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Minecraft - Vanilla Server

About this image

This Docker image allows you to run a Vanilla Minecraft server quickly. It also serves as the base image for some of my Modded Minecraft server images.

Available Tags

• java15, latest - the default. Uses Shenandoah GC by default for low latency.
• java8 - used by certain modpacks, or for people who know what they are doing.
• java7 - for backward compatibility with older Minecraft versions.

How to use this image

Starting an instance

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

By default, this starts up a Minecraft 1.8.8 server instance. If you wish to start a different Minecraft server version, you need to set the MINECRAFT_VERSION variable to the appropriate version.

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 Minecraft server, 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 Minecraft Server jar file, and will download from Mojang when necessary. As much as I want to package the Minecraft server jar in this image (to also save on time and the hassle of an extra step), I cannot due to the Minecraft EULA.

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 the Minecraft server 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 minecraft, 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 Minecraft server, and is the default command used by the container. This command can accept additional parameters (if minecraft supports other options apart from nogui). 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 - pass anotherminecraftoptionthatdoesnotexist to minecraft server

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

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

docker exec minecraft-instance minecraft permissions

Scripting

Unlike other Minecraft 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 Minecraft 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 minecraft-instance minecraft 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 minecraft-instance minecraft console say We will be shutting down the server in 60s!
docker exec minecraft-instance minecraft console say Stop whatever you are doing!
sleep 60
docker exec minecraft-instance minecraft 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 minecraft-instance minecraft console stop
#
# But this will restart the container if the restart policy is set to always.
docker stop -t 60 minecraft-instance

Data volumes

Previously, this image has one data volume: /var/lib/minecraft. This volume used to contain world data. If you are using an older version of this docker image, you will need to move the contents of this folder to /opt/minecraft.

The decision to change this was due to the way Vanilla Minecraft works.

Unlike Spigot, which is capable of changing the location of the world data, Vanilla Minecraft (and by extension, Modded Minecraft), does not play nice with this. Even though they technically support it, mods and other sysads expect the world data to reside inside the main Minecraft folder.

And when you try to support both vanilla and modded servers, it becomes more complex. Vanilla servers will have 3 world folders (e.g. world, world_nether, world_the_end), while modded servers will only have world.

To keep things simple, I've removed the data volume definition. It is now up to the user to declare the appropriate data volume either at runtime, or when extending the image.

If you're running a Vanilla server, you may opt to declare /opt/minecraft as a data volume. This not only simplifies data management, it allows you to take advantage of the ONBUILD trigger that comes with this image. See the ONBUILD Trigger section for details.

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 the Minecraft server.

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

On startup, it will check the existence of server.properties. If it does not exist, one will be created for you. You may override the defaults by setting the appropriate environment variable.

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, modpacks, 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 /opt/minecraft via rsync, except for anything that starts with world.

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 /opt/minecraft/world is empty. If so, it will create a copy of the world template on this folder.

Environment Variables in Dockerfile

MINECRAFT_HOME (Read-only!)

To make your life simple, this variable points to where Minecraft is installed. This points to /opt/minecraft. Useful for creating scripts when packaging modpacks.

DO NOT OVERRIDE THIS. CHANGES TO THIS VARIABLE ARE IGNORED!

MINECRAFT_VERSION

Modpacks will require a specific Minecraft version in order to work. This can be done setting the MINECRAFT_VERSION in your Dockerfile.

MINECRAFT_STARTUP_JAR

When packaging a modpack, you will need to start the server using a different jar file. To specify the startup jar, set the MINECRAFT_STARTUP_JAR variable in your Dockerfile.

MINECRAFT_OPTS

Some modpacks have their own recommended JVM settings. You can include them via the MINECRAFT_OPTS variable in your Dockerfile.

Supported Docker versions

This image has been tested on Docker version 1.1.1.

Feedback

Feel free to open a Github issue.

If you wish to contribute, you may open a pull request.