Monit fails to monitor filesystem, says "'var' unable to read filesystem /dev/dm-12 state"

[Odin Kroeger]

Dear Monit-community,

after upgrading from Debian 5 to Debian 6, Monit fails to monitor my
'/var'-filesystem, which is located on a logical volume, it reports:

  'var' unable to read filesystem /dev/dm-12 state

* I am using Monit version 5.1.1, which comes with Debian 6 (sqeeze).
* /var is located on a logical volume at /dev/mapper/ister-var,
which is a symlink pointing to /dev/dm-12.

The relevant portion of my /etc/monit/monitrc reads as follows:

  check device var with path /dev/mapper/ister-var
          if space usage > 75% then alert
          if inode usage > 75% then alert


== Previous discussion on this mailing list ==

I have read
http://lists.nongnu.org/archive/html/monit-general/2010-05/msg00000.html
and none of the causes mentioned there seems to apply; to be precise:

* /var is mounted.
* We do not use SELinux.
* Our server is real, not virtual
(though it hosts virtual servers, using Xen).

monit -Iv does not seem to give any additional information compared to
the error message quoted above.


== Further Research ==

A similar monitoring rule is in effect for the root filesystem, which
does not reside on a logical, but a physical volume; this seems to work
out fine. The relevant portion of /etc/monit/monitrc reads:

  check device rootfs with path /dev/cciss/c0d0p2
          if space usage > 75% then alert
          if inode usage > 75% then alert


Additional testing with Python suggests that the statvfs() call succeeds
for /var, that is, the following script reports no errors:

  import os
  print os.statvfs('/var')

This prints:

  posix.statvfs_result(f_bsize=4096, f_frsize=4096,
  f_blocks=2064238, f_bfree=1698423, f_bavail=1593566, f_files=1048576,
  f_ffree=1039052, f_favail=1039052, f_flag=4102, f_namemax=255)


== Additional Details of our Setup ==

/etc/mtab - at the time of the error messages - reads:

  /dev/cciss/c0d0p2 / ext3 rw,errors=remount-ro 0 0
  tmpfs /lib/init/rw tmpfs rw,nosuid,mode=0755,size=32M 0 0
  proc /proc proc rw,noexec,nosuid,nodev 0 0
  sysfs /sys sysfs rw,noexec,nosuid,nodev 0 0
  udev /dev tmpfs rw,mode=0755 0 0
  tmpfs /dev/shm tmpfs rw,nosuid,nodev,size=32M 0 0
  devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=620 0 0
  /dev/cciss/c0d0p1 /boot ext3 rw 0 0
  /dev/mapper/ister-home /home ext3 rw,nosuid,nodev,user_xattr 0 0
  /dev/mapper/ister-hp /hp ext3 rw,nodev 0 0
  /dev/mapper/ister-opt /opt ext3 rw,nodev 0 0
  /dev/mapper/ister-tmp /tmp ext3
    rw,nosuid,nodev,usrquota,grpquota,user_xattr 0 0
  /dev/mapper/ister-usr /usr ext3 rw,nodev 0 0
  /dev/mapper/ister-usr--local /usr/local ext3 rw,nodev 0 0
  /dev/mapper/ister-var /var ext3
    rw,nosuid,nodev,usrquota,grpquota,user_xattr 0 0
  xenfs /proc/xen xenfs rw 0 0

Please find our complete /etc/monitrc (monitrc) and the complete output
of monit -Iv (monit.log) attached.


Versions:

Linux version 2.6.32-5-xen-amd64 (Debian 2.6.32-30)
(address@hidden) (gcc version 4.3.5 (Debian 4.3.5-4) ) #1 SMP Wed
Jan 12 05:46:49 UTC 2011

LVM version:     2.02.66(2) (2010-05-20)
Library version: 1.02.48 (2010-05-20)
Driver version:  4.15.0


Thanks a lot for your help,

Odin Kroeger

monit.log
Description: Text document

monitrc
Description: Text document