[lxc-devel] startup scripts for lxc containers?

[Michael Holzt]

> Oh, I thought init calls exit after it killed all children.

No it does not.

I was thinking about the problem the other day as well. I think some of it
is already covered by the work of Dietmar. I will describe my ideas in full
anyway:

1. lxc-start opens a pipe.

2. As the first process in the container a daemon e.g. lxc-ctld is launched
   which becomes pid 1. It will fork so that it will become pid 2 also and
   then in pid 1 a exec to the init binary is done so that init will be pid 
   1 as it expects. This process keeps one end of the pipe.

3. Now how to detect shutdown or reboot, i had two ideas.

   One is to modify /etc/init.d/halt and /etc/init.d/reboot to send a
   signal to lxc-ctld. Two different signals, one for halt, one for 
   reboot.

   Other idea is to just have init-ctl sit there. When it receives sigterm
   - emitted by init upon shutdown/reboot - it will determine runlevel
   (0 or 6) and thus know if it is reboot or halt.

   lxc-ctld will signal this to lxc-start through the pipe so that
   lxc-start now knows what action to take.

   lxc-ctld will not exit on sigterm but wait to be killed through sigkill
   by init.

4. lxc-start which knows that shutdown or reboot is in progress until
   lxc-ctld process is no longer in the process table and then kills
   the init in the container.

Problems: We know the "outer" pid of the init in the container but not
of lxc-ctld. Maybe change argv[0] to make it findable.

Comments?



Regards
Michael

-- 
It's an insane world, but i'm proud to be a part of it. -- Bill Hicks