Launching a service from msi installer that depends on assemblies installed by the msi

Question

I'm using WiX to write a MSI installer to start a service that depends on DLLs installed by the MSI. On Vista, the DLLs become added to the global assembly cache in the MSI's InstallFinalize phase, so I can't use the built-in service starting command in WiX. That one tries to start the service before the DLLs are in the GAC, and fails. The solution seems to be to use a custom action instead [1], and run that after InstallFinalize.

The custom action I used was starting the service with sc. Everything works fine when running the installer as an administrator, but running as a regular user doesn't work. The installer will elevate privileges for the actual install phase, but will drop them after finalizing the installation, and starting the service with sc as a non-privileged user will fail. Setting the custom action to be deferred and no-impersonate to get admin privileges won't work either after InstallFinalize [2].

As a final kludge, I tried to add <Condition>Privileged</Condition> to the WiX file to tell the user that the installer needs to be run as Administrator, but I couldn't get that to work either. The Privileged value gets set to 1 during the installation, maybe when the main install sequence is given higher privileges.

So has anyone else ran into the combination of Vista, non-Administrator user, installer needs to start a service and service needs stuff that goes into GAC during installation to run? Is there any kind of working general approach to this?

[1] http://www.mail-archive.com/[email protected]/msg09162.html

[2] http://www.mail-archive.com/[email protected]/msg15381.html

Answer 1

This is one of those times when the easiest solution is just to schedule a reboot.

Answer 2

Here are a few possibilities :

• If possible, do not install prerequisite assemblies in the GAC. This will allow your service to be started normally (ie between InstallInitialize and InstallFinalize).

• Create a bootstrapper (a small app that launches prerequisite MSIs in a certain order). Place the prerequisite assemblies (those that go in the GAC) into their own MSI, and get the bootstrapper to install them before it installs your service.

• Create a launcher (an even smaller app that just launches your MSI). Give it a manifest that will make it run elevated. That way, the entire MSI is elevated, not just the part that's between InstallInitialize and InstallFinalize. You should be able to invoke sc succesfully.

Answer 3

I agree with @sascha. Rebooting is not just the easiest but cleanest in this case. All of the other proposed solutions are going to set you up for a much higher failure rate in the future. IMHO, the Windows Installer design w.r.t. the GAC is busted. The reboot is recognition of that.