Half-Life Server

The Half-Life Dedicated Server (or HLDS) is the dedicated server for hosting a Steam game. It allows you to host a server for any game or modification that works with the Steam client (Half-Life, Counter-Strike, Team Fortress, Ricochet, Day of Defeat, and so on). The dedicated server runs in a console. There are not any GUI releases that I know of.

The linux release can be downloaded from:

Download1 Download2

Most of the time, after downloading these files, you will need to update the release anyways. It might be a good idea to visit ftp://ftp.valvesoftware.com and download hldsupdatetool.bin instead of the large packages from the above links. Login as hlserver, password hlserver. That program will download the latest Steam update utility that is used to download game files for a dedicated server.