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README.md
spigot

README.md

SpigotMC - High Performance Minecraft Server


About this image

This Docker image allows you to get a Spigot instance quickly, with minimal fuss.

This image was based on the dlord/minecraft Docker Image, with a few changes and enhancements.

Base Docker image

  • java:8

How to use this image

Starting an instance

docker run \
    --name spigot-instance \
    -p 0.0.0.0:25565:25565 \
    -d \
    -it \
    -e DEFAULT_OP=dinnerbone \
    -e MINECRAFT_EULA=true \
    dlord/spigot

By default, this starts up a Spigot 1.12.2 server instance. If you wish to start a different server version, you need to set the MINECRAFT_VERSION variable to the appropriate version. You will need to check Spigot's documentation to determine the supported Spigot versions.

You must set the DEFAULT_OP variable on startup. This should be your Minecraft username. The container will fail to run if this is not set.

When starting a Spigot instance, you must agree to the terms stated in Minecraft's EULA. This can be done by setting the MINECRAFT_EULA variable to true. Without this, the server will not run.

This image exposes the standard minecraft port (25565).

When starting a container for the first time, it will check for the existence of the Spigot jar file. If this does not exist, it will download BuildTools and compile Spigot from source. As much as I want to provide the precompiled binaries, I am avoiding any legal complications.

It is highly preferred to start the container with -it. This is needed in order to allow executing console commands via docker exec. This also allows Spigot to safely shutdown when stopping the container via docker stop. See the Scripting section for more details.

Commands

The image uses an entrypoint script called spigot, which allows you to execute preset commands. Should you attempt to execute an unrecognized command, it will treat it as a regular shell command.

The commands are as follows:

  • run - This runs the Spigot server, and is the default command used by the container. This command can accept additional parameters. Useful when creating a new container via docker create or docker run
  • permissions - This updates the permissions of all related files and folders. Useful when manually editing a file.
  • console - This executes a console command. This allows system administrators to perform complex tasks via scripts. This feature is off by default. See the Scripting section for more details and examples.

Here are some examples on how to use these commands:

run - specify a different Spigot configuration file inside /opt/minecraft

docker run \
    --name spigot-instance \
    -p 0.0.0.0:25565:25565 \
    -d \
    -it \
    -e DEFAULT_OP=dinnerbone \
    -e MINECRAFT_EULA=true \
    dlord/spigot
    run --spigot-settings spigot-test.yml

permissions - update file and folder permissions while a container is running

docker exec spigot-instance spigot permissions

Scripting

Unlike other Spigot Docker Images, this image provides a way to execute console commands without attaching to the docker container. It lets system administrators perform much more complex tasks, such as managing the docker container from another docker container (e.g. deploying using Jenkins).

For those who are used to running docker attach inside a screen or tmux session for scripting, this is going to be heaven.

This feature can be enabled by pasing the -it parameter to docker create or docker run, which enables STDIN and TTY. This runs the Spigot server inside a tmux session. This also enables safe shutdown mode when the container is stopped.

Once enabled, you may now execute console commands like so:

docker exec spigot-instance spigot console say hello everybody!

Some warnings when using this feature:

  • DO NOT USE -it ON docker exec! For some reason, it crashes the tmux session that drives this feature.
  • Be careful when attaching to the console via docker attach. You are attaching to a tmux session running on the foreground with the footer disabled. Do not try to detach from the tmux session using CTRL-b d, otherwise this will stop the container. To detach from the container, use CTRL-p CTRL-q, which is the standard escape sequence for docker attach.

Here is an example on how to notify players that the server will be shutdown after 60 seconds:

#!/bin/bash
docker exec spigot-instance spigot console say We will be shutting down the server in 60s!
docker exec spigot-instance spigot console say Stop whatever you are doing!
sleep 60
docker exec spigot-instance spigot console say We will be back in 1 hour!
sleep 5

# The container will send the stop console command to the server for you, to
# ensure that the server is shutdown safely.
#
# Of course you can run this manually like so:
#
#     docker exec spigot-instance spigot console stop
#
# But this will restart the container if the restart policy is set to always.
docker stop -t 60 spigot-instance

Spigot BuildTools Caveat

One major problem with Spigot's BuildTools is that it doesn't entirely respect the server version you want to compile. If the specified MINECRAFT_VERSION does not exist, it will always compile the latest version. And if the compiled jar version does not match the MINECRAFT_VERSION, this will cause the container to stop.

