Root filesystem on ext2

Bryan Kadzban bryan at
Mon Oct 9 02:13:14 UTC 2006

Bodo Thiesen wrote:
> Solutions:
> a) Make the ext3 file system driver a part of the static kernel
> b) Don't unmount the root file system before rebooting
> c) Change the file system of the initrd to ANYTHING else than ext2
>    AND make ext2 a module as like ext3. Them make sure to modprobe
>    ext3 BEFORE ext2.

d) Change your initramfs to manually mount the root filesystem.  You
will be able to completely specify what you want mount to do, including
use a different FS than it normally would.

(Er, wait, you still use an initrd?  I suppose that doesn't really
matter, but initramfs is newer.)

> Some peoble even deleted /etc/mtab already and replaced it by a
> symlink to /proc/mount. Other peoble told that to be a problem, I
> don't see the point, but just to warn you ;). For me, it worked fine.

You must not be using any mount options that require keeping state
between mount and umount, then.  That's not the case in general.

One such option is "user" -- with "user", any user can mount the FS, but
only that same user (or root) is allowed to umount it.  To enforce this,
mount has to keep track of which user did the mount -- it does so in
/etc/mtab.  The kernel doesn't care (this restriction is enforced by the
setuid-root mount and umount programs, not the kernel), so that
information does not appear in /proc/mounts at all.

If you have a "user" FS in fstab, then I'd be willing to bet that any
user can mount it, and any other user can umount it.  If you want to try
it in your symlink setup, mount one of them as root, then see if you can
umount it as a user.  I can't when mtab is not a symlink; this is
correct behavior.
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