[](https://github.com/itzg/docker-minecraft-server/actions)
> If you plan on running a server for a longer amount of time it is highly recommended using a management layer such as [Docker Compose](#using-docker-compose) or [Kubernetes](#deployment-templates-and-examples) to allow for incremental reconfiguration and image upgrades.
By default, the container will download the latest version of the "vanilla" [Minecraft: Java Edition server](https://www.minecraft.net/en-us/download/server) provided by Mojang. The [`VERSION`](#versions) and the [`TYPE`](#server-types) can be configured to create many variations of desired Minecraft server.
**Please ensure you have pulled the latest image** since [all official mitigations](https://www.minecraft.net/en-us/article/important-message--security-vulnerability-java-edition) are automatically applied by the container startup process.
If rcon is disabled you can send commands by passing them as arguments to the packaged `mc-send-to-console` script. For example, a player can be op'ed in the container `mc` with:
```shell
docker exec mc mc-send-to-console op player
| |
+- container name +- Minecraft commands start here
> NOTE: The container path `/data` is pre-declared as a volume, so if you do nothing then it will be allocated as an anonymous volume. As such, it is subject to removal when the container is removed.
In most cases the easiest way to persist and work with the minecraft data files is to use the [volume mounting](https://docs.docker.com/storage/volumes/) `-v` argument to map a directory on your host machine to the container's `/data` directory. In the following example, the path `/home/user/minecraft-data`**must be** a directory on your host machine:
When attached in this way you can stop the server, edit the configuration under your attached directory and start the server again to pick up the new configuration.
With Docker Compose, setting up a host attached directory is even easier since relative paths can be configured. For example, with the following `docker-compose.yml` Docker will automatically create/attach the relative directory `minecraft-data` to the container.
> NOTE: if you have SELinux enabled, then you might need to add `:Z` to the end of volume mount specifications, [as described here](https://prefetch.net/blog/2017/09/30/using-docker-volumes-on-selinux-enabled-servers/).
### Converting anonymous `/data` volume to named volume
If you had used the commands in the first section, without the `-v` volume attachment, then an anonymous data volume was created by Docker. You can later bring over that content to a named or host attached volume using the following procedure.
> In this example, it is assumed the original container was given a `--name` of "mc", so change the container identifier accordingly.
When using the image `itzg/minecraft-server` without a tag, the `latest` image tag is implied from the table below. To use a different version of Java, please use an alternate tag to run your Minecraft server container.
> Keep in mind that some versions of Minecraft server, such as Forge before 1.17, can't work on the newest versions of Java. Instead, one of the Java 8 images should be used. Also, FORGE doesn't support openj9 JVM implementation.
> Some versions of vanilla Minecraft, such as 1.10, also do not run correctly with Java 17. If in doubt, use `java8-multiarch` for any version less than 1.17.
This image contains [mc-monitor](https://github.com/itzg/mc-monitor) and uses its `status` command to continually check on the container's. That can be observed from the `STATUS` column of `docker ps`
There's actually a wrapper script called `mc-health` that takes care of calling `mc-monitor status` with the correct arguments. If needing to customize the health checks parameters, such as in a compose file, then use something like the following in the service declaration:
Some orchestration systems, such as Portainer, don't allow for disabling the default `HEALTHCHECK` declared by this image. In those cases you can approximate the disabling of healthchecks by setting the environment variable `DISABLE_HEALTHCHECK` to `true`.
The [examples directory](https://github.com/itzg/docker-minecraft-server/tree/master/examples) also provides examples of deploying the [itzg/minecraft-server](https://hub.docker.com/r/itzg/minecraft-server/) Docker image.
If you're looking for a simple way to deploy this to the Amazon Web Services Cloud, check out the [Minecraft Server Deployment (CloudFormation) repository](https://github.com/vatertime/minecraft-spot-pricing). This repository contains a CloudFormation template that will get you up and running in AWS in a matter of minutes. Optionally it uses Spot Pricing so the server is very cheap, and you can easily turn it off when not in use.
