FAKE-HWCLOCK(8) System Manager's Manual FAKE-HWCLOCK(8)
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.
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.
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
/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 5 April 2012 FAKE-HWCLOCK(8)