GNU bug report logs - #8208
Possible bug for df

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Jesse Molina <jesse <at> opendreams.net>
To: bug-coreutils <at> gnu.org
Subject: Possible bug for df
Date: Wed, 09 Mar 2011 02:36:31 -0700

The "df" tool will mismatch mounted devices when a specific device 
parameter is specified.

Here's some console output from running df;

[/var/log]
shara <at> sorrows-->df -h /dev/md5
Filesystem            Size  Used Avail Use% Mounted on
/dev/md5              2.3T  1.7T  534G  76% /mnt/backup/bak5
[/var/log]
shara <at> sorrows-->df -h /dev/md5
Filesystem            Size  Used Avail Use% Mounted on
udev                  881M  372K  880M   1% /dev



In the second invocation, the /dev/md5 device had been dismounted, but 
the /dev filesystem is now being matched, when it should not be.

Expected behavior is to get non-zero exit code and print nothing, and/or 
an error on stderr that the device is not found.

Note that this was to be used in a script.  I tried with the -P flag, 
and the behavior is the same, in that the wrong mount is matched.



shara <at> sorrows-->df --version
df (GNU coreutils) 8.5
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
<http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Torbjorn Granlund, David MacKenzie, and Paul Eggert.


Also FYI

shara <at> sorrows-->df -v
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/sor--vg1-root
                       8256952   3884136   4288932  48% /
tmpfs                   906132         4    906128   1% /lib/init/rw
udev                    901260       372    900888   1% /dev
tmpfs                   906132         4    906128   1% /dev/shm
/dev/md0                241036    108803    107344  51% /boot
/dev/mapper/sor--vg1-tmp
                       2064208     71112   1888240   4% /tmp
/dev/mapper/sor--vg1-var
                     1906616172 621163644 1266103904  33% /var
/dev/mapper/sor--vg1-var--log
                       4128448   2038268   2090180  50% /var/log



No reply needed.  Sorry if this is duplicate or expected behavior.



-- 
# Jesse Molina
# Mail = jesse <at> opendreams.net
# Page = page-jesse <at> opendreams.net
# Cell = 1.602.323.7608
# Web  = http://www.opendreams.net/jesse/

Message #10 received at 8208-done <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Jesse Molina <jesse <at> opendreams.net>
Cc: 8208-done <at> debbugs.gnu.org
Subject: Re: bug#8208: Possible bug for df
Date: Wed, 09 Mar 2011 16:20:54 +0000

On 09/03/11 09:36, Jesse Molina wrote:
> 
> The "df" tool will mismatch mounted devices when a specific device
> parameter is specified.
> 
> Here's some console output from running df;
> 
> [/var/log]
> shara <at> sorrows-->df -h /dev/md5
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/md5              2.3T  1.7T  534G  76% /mnt/backup/bak5
> [/var/log]
> shara <at> sorrows-->df -h /dev/md5
> Filesystem            Size  Used Avail Use% Mounted on
> udev                  881M  372K  880M   1% /dev
> 
> 
> 
> In the second invocation, the /dev/md5 device had been dismounted, but
> the /dev filesystem is now being matched, when it should not be.
> 
> Expected behavior is to get non-zero exit code and print nothing, and/or
> an error on stderr that the device is not found.
> 
> Note that this was to be used in a script.  I tried with the -P flag,
> and the behavior is the same, in that the wrong mount is matched.

This is expected behavior. If the passed file is not a mount point itself,
df will go and find it's mount point, and report for that device.

If you want to enforce that the passed device node is mounted
then I suggest you ensure that the file system is the same as passed, like:

dev=/dev/md5
df_dev=$(df -P $dev | sed -n '2s/\([^ ]*\).*/\1/p')
test "$dev" = "$df_dev" || { echo "$dev not mounted" >&2; exit 1; }

cheers,
Pádraig.

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