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.