NAME

       fake-hwclock - Control fake hardware clock

SYNOPSIS

       fake-hwclock [ command ] [ force ]

BACKGROUND

       Many  embedded  Linux  systems  do  not have a functional hardware clock. Either they simply don't have a
       hardware clock at all or they have a hardware clock but it is not usable (e.g. because Linux doesn't know
       how to use it or because no battery is present).

       This can lead to time moving backwards to some default value (often 1970) when the  system  is  rebooted.
       Since  lots  of  software  assumes  that time only moves forward this is a bad thing. NTP can (and should
       where practical) be used to sync with an external timeserver but it is not available early  in  the  boot
       process and may be unavailable for other reasons.

       The  design  expectation  of  fake-hwclock is that it will be run very late at shutdown and very early at
       boot. This will ensure that fsck has a vaguely sensible idea of system time at boot  and  won't  complain
       that  the  last-modified  time  in the filesystem is not hugely in the past or future. Some users may not
       worry about this too use case, in which case it is possible to modify the init  system  configuration  to
       move things earlier/later as appropriate.

DESCRIPTION

       fake-hwclock  sets  and queries a fake "hardware clock" which stores the time in a file. This program may
       be run by the system administrator directly but is typically run by init (to load the time on startup and
       save it on shutdown) and cron (to save the time hourly).

       If no command is given then fake-hwclock acts as if the save command was used.

COMMANDS

       save   Save the time to the file. As a sanity check, fake-hwclock will not move the saved clock backwards
              to a time/date earlier than its own release date. Use "force" to over-ride this check.

       load   Load the time from the file. If force  is  specified  fake-hwclock  will  move  the  clock  either
              backwards or forwards. Otherwise it will only move it forwards.

FILES

       /etc/fake-hwclock.data
              The file used to store the time

       /etc/init.d/fake-hwclock
              The init script used to run fake-hwclock on startup and shutdown

       /usr/lib/systemd/system/fake-hwclock-load.service
              systemd service used to run fake-hwclock on startup

       /usr/lib/systemd/system/fake-hwclock-save.service
              systemd service used to run fake-hwclock on shutdown

       /usr/lib/systemd/system/fake-hwclock-save.timer
              systemd timer used to save the time hourly

       /etc/default/fake-hwclock
              Settings file for the init script.

       /etc/cron.hourly/fake-hwclock
              Cron job used to save the time hourly

ENVIRONMENT VARIABLES

       FILE   set the file used by fake-hwclock

RETURN VALUES

       1 is returned for invalid commands. 0 is returned in all other cases.

BUGS

       This  approach  can only provide a crude approximation of what a real hardware clock provides. Use of NTP
       or another method to keep the time in sync is strongly advised.

Debian                                            14 July 2024                                   FAKE-HWCLOCK(8)