Public bug reported:
Binary package hint: util-linux
mount ignores any options given for bind mounts and adds an incorrect line to
mtab.
there is (at least) one exception: the option ro (== read-only). it warns that
the bind mount is mounted read-write, if one tries to use that option together
with bind.
some examples of the current behavior (with comments):
~/bla# mkdir foo
~/bla# mkdir bar
~/bla# touch foo/test
~/bla# mount foo/ bar/ -obind,ro
mount: warning: bar/ seems to be mounted read-write.
# at least it says so
~/bla# rm bar/test
~/bla# ls bar/test
ls: cannot access bar/test: No such file or directory
# expected after that warning
~/bla# touch foo/test
~/bla# mount foo/ bar/ -obind,somebogusoption1
~/bla# mount foo/ bar/ -obind,somebogusoption2
~/bla# mount foo/ bar/ -obind,somebogusoption3
~/bla# mount
...
/root/bla/foo on /root/bla/bar type none (rw,bind)
/root/bla/foo on /root/bla/bar type none (rw,bind,somebogusoption1)
/root/bla/foo on /root/bla/bar type none (rw,bind,somebogusoption2)
/root/bla/foo on /root/bla/bar type none (rw,bind,somebogusoption3)
# mount adds bogus lines to mtab...
~/bla# ls bar/
test
# but at least it does mount
umount bar
mount
...
/root/bla/foo on /root/bla/bar type none (rw,bind)
/root/bla/foo on /root/bla/bar type none (rw,bind,somebogusoption1)
/root/bla/foo on /root/bla/bar type none (rw,bind,somebogusoption2)
# and umount only removes one (bogus) line per execution :)
the behavior is kinda documented in the manpage (well the bogus lines are
clearly a bug (two actually), but i don't care right now).
a workaround is to first bind mount and then use the remount option for setting
other options e.g.:
~/bla# mount foo/ bar/ -obind
~/bla# mount bar/ -oremount,ro
~/bla# rm bar/test
rm: cannot remove `bar/test': Read-only file system
the problem is... this does not work with fstab:
neither setting up one line with options bind,ro such as
/root/bla/foo /root/bla/bar none bind,ro
(this gives the same warning as above)
nor using two, one with the remount option:
/root/bla/foo /root/bla/bar none bind
/root/bla/foo /root/bla/bar none remount,ro
(this even fails silently to remount read-only!)
the warning was introduced by Karel Zak in november 2009. i read that debian
had a patch for correcting at least some of the issues above, but i could not
find anything.
one workaround for certain situations could be to use pam_mount.
this war reported/tested on ubuntu 10.10 with kernel 2.6.35-25 and mount
2.17.2-0ubuntu1.10.10.1.
** Affects: util-linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/712892
Title:
mount (silently) ignores options for bind mounts
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