Incorrect VFS Data For Non-Root Mountpoint

[sirtech]

We recently rolled out a new KVM virtual server guest with Ubuntu 12.04 that required a secondary block device. The primary is mounted on /, and all VFS results for this are fine. The secondary is mounted on /opt/k/mailserver/store but Zabbix refuses to recognize that it exists. I'm not sure if this is because I'm doing something wrong or if it's something that requires a 'workaround' because of the odd mount point.

This is Zabbix server version 2.0.3 and agent version 1.8.11-1.

On the Zabbix host:

[admin1@christine ~]$ zabbix_get -s 172.16.1.18 -k "vfs.fs.size[/opt/k/mailserver/store,pfree]"
ZBX_NOTSUPPORTED
[admin1@christine ~]$ zabbix_get -s 172.16.1.18 -k "vfs.fs.size[/,pfree]"
73.904349
[admin1@christine ~]$

On the guest itself:

Filesystem      Size  Used Avail Use% Mounted on
/dev/vda1       9.3G  2.4G  6.6G  27% /
udev            994M  4.0K  994M   1% /dev
tmpfs           401M  292K  401M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none           1002M     0 1002M   0% /run/shm
/dev/vdb1       150G  8.9G  134G   7% /opt/k/mailserver/store

[sirtech]

I managed to fix this when I went to write a custom plugin to obtain the data. What was happening is that Zabbix on Ubuntu will by default run as user 'zabbix' and this user did not have permission to access the mount point. Apparently the 'df' command requires access to the mount point in order to return details on the filesystem. Fixed the permissions and it all started working fine.