Citrix VDA Setup: What does “Create a master image” actually do?

Written by Jacques Bensimon:

What is MCS DOING?

Ever wonder how selecting the below “Create a Master Image” option during VDA setup actually changes the installation?


Well, I did wonder, and all I could find on the subject was a statement in a Citrix doc on VDA installation:  “The option you choose affects which Citrix provisioning tools are installed automatically (if any)”.  Ah, so selecting this MCS/PVS option installs some special “provisioning tools” as part of the VDA to aid in the eventual deployment process.  But what exactly?

To find out, I (of course) used my tool of choice Total Uninstall on a test VM to get a report of what changes between the following two points in time: (1) the VDA has been installed without the “master image” option, and (2) the VDA has been uninstalled then re-installed with the option.  The net difference, system noise aside, should be those wonderful additional “provisioning tools” … and it turns out that “they” apparently consist of exactly this one Registry value changing from 0 to 1:

Key:  HKLM\SOFTWARE\Citrix\Configuration
Value: (REG_DWORD) MasterImage

Unless Citrix is just taking a survey here, I can only assume that this setting changes something in the behavior of some of the VDA services during startup – maybe, for example, it’s what causes the VDA to execute what’s on the “instructions disk” during the MCS image preparation process described in this earlier post?  I’ll gladly entertain a more authoritative explanation or, barring that, some superior speculation.  Just leave it in the comments below.