Re: /etc/mtab and per-process namespaces

[Michael Tokarev <mjt@tls.msk.ru>]

Christoph Hellwig wrote:
> I suspect not one cares about /etc/mtab.  It's a pretty horrible
> interface.  Use /proc/self/mounts if your care about the mount table
> for your current namespace, it's guranteed uptodate.

Well, it's uptodate, but it isn't the same as mtab.  Like:

   /tmp/test on /mnt/test type ext2 (rw,loop=/dev/loop/0)
(mtab), vs
   /dev/loop/0 /mnt/test ext2 rw 0 0

or:

  tmpfs on /dev type tmpfs (rw,size=10M,mode=0755)
vs
  tmpfs /dev tmpfs rw 0 0

ie, sometimes, mtab format is more useful.  Also, with the
above example with loop device, umount is able to delete the
loop device for loop-mounts.

Another funky example:

   losetup /dev/loop/0 /tmp/test
   cd /dev/loop
   mount 0 /mnt/test

now, mtab shows:

   /dev/loop/0 /mnt/test ext2 rw 0 0

while /proc/mounts shows

   0 /mnt/test ext2 rw 0 0

which is rather useless.

/mjt