timedatectl(1)

Common pager commands like less(1), in addition to "paging", i.e. scrolling through the output, support opening of or writing to other files and running arbitrary shell commands. When commands are invoked with elevated privileges, for example under sudo(8) or pkexec(1), the pager becomes a security boundary. Care must be taken that only programs with strictly limited functionality are used as pagers, and unintended interactive features like opening or creation of new files or starting of subprocesses are not allowed. "Secure mode" for the pager may be enabled as described below, if the pager supports that (most pagers are not written in a way that takes this into consideration). It is recommended to either explicitly enable "secure mode" or to completely disable the pager using --no-pager or PAGER=cat when allowing untrusted users to execute commands with elevated privileges.

This option takes a boolean argument. When set to true, the "secure mode" of the pager is enabled. In "secure mode", LESSSECURE=1 will be set when invoking the pager, which instructs the pager to disable commands that open or create new files or start new subprocesses. Currently only less(1) is known to understand this variable and implement "secure mode".

When set to false, no limitation is placed on the pager. Setting SYSTEMD_PAGERSECURE=0 or not removing it from the inherited environment may allow the user to invoke arbitrary commands.

When $SYSTEMD_PAGERSECURE is not set, systemd tools attempt to automatically figure out if "secure mode" should be enabled and whether the pager supports it. "Secure mode" is enabled if the effective UID is not the same as the owner of the login session, see geteuid(2) and sd_pid_get_owner_uid(3), or when running under sudo(8) or similar tools ($SUDO_UID is set [1]). In those cases, SYSTEMD_PAGERSECURE=1 will be set and pagers which are not known to implement "secure mode" will not be used at all. Note that this autodetection only covers the most common mechanisms to elevate privileges and is intended as convenience. It is recommended to explicitly set $SYSTEMD_PAGERSECURE or disable the pager.

Note that if the $SYSTEMD_PAGER or $PAGER variables are to be honoured, other than to disable the pager, $SYSTEMD_PAGERSECURE must be set too.

.RE

.PP $SYSTEMD_COLORS

$ timedatectl


               Local time: Thu 2017-09-21 16:08:56 CEST


           Universal time: Thu 2017-09-21 14:08:56 UTC


                 RTC time: Thu 2017-09-21 14:08:56


                Time zone: Europe/Warsaw (CEST, +0200)
System clock synchronized: yes


              NTP service: active


          RTC in local TZ: no

$ timedatectl set-ntp true
==== AUTHENTICATING FOR org.freedesktop.timedate1.set-ntp ===
Authentication is required to control whether network time synchronization shall be enabled.
Authenticating as: user
Password: ********
==== AUTHENTICATION COMPLETE ===

$ systemctl status systemd-timesyncd.service
● systemd-timesyncd.service - Network Time Synchronization


   Loaded: loaded (/usr/lib/systemd/system/systemd-timesyncd.service; enabled)


   Active: active (running) since Mo 2015-03-30 14:20:38 CEST; 5s ago


     Docs: man:systemd-timesyncd.service(8)


 Main PID: 595 (systemd-timesyn)


   Status: "Using Time Server 216.239.38.15:123 (time4.google.com)."


   CGroup: /system.slice/systemd-timesyncd.service


           └─595 /usr/lib/systemd/systemd-timesyncd
...

$ timedatectl timesync-status


       Server: 216.239.38.15 (time4.google.com)
Poll interval: 1min 4s (min: 32s; max 34min 8s)


         Leap: normal


      Version: 4


      Stratum: 1


    Reference: GPS


    Precision: 1us (-20)
Root distance: 335us (max: 5s)


       Offset: +316us


        Delay: 349us


       Jitter: 0


 Packet count: 1


    Frequency: -8.802ppm