VMware Backup Pre- and Post-Commands

SUMMARY

VMware Backup Pre- and Post-Commands are commonly used to run custom scripts for freezing and thawing VMs during a backup

ISSUE

Purpose

This article outlines the VMware-supported method for running custom commands before and after vProtect backs up a virtual machine.

Description

Pre- and Post-commands are most often used to quiesce an application that does not have its own VSS provider (if Windows) to ensure a consistent state before backup.   With VMware tools installed, VMware ESX 3.5 and later defines a specific location inside the VM where quiescing scripts should be placed, and if present they will be invoked before and after the backup runs.   The pre-command is known as the pre-freeze script, while the post-command is the post-thaw script.

Cause

Some applications may not back up in a consistent state with a normal VMware backup.

Resolution

To quiesce the application before a vProtect backup runs, a prerequisite is that VMware tools are installed in the VM.  Then, you need to create a pre-freeze and post-thaw script that will run before and after the backup runs.

For Windows VMs, please see this Knowledge Base article from VMware  that describes the directory location of the scripts per ESX/ESXi version and also provides more information about execution order if you want to quiesce multiple applications, format of the scripts, etc.

For Linux VMs, the scripts should be named

     /usr/sbin/pre-freeze-script

     /usr/sbin/post-thaw-script

 

Both must have 0755 permissions so that they are executable, and should be owned by root.

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