* Fwd: Bug#747948: mount: should warn user when potentially incorrect fstab order
[not found] <20140513100450.GA1083@europecamions-interactive.com>
@ 2014-05-13 12:59 ` Phillip Susi
2014-05-26 10:24 ` Karel Zak
0 siblings, 1 reply; 3+ messages in thread
From: Phillip Susi @ 2014-05-13 12:59 UTC (permalink / raw)
To: util-linux
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Forwarding this request from debian to get your thoughts.
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Package: mount
Version: 2.20.1-5.3
Severity: wishlist
Hello, there.
Firstly, tl;dr: mount should warn when interlocked mountpoints in fstab
aren't in the expected order.
I recently noticed what at first seemed a bug in mount management of
fstab, but, according to the french mailing list users, it's more a lack
of warning.
Here is the problem: currently, at start, filesystems referenced in
fstab are mounted following their order in fstab. The problem is, when
/etc/fstab contains config for two filesystems with interlocked
mountpoints, in my case /var/www and /var/www/cache, they are not
necessarily in the right order. In my example, because of limitations in
my hosting provider installer and my drive configuration, /var/www/cache
configuration was stored before /var/www's one. Because man mount did
not contained any warning regarding mountpoints order, I assumed this
was automagically managed at start; of course, it proved me wrong, as
you can see in the following command dump taken after a reboot:
david@Curunir:~$ df -h
Sys. fich. Taille Util. Dispo Uti% Monté sur
rootfs 54G 3,1G 49G 6% /
udev 10M 0 10M 0% /dev
tmpfs 13G 328K 13G 1% /run
/dev/md1 54G 3,1G 49G 6% /
tmpfs 5,0M 0 5,0M 0% /run/lock
tmpfs 35G 0 35G 0% /dev/shm
/dev/md3 20G 233M 19G 2% /var/log
/dev/md4 1,7T 852M 1,6T 1% /var/www/cache
/dev/md6 99G 188M 94G 1% /home
/dev/md7 1,7T 852M 1,6T 1% /var/www
tmpfs 32G 0 32G 0% /tmp
david@Curunir:~$ sudo su
[sudo] password for david:
root@Curunir:/home/david# umount /dev/md4
umount: /var/www/cache: not mounted
root@Curunir:/home/david# mount /dev/md4
root@Curunir:/home/david# df -h
Sys. fich. Taille Util. Dispo Uti% Monté sur
rootfs 54G 3,1G 49G 6% /
udev 10M 0 10M 0% /dev
tmpfs 13G 328K 13G 1% /run
/dev/md1 54G 3,1G 49G 6% /
tmpfs 5,0M 0 5,0M 0% /run/lock
tmpfs 35G 0 35G 0% /dev/shm
/dev/md3 20G 233M 19G 2% /var/log
/dev/md4 124G 188M 118G 1% /var/www/cache
/dev/md6 99G 188M 94G 1% /home
/dev/md7 1,7T 852M 1,6T 1% /var/www
tmpfs 32G 4,0K 32G 1% /tmp
/dev/md4 124G 188M 118G 1% /var/www/cache
As you can see, in this case, the mounting of /var/www/cache behaves
erratically when its configuration is placed before /var/www's one in
/etc/fstab. When I noticed this problem, I checked all system logs, but
none showed messages regarding the mountpoints order, so I suspected a
failed disk, but my hosting provider's checks did not show any problem,
no more than fsck -f. I almost reinstalled the system, but, at the last
moment, I thought of fstab and changed mountpoints order to place
/var/www before /var/www/cache, and, after a reboot, the problem was
solved.
I mailed yesterday the Debian french users mailing list about this
problem, which I thought of as a bug, but they explained me that, under
some conditions, this behaviour may prove helpful. Nevertheless,
I still think that mount should warn about this most likely unwanted
behaviour, both in its manpage and by logging warnings in dmesg or syslog,
in order to help users confronted to this problem. At first, I expected
mount to reject such a mountpoint order to avoid problems, but, if I'm
right, it should be a bit extreme and bother users who uses this
behaviour to their advantage.
So, I would like to request the addition in mount of a warning when it
tries to mount a filesystem whose mountpoint contains an already used
mountpoint in order to avoid confusion for filesystem administation.
This warning should be printed on stderr, if not in dmesg and syslog, to
allow the admin to correct mountpoints order in the most likely case the
current behaviour is not the expected one.
Thanks for reading.
Regards.
--
David Guyot
Administrateur système, réseau et télécommunications / Sysadmin
Europe Camions Interactive / Stockway
Moulin Collot
F-88500 Ambacourt
Tel: +33 (0)3 29 30 47 85
Fax : +33 (0)3 29 31 31 31
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