linux-kernel - Re: How do I make a clean mount namespace?

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Message-ID: <CAFLxGvyn4q3VfRrAcjO6meZ1UJwRZ5-yeaMExGX5ogtnuAkPBQ@mail.gmail.com>
Date:	Wed, 23 Apr 2014 22:01:27 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: How do I make a clean mount namespace?

On Wed, Apr 23, 2014 at 12:12 AM, Andy Lutomirski <luto@...capital.net> wrote:
> I want to set up a little container.  So I unshare the mount namespace
> and mount something somewhere (say /mnt) that I want to be my new
> root.  Now what?
>
> pivot_root("/mnt", "/mnt/garbage") seems to frequently return -EBUSY.
>
> mounting /mnt onto / using MS_MOVE seems to succeed, but / still
> points at the old root.
>
> Am I missing a clean way to do this?  I want a way to say "make this
> mountpoint be the root of the whole mount namespace and lazy-unmount
> everything outside it".  If there is no straightforward way to do
> that, can we add one?

I fear you have to read /proc/mounts and umount() everything in the
correct order.
If you find a better way, please tell. :-)

-- 
Thanks,
//richard
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