Rebooting jails

Dirk Engling erdgeist at
Mon Jul 24 17:45:08 UTC 2006


I'm currently looking for a standardized way to 'reboot' jails from 
within. 'shutdown' is a simple one, just issue 'kill -TERM -1' and you're 

Now, rebooting generally involves starting up the jail afterwards.

One way that works from a shell started via jexec would be to 'kill 
-TERM -1' all processes and execve into whatever is supposed to be the 
kickoff command, e.g. /bin/sh /etc/rc. However, doing this from a shell 
that has been run from sshd results in killing the sshd and thus the shell 
trying to restart the jail.

Another way would be to have a daemon waiting in the host system that is 
checking jids in /var/run/jail_*.id say all 5 Minutes and if pgrep returns 
anything than 0, the jail is being restarted (you may combine that with 
some conditions, say having a file '/.rebootme' under jail's root 

This approach is more a watchdog than a reboot mechanism, you would need 
to do unintuitive stuff like adding a line to crontab (where it would even 
run if no jails are active, which sucks). One could use an 'at +5m 
$prefix/bin/watchdog' in the script that starts the jail in the first 
place which calls itself the same way.

All this is annoying to track, a watchdog script sleeping in the 
background would more easily be visible in ps. And, waiting for the host 
system to finally rerun to jail may cost many boring admin-5min-periods.

Maybe someone can help me out with a cool idea.



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