patch notes
Left 4 Dead 2 Patch Left 4 Dead 2 - Update
Fixed a compatibility issue causing crashes on Linux clients.
Source: Steam NewsLeft 4 Dead 2 Network Updates
Server changes, patches, and networking updates for Left 4 Dead 2.
patch notes
Left 4 Dead 2 gets a compatibility update for Linux
Valve released a compatibility update to fix issues caused by glibc version 2.41 on Linux.
Source: Steam News