Re: Using mount -o bind vs mount -o subvol=vol

[Marc MERLIN <marc@merlins.org>]

On Sun, May 04, 2014 at 09:07:55AM +0200, Brendan Hide wrote:
> On 2014/05/04 02:47 AM, Marc MERLIN wrote:
> >Is there any functional difference between
> >
> >mount -o subvol=usr /dev/sda1 /usr
> >and
> >mount /dev/sda1 /mnt/btrfs_pool
> >mount -o bind /mnt/btrfs_pool/usr /usr
> >
> >?
> >
> >Thanks,
> >Marc
> There are two "issues" with this.
> 1) There will be a *very* small performance penalty (negligible, really)

Oh, really, it's slower to mount the device directly? Not that I really
care, but that's unexpected.
 
> 2) Old snapshots and other supposedly-hidden subvolumes will be
> accessible under /mnt/btrfs_pool. This is a minor security concern
> (which of course may not concern you, depending on your use-case).
> There are a few similar minor security concerns - the
> recently-highlighted issue with old snapshots is the potential that
> old vulnerable binaries within a snapshot are still accessible
> and/or executable.

That's a fair point. I can of course make that mountpoint 0700, but it's
a valid concern in some cases (not for me though).

So thanks for confirming my understanding, it sounds like both are valid
and if you're already mounting the main pool like I am, that's the
easiest way.

Thanks,
Marc
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