If you want to debug an MSBuild script from without Visual Studio, you need to use the /debug command line option.
The trick is that this option is not normally available; you need to set a registry key to enable it.
Enable the MSBuild Debugger
Under the HKLM\Software\Microsoft\MSBuild\4.0 key, create a string value called EnableDebugger with a value of . . . → Read More: Debugging MSBuild scripts
Determine the name of the custom action you want to debug
Ensure you have the source code and debug symbols for your custom action
Set the MsiBreak environment variable (user or system) to the name of the custom action. For example:
Setx MsiBreak MyCustomActionName
Run your installer
At the point where your custom action is about to run, you should get . . . → Read More: HOW TO: Debug a Windows Installer custom action
This details how you can debug an application running on a remote machine from Visual Studio on your local machine, as if the remote application was running on your local machine.
The keys are:
There must be a user account with the same username and password on the remote machine and the local machine (MACHINE account, not domain . . . → Read More: Remote debugging from Visual Studio 2008 on a domain machine to a machine not on the domain