Given my limited knowledge of dealing with bash scripts, I currently have no way of detecting what version was compiled.

Should this happen, you may opt to copy the compiled jars to a data volume mapped to MINECRAFT_HOME (default is /opt/minecraft), and use that to start a new container with the appropriate MINECRAFT_VERSION.

Data volumes

The entrypoint script updates the permissions of the data volumes before running Spigot. You are free to modify the contents of these directories without worrying about permissions.

There are two data volumes declared for this image:

/opt/minecraft

All server-related artifacts (jars, configs)' go here.

/var/lib/minecraft

This contains the world data. This is a deliberate decision in order to support building Docker images with a world template (useful for custom maps).

The recommended approach to handling world data is to use a separate data volume container. You can create one with the following command:

docker run --name minecraft-data -v /var/lib/minecraft java:8 true

Environment Variables

The image uses environment variables to configure the JVM settings and the server.properties.

MINECRAFT_EULA

MINECRAFT_EULA is required when starting creating a new container. You need to agree to Minecraft's EULA before you can start Spigot.

DEFAULT_OP

DEFAULT_OP is required when starting creating a new container.

MINECRAFT_OPTS

You may adjust the JVM settings via the MINECRAFT_OPTS variable.

Environment variables for server.properties

Each entry in the server.properties file can be changed by passing the appropriate variable. To make it easier to remember and configure, the variable representation of each entry is in uppercase, and uses underscore instead of dash.

The server port cannot be changed. This has to be remapped when starting an instance.

For reference, here is the list of environment variables for server.properties that you can set:

  • GENERATOR_SETTINGS
  • OP_PERMISSION_LEVEL
  • ALLOW_NETHER
  • LEVEL_NAME
  • ENABLE_QUERY
  • ALLOW_FLIGHT
  • ANNOUNCE_PLAYER_ACHIEVEMENTS
  • LEVEL_TYPE
  • ENABLE_RCON
  • FORCE_GAMEMODE
  • LEVEL_SEED
  • SERVER_IP
  • MAX_BUILD_HEIGHT
  • SPAWN_NPCS
  • WHITE_LIST
  • SPAWN_ANIMALS
  • SNOOPER_ENABLED
  • ONLINE_MODE
  • RESOURCE_PACK
  • PVP
  • DIFFICULTY
  • ENABLE_COMMAND_BLOCK
  • PLAYER_IDLE_TIMEOUT
  • GAMEMODE
  • MAX_PLAYERS
  • SPAWN_MONSTERS
  • VIEW_DISTANCE
  • GENERATE_STRUCTURES
  • MOTD

Extending this image

This image is meant to be extended for packaging custom maps, plugins, and configurations as Docker images. For server owners, this is the best way to roll out configuration changes and updates to your servers.

If you wish to do so, here are some of the things you will need to know:

ONBUILD Trigger

This Docker image contains one ONBUILD trigger, which copies any local files to /usr/src/minecraft.

When a container is started for the first time, the contents of this folder is copied to MINECRAFT_HOME via rsync, except for anything that starts with world. It will also ensure that the MINECRAFT_HOME/plugins folder exists, and it will clean out any plugin jar files to make way for new ones. This is the simplest way to roll out updates without going inside the data volume.

World Templates

This Docker image supports the use of world templates, which is useful for packaging custom maps. World templates should always start with world, which has been a standard Minecraft convention (e.g. world, world_nether, world_the_end). Copy your world templates to /usr/src/minecraft via the ONBUILD trigger. During startup, it will check if /var/lib/minecraft is empty. If so, it will create a copy of the world template on this folder.

JVM Arguments

You can include them via the MINECRAFT_OPTS variable in your Dockerfile.

Supported Docker versions

This image has been tested on Docker version 1.9

Feedback and Contributions

Feel free to open a Github issue.

If you wish to contribute, you may open a pull request. I am very strict with commit standards, and pull requests with no descriptions will be closed immediately.

For commit standards, I follow a similar style to the Linux Kernel. See section 1.2 of the How to Get Your Change Into the Linux Kernel. For examples and tips, check out this guide by Chris Beams.