Left 4 Dead 2 Dedicated Server Docker Image

"Oh, MAN! This is just like Counter-Strike!"

Source on Github

We also have a Left 4 Dead Docker Image - docker pull left4devops/l4d

Getting Started

Running a vanilla server can as simple as running:

docker run --name l4d2 \
    --network host \
left4devops/l4d2

[!IMPORTANT] The above example uses host networking (--network host), which is the preferred networking method, as it allows the game server to correctly identify the IP of connecting players and can be used to ban players or anyone on the net attempting to force access to RCON. To use host networking on windows or macOS, enable host networking from experimental features in Docker version 4.29.

Bridge Networking Mode

Although the game server won't be able to correctly identify player's IP correctly, you can use Docker's default bridge networking mode instead. Ensure your game port is published using both the TCP and UDP protocols.

docker run --name l4d2-bridged \
    -p 27015:27015/tcp \
    -p 27015:27015/udp \
left4devops/l4d2

Restart behaviour

"Someone needs to restart that generator!"

srcds_run includes a watchdog to restart the server process in the event of a crash. However, you may want to include the restart parameter to ensure your server comes back up after a reboot, like so:

docker run --name l4d2-reboot \
    --restart unless-stopped \
left4devops/l4d2

Denial of Service Protection

"I hate elevators. I hate helicopters. I hate hospitals. And doctors and lawyers and cops..."

This section is in draft, see the discussion here for more detail.

Joining a game

There are a couple of ways you can achieve this:

• Start a lobby, then as host, set the server type to Best Available Dedicated, open the developer console and type mm_dedicated_force_servers [ip:port]. This will try to use your server when the game starts.
• Set the STEAM_GROUP variable and choose to start the game from a Steam Group server in your lobby.
• Add the server as a favourite using the server browser openserverbrowser in game. This will make it appear as a steam group server in the menu.
• Using the developer console, you can connect directly to the server connect [ip:port]
• You can also open the Server Browser from steam under View > Game Servers.
• Servers on your LAN will be shown as Steam Group servers automatically

Custom Addons

If you wanted to play a custom campaign on your server, or include sourcemod, you can mount a directory with any custom content into the /addons/ directory.

e.g. If your working directory had a addons folder:

docker run --name l4d2-server-addons \
    -v $(pwd)/addons:/addons/
left4devops/l4d2

Configuration

Environment Variables

You can pass environment variables to your Docker Container to configure a number of common settings.

HOSTNAME

This is the name of you server, as shown in the Server Browser and Steam Group Servers. Defaults to Left4DevOps.

To change your hostname to BILLS HERE:

docker run --name l4d2-hostname \
    -e HOSTNAME="BILLS HERE" \
left4devops/l4d2

REGION

"I need every one of you inside, now!"

To help hint to Steam where your server is located, set the REGION environment variable as one of the following numeric regions:

If your server was in Europe:

docker run --name l4d2-region \
    -e REGION=3 \
left4devops/l4d2

STEAM_GROUP

Make your server easier to join, by attaching it to a Steam Group. Steam Group Servers are shown in the bottom right corner of the Game menu and can be easily picked as a hosting option in Left 4 Dead 2. In game, players can press h to show the message of the day and then join your steam group, so they can find it again in the future. You can find the ID of your Steam Group at the top of the Admin page.

docker run --name l4d2-group \
    -e STEAM_GROUP=666 \
left4devops/l4d2

STEAM_GROUP_EXCLUSIVE

Normally, your server will be available for anyone using the Best Available Dedicated setting in their lobby. You can prevent this by setting STEAM_GROUP_EXCLUSIVE to true. Any member of your group will be able to start a game as lobby leader.

docker run --name l4d2-group-exclusive \
    -e STEAM_GROUP=666 \
    -e STEAM_GROUP_EXCLUSIVE=true \
left4devops/l4d2

[!NOTE] Non members can still pick your server using mm_dedicated_force_servers

PORT

The game should find the next free port after 27015 to host the game on. If using bridge networking, 27015 will usually be picked automatically, as no other services should be running in the container. You may prefer to hardcode the game port to simply your port forwarding or firewall configuration. Simply set PORT to your desired port. Game traffic and RCON always operate on the same port number.

