The VMST is a patch management solution which can be used to update stopped or saved state VM’s on a Hyper-V or Hyper-V R2 host. And also VM Templates, offline VM’s and offline Virtual Hard Disks(VHD) stored in the VM Library of System Center 2012 Virtual Machine Manager (SCVMM). In order to achieve this, the tool applies updates to the VHD using so called Servicing Jobs.
Servicing Jobs, which use Windows PowerShell start the VM, update the VM and either shuts down the VM or brings the VM back into a saved state. Offline VHD’s are updated by mounting them to a running host and updating it using the Deployment Imaging Servicing and Management (DISM) tool.
VMST can leverage either the software update functionality of System Center 2012 Configuration Manager (SCCM) or Windows Server Update Services (WSUS) version 3.0 SP2 to achieve this.