To troubleshoot the container initialization, such as when server files are pre-downloaded, set the environment variable `DEBUG` to `true`. The container logs will include **much more** output, and it is highly recommended including that output when reporting any [issues](https://github.com/itzg/docker-minecraft-server/issues).
To troubleshoot just the command-line used to start the Minecraft server, set the environment variable `DEBUG_EXEC` to `true`.
To troubleshoot any issues with memory allocation reported by the JVM, set the environment variable `DEBUG_MEMORY` to `true`.
The overall version is specified by `VERSION`, [as described in the section above](#versions) and will run the recommended Forge version by default. You can also choose to run a specific Forge version with `FORGE_VERSION`, such as `-e FORGE_VERSION=14.23.5.2854`.
> If an error occurred while installing Forge, it might be possible to resolve by temporarily setting `FORGE_FORCE_REINSTALL` to "true". Be sure to remove that variable after successfully starting the server.
By default, the container will install the latest [fabric server launcher](https://fabricmc.net/use/server/), using the latest [fabric-loader](https://fabricmc.net/wiki/documentation:fabric_loader) against the minecraft version you have defined with `VERSION` (defaulting to the latest vanilla release of the game).
A specific loader or launcher version other than the latest can be requested using `FABRIC_LOADER_VERSION` and `FABRIC_LAUNCHER_VERSION` respectively, such as:
> If you wish to use an alternative launcher you can:
> * Provide the path to a custom launcher jar available to the container with `FABRIC_LAUNCHER`, relative to `/data` (such as `-e FABRIC_LAUNCHER=fabric-server-custom.jar`)
> * Provide the URL to a custom launcher jar with `FABRIC_LAUNCHER_URL` (such as `-e FABRIC_LAUNCHER_URL=http://HOST/fabric-server-custom.jar`)
See the [Working with mods and plugins](#working-with-mods-and-plugins) section to set up Fabric mods and configuration.
Enable [Quilt server](https://quiltmc.org/) mode by adding a `-e TYPE=QUILT` to your command-line.
```
docker run -d -v /path/on/host:/data \
-e TYPE=QUILT \
-p 25565:25565 -e EULA=TRUE --name mc itzg/minecraft-server
```
By default, the container will install the latest [quilt server launcher](https://quiltmc.org/install/server/), using the latest [quilt-installer](https://github.com/QuiltMC/quilt-installer) against the minecraft version you have defined with `VERSION` (defaulting to the latest vanilla release of the game).
A specific loader or installer version other than the latest can be requested using `QUILT_LOADER_VERSION` and `QUILT_INSTALLER_VERSION` respectively, such as:
```
docker run -d -v /path/on/host:/data ... \
-e TYPE=QUILT \
-e QUILT_LOADER_VERSION=0.16.0 \
-e QUILT_INSTALLER_VERSION=0.4.1
```
> If you wish to use an alternative launcher you can:
> * Provide the path to a custom launcher jar available to the container with `QUILT_LAUNCHER`, relative to `/data` (such as `-e QUILT_LAUNCHER=quilt-server-custom.jar`)
> * Provide the URL to a custom launcher jar with `QUILT_LAUNCHER_URL` (such as `-e QUILT_LAUNCHER_URL=http://HOST/quilt-server-custom.jar`)
See the [Working with mods and plugins](#working-with-mods-and-plugins) section to set up Quilt mods and configuration.
Plugins can either be managed within the `plugins` subdirectory of the [data directory](#data-directory) or you can also [attach a `/plugins` volume](#optional-plugins-mods-and-config-attach-points). If you add plugins while the container is running, you'll need to restart it to pick those up.
> NOTE some of the `VERSION` values are not as intuitive as you would think, so make sure to click into the version entry to find the **exact** version needed for the download. For example, "1.8" is not sufficient since their download naming expects `1.8-R0.1-SNAPSHOT-latest` exactly.
