Pre-Freeze and Post-Thaw Scripts

If you back up or replicate VMs running applications that do not support Microsoft VSS, you can instruct Veeam Backup & Replication to run custom scripts for VMs. For example, the pre-freeze script may quiesce the file system and application data on the VM guest OS to bring the VM to a consistent state before Veeam Backup & Replication triggers a VM checkpoint. After the VM checkpoint is created, the post-thaw script may bring the VM and applications to their initial state.

You can use pre-freeze and post-thaw scripts for the following types of jobs:

  • Backup job
  • Replication job

Scripts must be created beforehand. You must specify paths to them in the job settings. Script execution settings can be configured per VM or per container, depending on the objects included in the job.

When the job starts, Veeam Backup & Replication uploads scripts to the VM guest OS and executes them under the account specified in the Guest OS credentials section of the job settings.

  • Scripts for Microsoft Windows VMs are uploaded to \\<vmname>\admin$ over the network. Scripts are executed from the C:\Windows directory.
  • Scripts for Linux VMs are uploaded over SSH or PowerShell Direct if the SSH connection fails. Scripts are executed from the /home/<username> directory of a user that you have specified in Guest OS credentials.

PowerShell Direct is used for VMs that reside on Microsoft Hyper-V Server 2016 or later and run Microsoft Windows 10 or Microsoft Windows Server 2016 or later. Veeam Backup & Replication requires Microsoft PowerShell 2.0 or later to work over PowerShell Direct.

The script is considered to be executed successfully if "0" is returned.

The default time period for script execution is 10 minutes. If the script fails to execute before the timeout expires, Veeam Backup & Replication displays an error message in the job session and error or warning messages issued during script execution.

Pre-Freeze and Post-Thaw Scripts 


Supported Script Formats

Pre-freeze and post-thaw scripts can be used for Microsoft Windows and Linux VMs.

Limitations for Pre-Freeze and Post-Thaw Scripts

Veeam Backup & Replication has the following limitations for pre-freeze and post-thaw scripts:

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