General dedicated server changes for Left4Dead:===============================================* There is a new remote access feature which allows a server administrator (or software tool) to create a persistent connection to a running server, and to see its entire console output and send it commands. This feature is enabled by using the "-netconport" option when launching srcds. For instance, if a server is started with "-netconport 9000", someone with access to port 9000 of the server could type "telnet xxxx 9000" and view the console output. This feature is disabled by default, and should only be used when an appropriate firewall/tunnel is used to control access to this port. Multiple clients can connect to the netconport of a running server at the same time.* If the netconsole is enabled, and the option "-netconpassword xxx" is set, the network console will not execute commands received through the netconport until the command "PASS xxx" is entered.* Dedicated servers by default participate in matchmaking. Matchmaking system allows players to get together in a lobby and then start a game on a dedicated server together. To make your Left 4 Dead dedicated server easily accessible to your community you would create a Steam group and get its group id on Steam community group admin page (say "444"). Set "sv_steamgroup 444" to make all members of your Steam group have access to the server from their main menu. You can also set "sv_steamgroup_exclusive 1" which will require that at least one player from your Steam group has to join the server before public people will be able to join via matchmaking.Linux-specific dedicated server changes for Left4Dead=====================================================There have been many changes, enhancements, and optimizations with thededicated server for Linux:* All of the code is now being compiled with gcc 4.3.0 and glibc 2.8-8 in order to take advantage of compiler fixes and optimization enhancements. In order to run the l4d Linux dedicated server, you will need a system which can run binaries built against this version of glibc.* As a performance enhancement, the dedicated server can now use the hardware "RDTSC" timer instead of gettimeofday() for its internal timing, on systems which support it ( such systems are identified by having the "constant_tsc" flag set in /proc/cpuinfo ). When the code detects that the system has this, it will execute a benchmark to measure the actual rate of the hardware timer, and use this for all timing. If this causes trouble on a system, you can set the environment variable "RDTSC_FREQUENCY" to "disabled".* The Linux dedicated server is now capable of running multiple server instances as sub-processes off of one parent process. This provides a memory savings (through sharing of read-only data), a speedup when starting multiple servers, and also enhances server stability by having the servers restart as new sub-processes after each game is completed. This is controlled by the "-fork n" option. For instance, you can run "srcds_run -fork 5" to start up 5 separate server instances in this mode.* When -fork mode is enabled, some options on the command line can be parametrized based upon the server instance, by typing '##' on the launching line. For instance, "-fork 10 -netconport 90##" would cause the first server instance to use port 9001, the second to use 9002, etc.* When running with -fork mode and a netconsole, the control/parent process will also listen on a port and accept commands. For instance, if you start the server with "-fork 10 -netconport 90##", the parent will accept netconsole connections on port 9000, the first child will accept netconsole connections on port 9001, etc. You can see a list of commands accepted by the parent process by connecting to it and typing "find". useful commands are: status see status of all children. shutdown cleanly shutdown the server when all games have finished. broadcast execute the console command 'cmd' on all active subprocesses. Note that this netconsole also obeys the set -netconpassword. You should always set a password unless you are otherwise protecting access to your netconsole ports (for insatnce via a firewall/ssh tunnel).* The linux dedicated server supports a watchdog timer functionality, which is enabled by default. The intent of this timer is to make anything which hangs the server, either due to unknown bugs or misconfiguration, cause an abort, so that the server may restart or be debugged. In the case of a forked server, this will cause a new subprocess to start to replace the crashed one. On a non-forked server, this can be used in conjunction with an auto-restart script in order to increase server availability. If you see your server dying with SIGALRM (signal 14), it means that this has triggered because of either a server frame taking longer than 5 seconds of wall time, or a map load taking too long. If this code causes trouble for you, it can be disabled via giving the "-nowatchdog" option on the command line.