By default, the container will run the latest build of [Paper server](https://papermc.io/downloads) but you can also choose to run a specific build with `-e PAPERBUILD=205`.
If you have attached a host directory to the `/data` volume, then you can install plugins via the `plugins` subdirectory. You can also [attach a `/plugins` volume](#optional-plugins-mods-and-config-attach-points). If you add plugins while the container is running, you'll need to restart it to pick those up.
A [Pufferfish](https://github.com/pufferfish-gg/Pufferfish) server, which is "a highly optimized Paper fork designed for large servers requiring both maximum performance, stability, and "enterprise" features."
A [Purpur](https://purpurmc.org/) server, which is "a drop-in replacement for Paper servers designed for configurability and new, fun, exciting gameplay features."
[Canyon](https://github.com/canyonmodded/canyon) is a fork of CraftBukkit for Minecraft Beta 1.7.3. It includes multiple enhancements whilst also retaining compatibility with old Bukkit plugins and mods as much as possible.
> **NOTE** only `VERSION=b1.7.3` is supported. Since that version pre-dates the health check mechanism used by this image, that will need to be disabled by setting `DISABLE_HEALTHCHECK=true`.
Beware that current [Sponge](https://www.spongepowered.org) `STABLE` versions for Minecraft 1.12 require using [the Java 8 tag](#running-minecraft-server-on-different-java-version):
A [Limbo](https://github.com/LOOHP/Limbo) server can be run by setting `TYPE` to `LIMBO`.
Configuration options with defaults:
-`LIMBO_BUILD`=LATEST
The `VERSION` will be ignored so locate the appropriate value from [here](https://ci.loohpjames.com/job/Limbo/) to match the version expected by clients.
> NOTE: instead of using format codes in the MOTD, Limbo requires [JSON chat content](https://minecraft.fandom.com/wiki/Raw_JSON_text_format#Java_Edition). If a plain string is provided, which is the default, then it gets converted into the required JSON structure.
[Feed the Beast application](https://www.feed-the-beast.com/) modpacks are supported by using `-e TYPE=FTBA` (**note** the "A" at the end of the type). This server type will automatically take care of downloading and installing the modpack and appropriate version of Forge, so the `VERSION` does not need to be specified.
-`FTB_MODPACK_ID`: **required**, the numerical ID of the modpack to install. The ID can be located by [finding the modpack](https://www.feed-the-beast.com/modpack) and locating the ID in this part of the URL:
-`FTB_MODPACK_VERSION_ID`: optional, the numerical ID of the version to install. If not specified, the latest version will be installed. The "Version ID" can be obtained by hovering over a server file entry and grabbing [this ID in the URL](docs/ftba-version-id-popup.png).
If a specific `FTB_MODPACK_VERSION_ID` was not specified, simply restart the container to pick up the newest modpack version. If using a specific version ID, recreate the container with the new version ID.
### Example
The following example runs the latest version of [FTB Presents Direwolf20 1.12](https://ftb.neptunepowered.org/pack/ftb-presents-direwolf20-1-12/):
By default, CurseForge modpacks are expanded into the sub-directory `/data/FeedTheBeast` and executed from there. (The default location was chosen for legacy reasons, when Curse and FTB were maintained together.)
The directory can be changed by setting `CF_BASE_DIR`, such as `-e CF_BASE_DIR=/data`.
Some modpacks have buggy or overly complex start scripts. You can avoid using the bundled start script and use this image's standard server-starting logic by adding `-e USE_MODPACK_START_SCRIPT=false`.
If your server's modpack fails to load with an error [like this](https://support.feed-the-beast.com/t/cant-start-crashlanding-server-unable-to-launch-forgemodloader/6028/2):
unable to launch forgemodloader
then you apply a workaround by adding this to the run invocation:
[packwiz](https://packwiz.infra.link/) is a CLI tool for maintaining and providing modpack definitions, with support for both CurseForge and Modrinth as sources. See the [packwiz tutorial](https://packwiz.infra.link/tutorials/getting-started/) for more information.
