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Why do SSH Disk Free and SNMP Linux Disk Free show different values for my target Linux system?



I installed the SNMP Disk Check sensor and it seems to work, but it returns values that are significantly different from what they really are. The SSH Disk check works fine, so it must be something with SNMP. Any thoughts as to what could be the problem?

available disk-free free prtg sensors snmp space ssh values

Created on Nov 5, 2012 10:34:12 AM by  Daniel Zobel [Product Manager]

Last change on May 6, 2019 11:17:25 AM by  Maike Guba [Paessler Support] (2,404) 2 1

1 Reply

Accepted Answer



This article applies as of PRTG 22

Disk free measurements via SNMP vs. SSH

Both the SSH Disk Free and SNMP Linux Disk Free sensors report correct values with their individual method of measurement:

  • The SSH Disk Free sensor uses the df command and returns the free space of the volume, minus a reserve defined for this volume. As a result, it shows the disk space that is actually available for use.

Note: The size of the reserved disk space can be defined with tune2fs.

  • The SNMP Linux Disk free sensor returns the free space (this means all disk space that is not yet used). However, not all of this space may be available for use, as part of it can be reserved.


Created on Nov 5, 2012 10:58:26 AM by  Daniel Zobel [Product Manager]

Last change on Jan 3, 2023 8:07:09 AM by  Brandy Greger [Paessler Support]

Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.