Windows Service: Can I configure the current working directory?

By default, Windows services start in the sytem32 directory (usually C:\WINDOWS\system32).

Is there a way to set up a different working directory? I am thinking of some registry parameter beneath HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SomeService.

So - can this be done?

From serverfault Tomalak

• Like MattB, I don't know of any way to change the service's working directory w/o access to the source code. For this specific scenario, it's likely that the extra directory checks don't impose that much unnecessary disk activity relative to the amount of i/o required for the full text indexing operation. Even if you could optimize them away, the full text index will be disk intensive by the nature of the beast.

  From Fred

• You could use DLL injection to call SetCurrentDirectory after the process has already launched. This would require you to build an injector application, plus the DLL to inject. Some tutorials exist; probably the two best ones I've found are:

  • Three ways to inject your code into another process
  • Extending task manager with DLL injection

  You'll need a decent amount of C++ programming background (and a working build environment) to get through that.

  However, this assumes that the service is looking at the current directory. Another possibility is that it's using %path%. You say that it "starts at system32, tries a few more locations, and eventually its own directory", so this seems more likely to me.

  Compare the directories you see in procmon with your %path%. If they're the same, consider modifying either the SYSTEM %path% or the %path% of the user running the service, so that the directory you want it to search is first.

  I believe Fred is right, though -- you're unlikely to see any significant performance benefit by doing any of this, unless it's happening very frequently. Simple file open operations are not particularly expensive, especially if it's a local path and the file doesn't actually exist.

  Marnix van Valen : The system PATH environment variable was the first thing that came to mind for me. Inserting the service's path at the start of the PATH variable will however have a negative effect on the performance of just about every other application so I wouldn't advise that.

  fission : I don't have hard numbers to back this up either way, but my intuition tells me that no practical performance gain or loss would occur from modifying the path. This is a fairly common scenario; nobody blames, say, the Windows Support Tools, or SQL Server, for negatively impacting system performance when it modifies the path during installation. This isn't the first time I've seen someone look at procmon and go "omg, look at all those file accesses!", not realizing that it's typical for most applications.

  Tomalak : +1 for creativity. :-) I fully understand that these file operations do not impact performance measurably, so I'm not going to actually bother writing a DLL injection solution. Modifying `%PATH%` for the user account the service runs under is a decent idea, though.

  fission : Thanks! Does this mean you're accepting my answer? :D

  Sunny : Creating a special user to run this service only and modifying the %PATH% for this user sounds as a very good way to go. +1

  Tomalak : @fission: Yes, it does mean I accept your answer. ;) It's not what I had hoped for, but it is as close as it gets, I guess.
  From fission