root filesystem.
mount.usrflags= is honored by the initrd.
Added in version 217.
.RE
.PP roothash=, usrhash=
These options are primarily read by systemd-veritysetup-generator(8).
When set this indicates that the root file system (or /usr/) shall be
mounted from Verity volumes with the specified hashes. If these kernel
command line options are set the root (or /usr/) file system is thus mounted
from a device mapper volume /dev/mapper/root (or /dev/mapper/usr).
Added in version 251.
.RE
.PP systemd.volatile=
Controls whether the system shall boot up in volatile mode. Takes a boolean
argument or the special values state and overlay.
If no (the default), this generator makes no changes to the mount tree and
the system is booted up in normal mode.
If yes the generator ensures systemd-volatile-root.service(8) is run
in the initrd. This service changes the mount table before transitioning to
the host system, so that a volatile memory file system (tmpfs) is used as
root directory, with only /usr/ mounted into it from the configured root
file system, in read-only mode. This way the system operates in fully
stateless mode, with all configuration and state reset at boot and lost at
shutdown, as /etc/ and /var/ will be served from the (initially unpopulated)
volatile memory file system.
If set to state the generator will leave the root directory mount point
unaltered, however will mount a tmpfs file system to /var/. In this mode the
normal system configuration (i.e. the contents of /etc/) is in effect (and
may be modified during system runtime), however the system state (i.e. the
contents of /var/) is reset at boot and lost at shutdown.
If this setting is set to overlay the root file system is set up as overlayfs
mount combining the read-only root directory with a writable tmpfs, so that
no modifications are made to disk, but the file system may be modified
nonetheless with all changes being lost at reboot.
Note that in none of these modes the root directory, /etc/, /var/ or any
other resources stored in the root file system are physically removed. It's
thus safe to boot a system that is normally operated in non-volatile mode
temporarily into volatile mode, without losing data.
Note that with the exception of overlay mode, enabling this setting will only
work correctly on operating systems that can boot up with only /usr/
mounted, and are able to automatically populate /etc/, and also /var/ in
case of systemd.volatile=yes.
Also see root=tmpfs above, for a method to combine a tmpfs file system
with a regular /usr/ file system (as configured via mount.usr=). The
main distinction between systemd.volatile=yes, and root=tmpfs
in combination mount.usr= is that the former operates on top of a
regular root file system and temporarily obstructs the files and directories
above its /usr/ subdirectory, while the latter does not hide any files, but
simply mounts a unpopulated tmpfs as root file system and combines it with a
user picked /usr/ file system.
Added in version 233.
.RE
.PP systemd.swap=
Takes a boolean argument or enables the option if specified without an
argument. If disabled, causes the generator to ignore any swap devices
configured in /etc/fstab. Defaults to enabled.
Added in version 246.
.RE
.PP
systemd.mount-extra=WHAT:WHERE[:FSTYPE[:OPTIONS]],
rd.systemd.mount-extra=WHAT:WHERE[:FSTYPE[:OPTIONS]]
Specifies the mount unit. Takes at least two and at most four fields
separated with a colon (:). Each field is handled as the corresponding fstab
field. This option can be specified multiple times.
rd.systemd.mount-extra= is honored only in the initrd, while
systemd.mount-extra= is honored by both the main system and the
initrd. In the initrd, the mount point (and also source path if the mount is
bind mount) specified in systemd.mount-extra= is prefixed with
/sysroot/.
Example:
systemd.mount-extra=/dev/sda1:/mount-point:ext4:rw,noatime
Added in version 254.
.RE
.PP
systemd.swap-extra=WHAT[:OPTIONS],
rd.systemd.swap-extra=WHAT[:OPTIONS]
Specifies the swap unit. Takes the block device to be used as a swap device,
and optionally takes mount options followed by a colon (:). This option can
be specified multiple times. rd.systemd.swap-extra= is honored only
in the initrd, while systemd.swap-extra= is honored by both the main
system and the initrd.
Example:
systemd.swap-extra=/dev/sda2:x-systemd.makefs
Added in version 254.
.RE
.SH "SYSTEM CREDENTIALS"
.PP fstab.extra
This credential may contain addition mounts to establish, in the same format
as fstab(5), with one mount per line. It is read in addition to
/etc/fstab.
Added in version 254.
.RE
.SH "SEE ALSO"
.PP systemd(1), fstab(5), systemd.mount(5),
systemd.swap(5), systemd-cryptsetup-generator(8),
systemd-gpt-auto-generator(8), kernel-command-line(7),
Known Environment Variables[1]
NOTES
- 1.
- Known Environment Variables
| systemd 262.2 |