Windows

SteamCMD

Dedicated servers are now downloaded using SteamCMD. This is a command line version of Steam.

You can download it from this page.

The first time you run it it will update and you will be left at a STEAM> console. You will want to log in. You can log into an anonymous account by typing:

Installing & Updating Garry's Mod Dedicated Server

If you want to specify a download folder then before you update enter this command:

You can then install or update the Garry's Mod Dedicated Server by using the command:

It will slowly download or update.

If you wish to verify your server, enter this instead of the above:

Once it's done you can type quit at the console to exit or just close the SteamCMD window.

Automated

You probably don't want to do that every time you want to install/update a server. Don't worry - it supports command lines too.

Linux

Main article: Linux Dedicated Server Hosting

Installation

Install SteamCMD as per the recommendations from the Valve Developer Wiki.

Then install the GMod dedicated server in a similar manner to Windows:

The server is now available in ~/gmodds/.

Troubleshooting

If you get the error message

You are most likely running 64 a bit system and missing 32 bit libraries.

If the output of this command is x86_64, you are running a 64 bit system and need 32 bit libraries.

See this article on the valve wiki.
32-bit libraries on 64-bit Linux systems

macOS

macOS dedicated servers are no longer shipped.

The Experimental Branches

To update your server to the development branch, you'll have to launch your SteamCMD and enter these commands manually:

For the pre-release branch:

To revert back to stable branch:

The development branch is updated regularly.