cs2-server-flux

The Counter-Strike 2 dedicated server for Flux, as runonflux/cs2-server-flux. Valve's native 64-bit Linux server (Steam app 730, anonymous SteamCMD), installed and updated on every start, under a supervisor (bash, PID 1) that:

• builds the launch line from the environment (CS2_*), every value validated
• runs the server in a pseudo-terminal fed by a FIFO, so its console reaches the logs and the hub (flux-console)
• keeps the owner's files on the data volume (cfg/, CounterStrikeSharp's plugins, configs and admins, the two ban lists) and links them into the install; everything else is Valve's, local to the node
• installs and updates Metamod:Source 2.0 and CounterStrikeSharp (with its .NET runtime) when CS2_ADDONS is on, and puts Metamod's line back into gameinfo.gi on every start, because every game update writes that file away
• goes into safe mode (starts without the addons) when a server with them dies twice in a row within 3 minutes of starting, which is what a Valve update that Metamod/CounterStrikeSharp do not support yet looks like; it tries again after an addon update, the next game update, or flux-cs2 addons-retry
• backs up the owner's files on start (unless one is younger than an hour) and every 6 hours
• quits cleanly on stop (inside Docker's 10 s: the server is ended by force at 8 s) and restarts the server in place when it ends on its own, up to 5 times an hour, then exits 42 so the platform rebuilds or moves the container

CS2 has no world to save: everything the panel changes (settings, plugins, admins, bans) is written to the data volume the moment it is made, so a stop or a kill loses nothing.

Volumes

Path	Flux mount	What
/mnt/cs2/data	g: (synced, small)	cfg/ (server.cfg, flux/settings.cfg, flux/mapcycle.txt, plugin cfgs), css/ (plugins, configs, admins, gamedata), banned_user.cfg, banned_ip.cfg, flux/ (backups, addon state)
/mnt/cs2/server	ml:server (local, never synced)	the game, about 69 GB, and the console logs (flux-logs/, 10 MB each, the newest 5) Also flux-logs/flux.log (our supervisor log, 5 MB then one .1): local, never synced.

Spec: g:/mnt/cs2/data|ml:server:/mnt/cs2/server. Never put the server volume on a g: mount: Syncthing would copy 69 GB.

Port

GAME_PORT (27015): the game and the Steam query over UDP, RCON over TCP. SourceTV (27020) is not served by this image.

Environment

Variable
CS2_HOSTNAME	+hostname	63 characters, no double quotes or semicolons
CS2_GAME_MODE	+game_type/+game_mode	competitive (default), casual, wingman, deathmatch, armsrace, custom
CS2_MAP	+map	a map, or a Workshop map as an ID or link (default de_dust2)
CS2_WORKSHOP_COLLECTION	+host_workshop_collection	a Workshop collection's ID or link
CS2_MAXPLAYERS	-maxplayers	2-64 (default 10). The owner's to raise to the game's own 64; hardware is the only limit
CS2_PASSWORD	+sv_password	no spaces or quotes
CS2_RCON_PASSWORD	+rcon_password	empty = RCON off
CS2_GSLT	+sv_setsteamaccount	the owner's own Game Server Login Token for App ID 730 (32 hex characters)
CS2_ADDONS		true (default): Metamod + CounterStrikeSharp. false: off, plugins and configs are kept
CS2_EXTRA_ARGS		appended (no port)
SKIP_UPDATE		true: do not ask Steam for an update on start

The Steam token

Make one at https://steamcommunity.com/dev/managegameservers with App ID 730. Without one the server still runs (it logs in anonymously, measured), but it is not in the Internet server list. A token Steam does not accept (revoked, made for another game, used by another running server) leaves the server disconnected from Steam: measured, status then prints steamid : [I:0:1] and "disconnected from Steam3". flux-cs2 status reports all three as gslt.state (missing / invalid / set) and gslt.login (anonymous / ok / failed) with a message for the panel.

For the hub

flux-console <command> types one command into the server and prints the answer (status, kickid, changelevel, css_plugins list, meta list...).

flux-cs2 prints one JSON document per call:

Command
status	state (updating / starting / running / restarting / stopped / needs-fix / crashed), message, map, mode, players (A2S), build, gslt, addons, last backup
players	the roster: user id, name, bot, SteamID, ping, state, ip (from status + the log's connect lines)
kick <userid> [reason], ban <steamid|ip> [minutes], unban <steamid|ip>	bans are written to the data volume at once
change-map <map|workshop id|link>	changelevel or host_workshop_map
settings / set-settings '<json>'	the Server Settings form (34 settings): definitions and values; validated, written and applied live
files	stock maps, Workshop maps downloaded, map cycle, addons, plugins, the catalogue, admins, bans
set-mapcycle '["de_dust2", ...]'	cfg/flux/mapcycle.txt and the map group mg_flux
plugin-add <id> / plugin-install <zip> / plugin-enable <name> on|off / plugin-remove <name>	CounterStrikeSharp plugins
set-admins '<json>'	css/configs/admins.json, merged
addons-retry	leave safe mode
backups / restore <backup>

needs-fix is a state the environment causes and a restart cannot cure (a GAME_PORT that is not a port): the container waits for a redeploy instead of crash-looping.

/tmp/flux-generation holds <generation> <epoch>: a restart is over when it changes.

Plugin catalogue (scripts/plugins.json)

Only plugins that load cleanly on the current build (CounterStrikeSharp 1.0.377, game 1.41.9.1): MatchZy, Retakes (+ Instadefuse, Clutch Announce), Deathmatch, GG1 MapChooser. Retakes and Deathmatch conflict (the catalogue says so).

Tests

./tests/test-flux.sh                                   # unit tests, no Docker
docker build -t cs2-server-flux:local .
./tests/test-image.sh                                  # the real supervisor around a stand-in Steam and server
docker run --rm -v "$PWD:/mnt" -w /mnt koalaman/shellcheck:stable -x scripts/*.sh tests/*.sh tests/image/*.sh

Measured (build 1.41.9.1)

• 69 GB installed (csgo 61 GB, community addons 6.4 GB); the download is 73 GB.
• Up in about 6 s on an installed volume (plus the SteamCMD check); idle (hibernating, nobody on) 1.08 GiB RAM, about 3 % of one core; 15 bots awake 1.30 GiB, about 24 % of one core.
• docker stop 3.5-4.5 s with six plugins loaded.

Versions

• 1.0.0: first release.
• 1.0.3: the progress line SteamCMD ends with (unknown, progress: 0.00 (0 / 0)) is ignored. Format checked against real SteamCMD output (app 1007).
• 1.0.2: SteamCMD's download progress in flux-cs2 status (progress: phase, percent, bytes) while updating; timed bans survive a restart (banned_timed.json on the data volume, put back at each start with the minutes they have left through cfg/flux/timedbans.cfg; listed by flux-cs2 files with timed: true); flux-cs2 workshop-remove <id> deletes a downloaded Workshop map and its manifest entry (refused while it is played).
• 1.0.1: flux.log moved off the synced data volume to /mnt/cs2/server/flux-logs/flux.log (5 MB, one .1; an old one is moved there once); start-up banner; the weekly rebuild only when it has something to apply (new script .github/ci/needs-rebuild.sh).