Change the port with host networking:

docker run --name l4d2-port \
    -e PORT=27016 \
    --network host \
left4devops/l4d2

or if using bridge networking, remember to expose your new ports:

docker run --name l4d2-port-bridged \
    -e PORT=27016 \
    -p 27016:27016/tcp \
    -p 27016:27016/udp \
left4devops/l4d2

To make it slightly less painful to change the port, you could use:

PORT=27017
docker run --name l4d2-port-var \
    -e PORT=$PORT \
    -p $PORT:$PORT/tcp \
    -p $PORT:$PORT/udp \
left4devops/l4d2

[!WARNING] When publishing your ports with bridge networking, ensure the same port is used for both client and host. Otherwise matchmaking will advertise the wrong port and new players will not be able to connect

DEFAULT_MAP

Can be used to set the map when the server is first loaded. Defaults to the newest map for each game. The map names are different in each game. You can get a full list of maps names by typing maps in your Developer Console. To start your L4D2 server on Dead Center:

docker run --name l4d2-map \
    -e DEFAULT_MAP=c1m1_hotel \
left4devops/l4d2

DEFAULT_MODE

Sets the mode used by your server when it is first loaded. Defaults to coop, but can be changed from a lobby.

docker run --name l4d2-mode \
    -e DEFAULT_MODE=versus \
left4devops/l4d2

GAME_TYPES

Can be used to limit which game modes can be played on your server. Leave unspecified to allow all game modes. Values include coop,realism,survival,versus,scavenge,dash,holdout,shootzones

docker run --name l4d2-modes \
    -e GAME_TYPES="versus,mutation19" \
left4devops/l4d2

FORK

Run multiple games from the same container, with ports being automatically allocated by default. The PORT variable is ignored. You can customise the behaviour of the different instances by mounting multiple server##.cfg files.

docker run --name l4d2-forked \
    --network host \
    -e FORK=2
    -v $pwd/server01.cfg:/cfg/server01.cfg
    -v $pwd/server02.cfg:/cfg/server02.cfg
left4devops/l4d2

LAN

Runs the server without needing to talk to Steam, but connecting players need a local IP address.

docker run --name l4d2-lan \
    --network host \
    -e LAN=true \
left4devops/l4d2

RCON_PASSWORD

Son, we're immune, we're tired, and there's infected in the damn woods. Now cut the shit and let us in!

To issue commands to the server whilst you're playing on it, set an RCON password. Logging into a server with RCON also grants you vote kick immunity. To set a password:

docker run --name l4d2-rcon \
    --network host \
    -e RCON_PASSWORD=cuttheshitandletusin \
left4devops/l4d2

Then in game, once you have joined the server, open the Developer Console and type

rcon_password cuttheshitandletusin
rcon

[!NOTE] Make sure the password is unique, as bad actors commonly attempt dictionary ***s. srcds_run will ban an IP after a few failed attempts. This can have the unintended side effect of banning everyone if using bridge networking.

NET_CON_PORT

Similar to RCON, the Network Console allows you to administrator your server, but using a telnet client. If not using a password, I would strongly recommend using a firewall to block public access to the port. To start listening on port ***:

docker run --name l4d2-netcon \
    --network host \
    -e NET_CON_PORT=*** \
left4devops/l4d2

You could then connect using your telnet client:

telnet localhost ***

NET_CON_PASSWORD

To set a net con password:

docker run --name l4d2-netcon-password \
    --network host \
    -e NET_CON_PORT=*** \
    -e NET_CON_PASSWORD=cuttheshitandletusin \
left4devops/l4d2

Once connected via your telnet client, type PASS and then your password:

telnet localhost ***
PASS cuttheshitandletusin

A telnet client is included in the image so you can connect using docker exec:

docker exec -it l4d2 telnet localhost ***

EXTRA_ARGS

Got a small number of other settings you want to add? To spawn larger mobs more frequently:

docker run --name l4d2-args \
    -e EXTRA_ARGS="+z_mega_mob_size 100 +z_mega_mob_spawn_min_interval 180 +z_mega_mob_spawn_max_interval 600" \
left4devops/l4d2

server.cfg

srcds_run will look for a server.cfg file. If you have lots of config, store them in a file and mount it to /cfg/server.cfg.

docker run --name l4d2-server-cfg \
    -v $(pwd)/server.cfg:/cfg/server.cfg
left4devops/l4d2

Command line replacement

You can completely replace the guided environment variable configuration by providing arguments when starting the container

docker run --name l4d2-command-line \
left4devops/l4d2 +hostname "Vannah Hotel"