Linux run script automatically after boot

Question

I want to start a script, which set the system time automatically after booting. I wrote the command date -s "12/31/12 23:59" in rc.d/rc.local. That didn't work. How to solve that?

Answer 1

You are probably running ntp and it is setting the system time. You can try removing ntpd from startup at boot and you're system time should be 12/31/12 23:59.

Answer 2

If you are developing for an embedded target, you most likely are using BusyBox as your shell. If you read the BusyBox command documentation you will see this for the date command:

Recognized TIME formats:

       hh:mm[:ss]
       [YYYY.]MM.DD-hh:mm[:ss]
       YYYY-MM-DD hh:mm[:ss]
       [[[[[YY]YY]MM]DD]hh]mm[.ss]

So you have to change the date/time format you use in the command to one of the recognized.

Answer 3

If your system is running a version of cron that supports it (specifically Vixie cron), you can use @reboot in a cron job.

This is one of 8 special strings that it supports.

Quoting the crontab(5) man page (from my Ubuntu 12.04 system):

Instead of the first five fields, one of eight special strings may appear:

string         meaning
------         -------
@reboot        Run once, at startup.
@yearly        Run once a year, "0 0 1 1 *".
@annually      (same as @yearly)
@monthly       Run once a month, "0 0 1 * *".
@weekly        Run once a week, "0 0 * * 0".
@daily         Run once a day, "0 0 * * *".
@midnight      (same as @daily)
@hourly        Run once an hour, "0 * * * *".

Please note that startup, as far as @reboot is concerned, is the time when the cron(8) daemon startup. In particular, it may be before some system daemons, or other facilities, were startup. This is due to the boot order sequence of the machine.

This is far from being the only way to run something at boot time, but it's an alternative.