fake-hwclock
Control fake hardware clock
root@kali:~# man fake-hwclock
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.
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 di-
rectly 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.service
systemd service 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 1 October 2014 FAKE-HWCLOCK(8)