[Bug 906293] Re: Get rid of /etc/mtab and store userspace options in /run

[Martin Pitt]

Subscribing Foundations team for comments/input, but assigning to myself
for now.

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https://bugs.launchpad.net/bugs/906293

Title:
  Get rid of /etc/mtab and store userspace options in /run

Status in “util-linux” package in Ubuntu:
  Triaged
Status in “util-linux” source package in q-series:
  Triaged

Bug description:
  /etc/mtab has always been a bit of a wart, as it's potentially broken
  to put information about mounted file system on a mountedfile system.
  It is out of date in rescue mode when / is read-only (but "mount"
  output won't tell you), and leads to bugs like bug 891688 or bug
  13131.

  The only reason why we still have it is that /proc/mounts is not able
  to store userspace-only extra options which e. g. udisks
  (uhelper=udisks), pm-utils (commit=XXX), or NFS use.

  These days there is a better option for this. Copying response from
  util-linux upstream Karel Zak:

    "When linked with libmount (--enable-libmount-mount) then the
  userspace options (and only the options) are maintained by library in
  userspace in /run/mount/utab. The mount, umount and findmnt are able
  to see these options from by libmount. It's also supported by the
  latest mount.nfs (as NFS requires some userspace stuff too)..

   See Fedora, we don't use mtab any more. (Well, some utils like df have problem to de-duplicate list of mounted filesystems, but all
   basic things works as expected.)"

  This is worth investigating for the Q cycle.

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