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Re: trying to umount a chroot /dev



Ross Boylan wrote:
> I setup a chroot on a snapshot.  Part of the setup was
> mount --rbind /dev /mnt/chrtest/dev

Why did you choose "rbind" over "bind".  Just curious.  My reply is
the one I would give if you had used bind.  I have never used rbind.
The result may be wrong for rbind.  But it would be right for bind.

> I have exited the chroot and, I believe, ended the processes I started.
> umount /mnt/chrtest/dev
> gives umount: /mnt/chrtest/dev: device is busy
> 
> How can I get this to work?

Unmount that path.  Look at /proc/mounts for the path to anything
mounted in that directory tree and unmount it.  You will see something
like this bind mount.

  udev /srv/chroot/sid/dev devtmpfs rw,relatime,size=10240k,nr_inodes=493001,mode=755 0 0

In which case the umount command would be:

  # umount /srv/chroot/sid/dev

> After reviewing the output of mount I umounted the mounts below /dev,
> which seems to be the main advice on the net for undoing rbinds.

I think instead of unmounting below /dev you needed to unmount below
/mnt/chartest/dev instead.

If you really get stuck then rebooting should restore things to a sane
state since those mounts will not exist after a reboot.  But you
should be able to recover without rebooting.

Bob

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