NGT Series | Post-thaw and Pre-freeze Scripts

  • 30 October 2019
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Getting the following error “VSS Scripts Not Installed” in your Nutanix environment with the description “VSS software or pre_freeze/post_thaw Scripts Not Installed”.

Confused about VSS and the above-mentioned scripts?

Let us help you understand the use of VSS for a snapshot!

When you are enabling the Nutanix Guest tool, the following features VSS and Application consistent snapshot is enabled by default.

Nutanix native in-guest VmQuiesced Snapshot Service (VSS) agent is used to take application-consistent snapshots for all the VMs that support VSS. This mechanism takes application-consistent snapshots without any VM stuns (temporary unresponsive VMs) and also enables third-party backup providers like CommVault and Rubrik to take application-consistent snapshots on the Nutanix platform in a hypervisor-agnostic manner.


What’s the use of pre_freeze/post_thaw then?

Within a Windows VM, NGT will use the Microsoft VSS writer built into the OS to quiesce the VM to take the app consistent snapshot. Linux does not have these built-in tools so a pre and post-thaw script must be installed to correctly quiesce the OS for the app consistency. If you do not install these scripts expected behaviour is to have crash-consistent snapshots versus application consistent.


Want to know more about the scripts?

Pre-Freeze|Post-thaw Script 

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