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

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

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

       /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.