From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <ec141718913bbac01b1436b2131af4b3@quanstro.net>
From: erik quanstrom <quanstro@quanstro.net>
Date: Wed, 24 Jun 2009 07:41:42 -0400
To: 9fans@9fans.net
In-Reply-To: <2c7a0fb7-0aba-4337-8120-60cfc1192a5c@x5g2000yqk.googlegroups.com>
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Subject: Re: [9fans] Unmount of /mnt directory
Topicbox-Message-UUID: 0de1f09c-ead5-11e9-9d60-3106f5b1d025

> it seems I still do not fully understand namespaces.
> But this sequence seems strange to me:
>
> cdfs -d /dev/sdD0
> unmount /mnt/cd
>
> ...everything is OK.
>
> cdfs -d /dev/sdD0
> unmount /mnt
>
> ...I unmounted wrong directory...
>
> cdfs -d /dev/sdD0
> cdfs: openscsi '/dev/sdD0': '/dev/sdD0/raw' device or object already
> in use
>
> ...this situation is persistent.
>
> What happened in the system when I unmounted /mnt directory?

on my system /mnt is constructed like this

	chula# ns | grep '/mnt $'
	bind -c /root/mnt /mnt
	mount -a '#s/factotum' /mnt

if i unmount /mnt i get

	chula# unmount /mnt
	chula#  '/mnt $'

it might be surprising that, e.g.,
	mount -c '#D/ssl/2/data' /mnt/term
is not unmounted, but the mntpt isn't /mnt,
it's /mnt/term.  things below /mnt are not
accessable because we must walk from the
root.

with this knowledge, one can reconstruct
the former namespace and unmount /mnt/cd.

	chula# bind -c /root/mnt /mnt
	chula# mount -a '#s/factotum' /mnt
	chula# unmount /mnt/cd

alternatevely, "slay cdfs | rc" would work,
if you didn't care about that ns being screwy.

- erik