As described in that post I edited the file and added the entries:
sdtd hard nofile 16384sdtd soft nofile 8192
I even rebooted after that but no luck im afraid
2014.09.04 17:44:36: Exception: ServicesGameServer.Initialize failed: SteamInitializeFailed
2014.09.04 17:44:36: at ManagedSteam.ServicesGameServer.Startup (UInt32 ip, UInt16 steamPort, UInt16 gamePort, UInt16 queryPort, ServerMode serverMode, System.String versionString) [0x00000] in <filename unknown>:0
2014.09.04 17:44:36: at ManagedSteam.ServicesGameServer.Initialize (System.Globalization.CultureInfo activeCulture, UInt32 ip, UInt16 steamPort, UInt16 gamePort, UInt16 queryPort, ServerMode serverMode, System.String versionString) [0x00000] in <filename unknown>:0
2014.09.04 17:44:36: at ManagedSteam.ServicesGameServer.Initialize (UInt32 ip, UInt16 steamPort, UInt16 gamePort, UInt16 queryPort, ServerMode serverMode, System.String versionString) [0x00000] in <filename unknown>:0
2014.09.04 17:44:36: at SteamMasterServer.Connect (UnityEngine.MonoBehaviour _mono) [0x00000] in <filename unknown>:0
2014.09.04 17:44:36: at GameManager.md0011 () [0x00000] in <filename unknown>:0
2014.09.04 17:44:36: at GameManager.Awake () [0x00000] in <filename unknown>:0
2014.09.04 17:44:36: Unloading 5 Unused Serialized files (Serialized files now loaded: 1 / Dirty serialized files: 0)
2014.09.04 17:44:36: Unloading 153 unused Assets to reduce memory usage. Loaded Objects now: 94076.
2014.09.04 17:44:36: Total: 116.552002 ms (FindLiveObjects: 5.977000 ms CreateObjectMapping: 0.578000 ms MarkObjects: 109.618004 ms DeleteObjects: 0.298000 ms)
Then a player tried to join which failed => 2014.09.04 17:45:04: ServicesGameServer not initialzed!
I found a few more things, though some of them were occuring before that error:
2014.09.04 17:43:51: The file '/home/sdtd/engine/7DaysToDie_Data/mainData' is corrupted! Remove it and launch unity again!
2014.09.04 17:43:51: [Position out of bounds! 931644 > 931640]
2014.09.04 17:43:51: The class named 'Localization' is abstract. The script class can't be abstract!
2014.09.04 17:43:56: The file '/home/sdtd/engine/7DaysToDie_Data/level0' is corrupted! Remove it and launch unity again!
2014.09.04 17:43:56: [Position out of bounds! 162972 > 162968]
2014.09.04 17:43:56: The file '/home/sdtd/engine/7DaysToDie_Data/level0' is corrupted! Remove it and launch unity again!
2014.09.04 17:43:56: [Position out of bounds! 163560 > 163556]
I dont think the last messages are interesting though. Weirdly enough my other Instance which is Navezgane based with close to 0 players is still running and can be restarted..
Any more ideas :/ ?