> Global Assembly Cache Tool

Where is gacutil.exe on my Windows server?

All of our production servers run Microsoft Windows Server 2008, and we keep the environment clean and lightweight. For example, we never install office productivity tools (like Microsoft Office) or integrated development tools (like Visual Studio) on our production servers. This keeps the attack surface small, and it helps to ensure that the server runs as fast as possible - without any potential for being bogged down by unnecessary applications.

We have a number of web applications on one server in particular, and all of these applications rely on a Microsoft.NET assembly from a third-party. At 14 MB, the DLL is relatively large, and so we decided to move the DLL into the Global Assembly Cache (GAC). Until now, a copy of the DLL has been installed in the bin directory for every application that uses it. This is wasteful of resources, and more difficult to maintain when the vendor releases updates to the assembly.

You will recall that the global assembly cache is machine-wide code cache that stores assemblies that are specifically intended for sharing by several applications on the computer. The Global Assembly Cache Tool (gacutil.exe) allows you to install assemblies into the cache, remove them from the cache, and list the contents of the cache. Using the tool to install an assembly into the cache is simple:

C:\> gacutil /i mydll.dll

According to Microsoft, gacutil.exe is considered to be a development tool. Because of this, it is only contained in the .NET SDK and not in the .NET redistributable. Visual Studio comes with the SDK, so all Visual Studio users have the tool installed.  On my development machine it is located here:

C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\NETFX 4.0 Tools\x64\

Our production server has the .NET redistributable installed, but it does not have Visual Studio or the .NET SDK installed, therefore this folder does not exist on our production server.

The simplest solution is to download and install the Microsoft Windows SDK for Windows 7 and .NET Framework 4.  Version 7.1, published May 19, 2010, is available for free download here: 

www.microsoft.com/download/en/details.aspx?id=8279

After downloading winsdk_web.exe, run the program with administrator permissions, and select the .NET Installation Options. 

The installation takes a few minutes to run, and after it completes the Global Assembly Cache Tool is ready to use.

C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\NETFX 4.0 Tools\gacutil.exe

I found this to be the simplest solution, although there are alternatives for installing assemblies in the GAC without using gacutil.exe:

  1. If you have developed the application yourself you can use the GacInstall method. For more information, refer to the class documentation for System.EnterpriseServices.Internal.Publish.
  2. Create a PowerShell script that wraps the Publish.GacInstall function. Here is one example.
  3. Create a Microsoft Installer (MSI) package to deploy the assembly. Microsoft provides help documentation for this, and instructive tutorials are also available.