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RCON commands can be configured to execute automatically when specific server events occur, such as server startup, player connections, or player disconnections. This enables powerful automation for server management, gameplay modifications, and player interactions.

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Event Types

RCON commands can be triggered on these events:
  • Server startup - Commands run once when the server starts
  • Client connect - Commands run when any player connects
  • Client disconnect - Commands run when any player disconnects
  • First client connect - Commands run when the first player joins an empty server
  • Last client disconnect - Commands run when the last player leaves

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Configuration Variables

VariableTriggerDescription
RCON_CMDS_STARTUPServer startCommands executed once on server startup
RCON_CMDS_ON_CONNECTPlayer joinsCommands executed when any player connects
RCON_CMDS_ON_DISCONNECTPlayer leavesCommands executed when any player disconnects
RCON_CMDS_FIRST_CONNECTFirst player joinsCommands executed when first player joins empty server
RCON_CMDS_LAST_DISCONNECTLast player leavesCommands executed when last player leaves server
When declaring multiple commands in a compose file, use YAML’s |- block style indicator for better readability.

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Server Startup Commands

Execute commands once when the server starts: 
services:
  mc:
    image: itzg/minecraft-server
    environment:
      EULA: "TRUE"
      RCON_CMDS_STARTUP: |-
        gamerule doFireTick false
        pregen start 200
        time set day

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Common Startup Use Cases

RCON_CMDS_STARTUP: |-
  gamerule keepInventory true
  gamerule mobGriefing false
  gamerule doFireTick false
  difficulty normal

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Player Connection Commands

Execute commands when any player connects to the server: 
environment:
  RCON_CMDS_ON_CONNECT: |-
    team join New @a[team=]
    give @a[team=New] diamond 1
On client connect, you only know there was a connection, not which specific player connected. Use RCON selector commands like @a[team=] to target players.

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Connection Use Cases

RCON_CMDS_ON_CONNECT: |-
  team join New @a[team=]
  give @a[team=New] wooden_sword
  give @a[team=New] bread 16
  team join Old @a[team=New]

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Player Disconnect Commands

Execute commands when any player disconnects: 
environment:
  RCON_CMDS_ON_DISCONNECT: |-
    say A player has left the server
    gamerule doFireTick true

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Disconnect Use Cases

environment:
  RCON_CMDS_ON_DISCONNECT: |-
    say Goodbye, player!
    # Clean up temporary entities
    kill @e[type=item,distance=..100]

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First Player Connect

Execute commands when the first player joins an empty server: 
environment:
  RCON_CMDS_FIRST_CONNECT: |-
    pregen stop
    gamerule randomTickSpeed 3
    say Server is now active!

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First Connect Use Cases

RCON_CMDS_FIRST_CONNECT: |-
  pregen stop
  gamerule doMobSpawning true
  gamerule randomTickSpeed 3
  weather clear

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Last Player Disconnect

Execute commands when the last player leaves the server: 
environment:
  RCON_CMDS_LAST_DISCONNECT: |-
    kill @e[type=minecraft:boat]
    pregen start 200
    save-all

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Last Disconnect Use Cases

RCON_CMDS_LAST_DISCONNECT: |-
  kill @e[type=item]
  kill @e[type=minecraft:boat]
  save-all
  say Server entering idle mode

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Complete Example: New Player Management

This example uses teams to track and welcome new players: 
services:
  mc:
    image: itzg/minecraft-server
    ports:
      - "25565:25565"
    environment:
      EULA: "TRUE"
      VERSION: "1.20.4"
      
      # Initialize teams on startup
      RCON_CMDS_STARTUP: |-
        /pregen start 200
        /gamerule doFireTick false
        /team add New
        /team add Old
      
      # Welcome new players with starter items
      RCON_CMDS_ON_CONNECT: |-
        /team join New @a[team=]
        /give @a[team=New] birch_boat
        /give @a[team=New] bread 16
        /team join Old @a[team=New]
      
      # Stop pre-generation when first player joins
      RCON_CMDS_FIRST_CONNECT: |-
        /pregen stop
        /gamerule doFireTick true
      
      # Cleanup and restart pre-gen when last player leaves
      RCON_CMDS_LAST_DISCONNECT: |-
        /kill @e[type=minecraft:boat]
        /save-all
        /pregen start 200
        /gamerule doFireTick false
    
    volumes:
      - ./data:/data

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How This Example Works

1

Server starts

Creates “New” and “Old” teams, starts chunk pre-generation, disables fire spread.
2

First player joins

Stops pre-generation, enables fire spread.
3

Player connects

If player has no team (new player), joins them to “New” team, gives starter items, then moves to “Old” team.
4

Last player leaves

Cleans up boats, saves world, restarts pre-generation, disables fire spread.

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Advanced Examples

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Dynamic Difficulty Scaling

environment:
  RCON_CMDS_FIRST_CONNECT: |-
    difficulty easy
  
  RCON_CMDS_ON_CONNECT: |-
    execute store result score PlayerCount global if entity @a
    execute if score PlayerCount global matches 3.. run difficulty normal
    execute if score PlayerCount global matches 5.. run difficulty hard
  
  RCON_CMDS_ON_DISCONNECT: |-
    execute store result score PlayerCount global if entity @a
    execute if score PlayerCount global matches ..2 run difficulty easy
    execute if score PlayerCount global matches 3..4 run difficulty normal

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Auto-Save on Disconnect

environment:
  RCON_CMDS_ON_DISCONNECT: |-
    save-all
    say World saved!
  
  RCON_CMDS_LAST_DISCONNECT: |-
    save-all
    say All players gone. World saved and entering idle mode.

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Timed Events on First Join

environment:
  RCON_CMDS_FIRST_CONNECT: |-
    schedule function mypack:start_event 100t
    say Event starting in 5 seconds!
    gamerule doDaylightCycle true

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Troubleshooting

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Commands Not Executing

Verify RCON is enabled and check command syntax: 
# Check RCON connection
docker exec mc rcon-cli ping

# Test command manually
docker exec mc rcon-cli "gamerule doFireTick false"

# View logs for RCON errors
docker logs mc | grep -i rcon

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YAML Syntax Issues

Ensure proper YAML formatting: 
# Correct: Use |- for multi-line
RCON_CMDS_STARTUP: |-
  command1
  command2

# Incorrect: Don't use quotes with |-
RCON_CMDS_STARTUP: "|-
  command1"

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Commands with Special Characters

Escape or quote commands with special characters: 
RCON_CMDS_STARTUP: |-
  say Welcome to "My Server"!
  tellraw @a {"text":"Hello World","color":"gold"}

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Best Practices

  1. Test commands manually before automating them
  2. Use block style (|-) for readability with multiple commands
  3. Be cautious with destructive commands like /kill or /clear
  4. Log important actions using /say for debugging
  5. Combine with scoreboard for advanced logic
  6. Use selectors properly since player names aren’t available on connect events

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Reference

For RCON command syntax, see:

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