There are times when you would want to provide an option or prompt the user to select a Deployment Share during an MDT Deployment, it quite simple to get it working with the help of Extra Directory.
See https://deploymentmechanic.wordpress.com/2015/10/31/add-extra-directory-to-winpe-x86-x64-in-mdt/ for more information about how to add Extra Directory. You would need to perform the following steps on any one of your deployment share and ensure that you generate WinPE ISO from the same deployment share.
Create an XML file and specify the various deployment servers/shares. You could copy the below sample content into Notepad and save it as LocationServer.xml. You would need to update friendlyname and UNCPath as per your infrastructure/deployment share.
<?xml version=”1.0″ encoding=”utf-8″ ?>
<friendlyname>Deployment LAB Share</friendlyname>
<friendlyname>Deployment Mechanic Lab Share</friendlyname>
Next create a folder called “Deploy” under the root of Extra Directory, in my case under the x86 and x64 folder.
Create another folder called “Control” under “Deploy” folder and Copy LocationServer.xml you created into the “Control” folder.
Next Launch Deployment Workbench, Open Properties of your Deployment Share where you have made required configuration to add the Extra Directory and Click on Rules Tab and Click on the Edit Bootstrap.ini button at the bottom.
Modify the Bootstrap.ini file to NOT include any DeployRoot value, you could either delete the line or comment the line by putting a semi-colon in front of the specific value in this case DeployRoot. We would need to do this cause the LocationServer.xml feature dynamically sets the value. Save and close Bootstrap.ini. Click OK on the Properties Windows.
Note : When you use the LocationServer.xml feature, By default the logic in this feature discards any credentials provided in bootstrap.ini
Next right click on the deployment share and click on update deployment share and completely regenerate the Boot Images and click Finish when done.
Boot off the new WinPE and you should see the LocationServer.xml feature in action.