[Qemu-devel] stale pid files?

[Axel Kittenberger]

Hi list again, another suggestion.

I use the deamons pidfile feature to write pidfiles so I can controll 
the virtual machines with /etc/init.d/bla scripts, to e.g. auto spawn 
the guests when the server starts, auto/start/stop with runlevels and so 
on.. However I got following issue, the daemon wont start if there is a 
pidfile already (yes no problem for user to delete, but for auto 
spawning after unattended boot) . Since e.g. following situation: BANG! 
Powerout! .... System goes up when power is available again. The init 
scripts want to start the qemu/kvm deamons, but they refuse because 
these see their pidfiles already from pre-powerout..

I have seen other daemons somehow locking their pidfiles while running, 
and when killed -9ed, or poweroutes and they start again, they see their 
pid-file is unlocked, thus stale, and just overwrite it... only notifing 
you with a message they did so.

Kind Regards,
Axel