Installing and running a server for PVKII 2.6 is a bit different from previous releases because PVKII recently moved to the new SteamPipe content system. SteamCMD is a new tool for installing and updating servers for SteamPipe games. See https://developer.valvesoftware.com/wiki/SteamCMD
for more details.
The following instructions attempt to explain the steps needed to download and run the PVKII dedicated server in a concise way.
1. Download and run the SteamCMD executable
Windows - http://media.steampowered.com/client/steamcmd_win32.zip
Linux - http://media.steampowered.com/client/steamcmd_linux.tar.gz
Extract the contents to a directory and execute steamcmd.exe (or ./steamcmd.sh on Linux)
2. Use SteamCMD to download the PVKII dedicated server
Before you can download apps, SteamCMD requires you to login. You can login anonymously by typing in the command:
Once you are logged in, you can specify the directory path where you want to download the dedicated server package. For example, if you run the following command SteamCMD will download the package into a sub-directory named pvkii inside the SteamCMD directory:
To begin downloading the PVKII dedicated server package type in the command:
app_update 17575 validate
Once the download finishes, you'll find srcds.exe in the directory you specified before. At this point you can close SteamCMD.
3. Running the server
Running the server is the same as before SteamPipe. For example, to launch a 18 player server on map bt_island, you can execute:
srcds.exe -console -game pvkii -maxplayers 18 +map bt_island
./srcds_run -console -game pvkii -maxplayers 18 +map bt_island
4. Updating the server when updates are released
When new updates are released to the game, you'll have to run SteamCMD again. Use the same commands as in part 2 above to update your server.
To make this easier in the future, you can make a shortcut for SteamCMD that automates the update process. If you give the following parameters to SteamCMD, the program will log in, run the app_update command and then quit.
steamcmd +login anonymous +force_install_dir ./pvkii +app_update 17575 validate +quit
Thanks to Akz for this guide.