Application Jail Shutdown Problem

[James Gritton]

On 2019-04-30 12:03, squiggly foo wrote:
> Hi All,
> 
> I use the mount.fstab parameter to mount a number of file systems
> before starting a jail which works without any problem.  However since
> it is an application jail, there are no other processes running inside
> the jail other than the one application.  As soon as that application
> terminates the jail is removed by the host.
> 
> This is actually my preferred behavior; I want the jail to be removed
> when the process inside of it terminates.  But the problem is that the
> mount points are not unmounted after the jail is removed that way.
> The only way I can get the jails to unmount is if I do a "jail -r
> jailname" which is what I want to avoid as I would not do that while
> the process inside the jail is still running.
> 
> 
> Does anyone know of a way for the jails to umount the mount points in
> its fstab file when the only process inside the jail exits?

No easy way.  Those filesystems have to be unmounted by somebody; the
jail can't do it because it doesn't have the permission (because it 
didn't
mount them).  So some process needs to be watching to see when the jail
goes away.  That would be some kind of watcher that wakes up 
occasionally
and sees if the jail is still there.  It might be nice to have some 
kqueue
support for jails.

- Jamie