There seems to be a lot of confusion about how to run games built on the Unity engine distributed by Steam on a Linux system. I recently solved this problem after backing the promising survival sandbox game Planet Nomads on Kickstarter. Here is how to configure an Ubuntu Linux system and launch Planet Nomads successfully.
If you have an Nvidia card, you must download and install the official proprietary drivers provided by Nvidia. I could not get Unity to launch with the open-source drivers. Once I installed the proprietary (closed source) drivers, I was able to launch Planet Nomads from the Steam application.
Launching on Linux
When you need to troubleshoot something, there is no substitute for using the command line. At this point, forget about Steam altogether. Open a terminal and run the following command. Once you get it working, you can create a “launcher” or shortcut in your desktop environment so that you won’t have to remember the command. It also may run directly from Steam once you’ve solved the underlying problem.
Open a terminal and type the following command to launch Planet Nomads. For other games build on Unity and distributed using Steam, use a similar command, but change the command to reflect the actual path to the game binary:
I’m assuming you are already familiar with running commands in a terminal. If this Unix/Bash syntax is confusing, please post a comment and I will explain.
When the game launches successfully, the output looks like this:
Found path: /home/your_username/.steam/steam/steamapps/common/Planet Nomads/PlanetNomads.x86_64
Mono path = '/home/your_username/.steam/steam/steamapps/common/Planet Nomads/PlanetNomads_Data/Managed'
Mono path = '/home/your_username/.steam/steam/steamapps/common/Planet Nomads/PlanetNomads_Data/Mono'
Mono config path = '/home/your_username/.steam/steam/steamapps/common/Planet Nomads/PlanetNomads_Data/Mono/etc'
displaymanager : xrandr version warning. 1.5
client has 4 screens
displaymanager screen (0)(DVI-D-0): 1920 x 1080
Using libudev for joystick management
Importing game controller configs
You can specify a log file to hold full output from the game launch:
~/.steam/steam/steamapps/common/Planet\ Nomads/PlanetNomads.x86_64 -logfile ~/planetnomads_log.txt
Note that even a successful launch of the game will create some misleading errors in the log, such as:
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object
at Database.SQLite.Finalize () [0x00000] in :0
[Steamworks.NET] SteamAPI_Init() failed. Refer to Valve's documentation or the comment above this line for more information.
(Filename: /home/builduser/buildslave/unity/build/artifacts/generated/common/runtime/UnityEngineDebugBindings.gen.cpp Line: 42)
Note that these “error” messages do not impact your ability to play the game!