Re: [gentoo-user] How to unmount bind-mounted /dev?

[Alex Schuster]

Mick writes:

> On Sunday 01 May 2011 00:48:38 Alex Schuster wrote:

> > The lazy unmount was Thomas' hint already and worked, the partition is
> > no longer mounted. But I cannot fsck it, it is still in use. cryptsetup
> > luksClose works neither.
> > It's no big trouble, but still I'm curious why this is.

> Asking the obvious:  could this message be there because this partition
> is still mounted?

I grepped /proc/mounts for it and saw no references. I'm pretty sure I did 
not overlook something. And it's already the second time I tried this, one 
month ago the same had happened, but I did not care about it then.

> Did you check that this partition has been unmounted
> from all mount points, both original mount point and bind-mount?

The partition only has one mount point, but others were mounted inside it:

/dev/mapper/32 on /32             type ext3 (rw,noatime)
/dev           on /32/dev         type none (rw,bind)
/proc          on /32/proc        type none (rw,bind)
/home          on /32/home        type none (rw,bind,noatime)
/var/portage   on /32/var/portage type none (rw,bind,noatime)

/var/portage has another file system inside for the portage tree. When I 
want to unmount /32/var/portage, I have to unmount /32/var/portage/tree 
first. All except /32/dev could be unmounted, for /32/dev I needed the -l 
option to mount. Then /32 itself could be unmounted. But things like fsck or 
'cryptsetup remove' failed, /dev/mapper/32 was in use.

Then I rebooted, but I had forgotten to save my changes to fstab, so all 
those things were again mounted. I tried again anyway, and this time there 
was no problem. I had to use umount -l for /32/dev again, and this time also 
for /32/proc (that was not necessary the last time), but after unmounting 
/32, I could fsck its partition and shrink it.

I have no idea why it did not work the last times I tried. I'll try to 
reproduce this from time to time, maybe after some more uptime and work on 
this partition it will happen again.

	Wonko