/proc/mounts "stuff"

/proc/mounts "stuff"

[Richard B. Johnson]

Linux version 2.2.24 (actually since pivot-root), have a
problem with what's in /proc/mounts vs. what's written
to /etc/mtab when mounting file-systems.

/etc/mtab

/dev/sda1 / ext2 rw 0 0
none /proc proc rw 0 0
none /dev/pts devpts rw,gid=5,mode=620 0 0
none /dev/shm tmpfs rw 0 0
/dev/sdb1 /usr/src ext2 rw 0 0

/proc/mounts

rootfs / rootfs rw 0 0
/dev/root / ext2 rw 0 0
/proc /proc proc rw 0 0
none /dev/pts devpts rw 0 0
none /dev/shm tmpfs rw 0 0
/dev/sdb1 /usr/src ext2 rw 0 0

/etc/issue

Red Hat Linux release 8.0 (Psyche)
Kernel 2.4.24 on a i586

On that system /dev/root doesn't even exist!
Neither does rootfs in any accessible way. Therefore,
the shutdown routine(s) that read /proc/mounts will
fail, leaving improperly dismounted volumes.  Basically,
if I execute `init 0` from the console, everything's
fine, but executing 'reboot' from a network connection
will result in a long fsucking startup.

I think the two unusable entries should not show in
/proc/mounts,
	rootfs / rootfs rw 0 0
	/dev/root / ext2 rw 0 0
That would fix the problem because there is no way to
umount either of them. Try it, `umount rootfs` returns
ENOENT as does `umount /dev/root'`.

Cheers,
Dick Johnson
Penguin : Linux version 2.4.24 on an i686 machine (797.90 BogoMips).
            Note 96.31% of all statistics are fiction.

Re: /proc/mounts "stuff"

[Chris Meadors]

On Tue, 2004-02-24 at 16:34, Richard B. Johnson wrote:
> Linux version 2.2.24 (actually since pivot-root), have a
> problem with what's in /proc/mounts vs. what's written
> to /etc/mtab when mounting file-systems.

[file contents snipped]

> On that system /dev/root doesn't even exist!
> Neither does rootfs in any accessible way. Therefore,
> the shutdown routine(s) that read /proc/mounts will
> fail, leaving improperly dismounted volumes.  Basically,
> if I execute `init 0` from the console, everything's
> fine, but executing 'reboot' from a network connection
> will result in a long fsucking startup.
> 
> I think the two unusable entries should not show in
> /proc/mounts,
> 	rootfs / rootfs rw 0 0
> 	/dev/root / ext2 rw 0 0
> That would fix the problem because there is no way to
> umount either of them. Try it, `umount rootfs` returns
> ENOENT as does `umount /dev/root'`.

I have been considering making this same post for a while.

I do have a /dev/root (a symlink to my actual root device), and it is no
better.  At shutdown/reboot time rootfs is still tried to be umounted
and fails leaving me with a dirty root at the next boot.


-- 
Chris

Re: /proc/mounts "stuff"

[Andreas Schwab]

"Richard B. Johnson" <root@chaos.analogic.com> writes:

> I think the two unusable entries should not show in
> /proc/mounts,
> 	rootfs / rootfs rw 0 0
> 	/dev/root / ext2 rw 0 0
> That would fix the problem because there is no way to
> umount either of them. Try it, `umount rootfs` returns
> ENOENT as does `umount /dev/root'`.

Since rootfs is a nodev filesystem the first column is an arbitrary
string, just like proc or devpts mounts.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux AG, Maxfeldstraße 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: /proc/mounts "stuff"

[Chris Friesen]

Richard B. Johnson wrote:
> Linux version 2.2.24 (actually since pivot-root), have a
> problem with what's in /proc/mounts vs. what's written
> to /etc/mtab when mounting file-systems.
> 
> /etc/mtab
> 
> /dev/sda1 / ext2 rw 0 0
> none /proc proc rw 0 0
> none /dev/pts devpts rw,gid=5,mode=620 0 0
> none /dev/shm tmpfs rw 0 0
> /dev/sdb1 /usr/src ext2 rw 0 0
> 
> /proc/mounts
> 
> rootfs / rootfs rw 0 0
> /dev/root / ext2 rw 0 0

The shutdown scripts on my system seem to be compensating for this. 
However, I'm hitting another problem where I do a pivot_root to a tmpfs 
filesystem and the shutdown scripts no longer know how to deal with it 
and try to unmount the real root filesystem from under themselves, 
causing all kinds of problems.

Chris

-- 
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