To configure server mods using a packwiz modpack, set the `PACKWIZ_URL` environment variable to the location of your `pack.toml` modpack definition:
docker run -d -v /path/on/host:/data -e TYPE=FABRIC \
packwiz modpack defitions are processed before other mod definitions (`MODPACK`, `MODS`, etc.) to allow for additional processing/overrides you may want to perform (in case of mods not available via Modrinth/CurseForge, or you do not maintain the pack).
> packwiz is pre-configured to only download server mods. If client-side mods are downloaded and cause issues, check your pack.toml configuration, and make sure any client-only mods are not set to `"both"`, but rather `"client"` for the side configuration item.
: contents are synchronized into `/data/plugins` for Bukkit related server types. Set `SYNC_SKIP_NEWER_IN_DESTINATION=false` if you want files from `/plugins` to take precedence over newer files in `/data/plugins`.
: contents are synchronized into `/data/config` by default, but can be changed with `COPY_CONFIG_DEST`. For example, `-v ./config:/config -e COPY_CONFIG_DEST=/data` will allow you to copy over files like `bukkit.yml` and so on directly into the server directory. Set `SYNC_SKIP_NEWER_IN_DESTINATION=false` if you want files from `/config` to take precedence over newer files in `/data/config`.
By default, the [environment variable processing](#replacing-variables-inside-configs) is performed on synchronized files that match the expected suffixes in `REPLACE_ENV_SUFFIXES` (by default "yml,yaml,txt,cfg,conf,properties,hjson,json,tml,toml") and are not excluded by `REPLACE_ENV_VARIABLES_EXCLUDES` and `REPLACE_ENV_VARIABLES_EXCLUDE_PATHS`. This processing can be disabled by setting `REPLACE_ENV_DURING_SYNC` to `false`.
If you want old mods/plugins to be removed before the content is brought over from those attach points, then add `-e REMOVE_OLD_MODS=TRUE`. You can fine tune the removal process by specifying the `REMOVE_OLD_MODS_INCLUDE` and `REMOVE_OLD_MODS_EXCLUDE` variables, which are comma separated lists of file glob patterns. If a directory is excluded, then it and all of its contents are excluded. By default, only jars are removed.
You can also specify the `REMOVE_OLD_MODS_DEPTH` (default is 16) variable to only delete files up to a certain level.
For example: `-e REMOVE_OLD_MODS=TRUE -e REMOVE_OLD_MODS_INCLUDE="*.jar" -e REMOVE_OLD_MODS_DEPTH=1` will remove all old jar files that are directly inside the `plugins/` or `mods/` directory.
These paths work well if you want to have a common set of modules in a separate location, but still have multiple worlds with different server requirements in either persistent volumes or a downloadable archive.
> For more flexibility with mods/plugins preparation, you can declare directories to use in [the `MODS` variable](#downloadable-modplugin-pack-for-forge-fabric-and-bukkit-like-servers)
The `SPIGET_RESOURCES` variable can be set with a comma-separated list of SpigotMC resource IDs to automatically download [SpigotMC resources/plugins](https://www.spigotmc.org/resources/) using [the spiget API](https://spiget.org/). Resources that are zip files will be expanded into the plugins directory and resources that are simply jar files will be moved there.
For example, the following will auto-download the [EssentialsX](https://www.spigotmc.org/resources/essentialsx.9089/) and [Vault](https://www.spigotmc.org/resources/vault.34315/) plugins:
[Modrinth](https://modrinth.com/) is an open source modding platform with a clean, easy to use website for finding [Fabric and Forge mods](https://modrinth.com/mods). At startup, the container will automatically locate and download the newest versions of mod files that correspond to the `TYPE` and `VERSION` in use. Older file versions downloaded previously will automatically be cleaned up.
- **MODRINTH_PROJECTS** : comma separated list of project slugs (short name) or IDs. The project ID can be located in the "Technical information" section. The slug is the part of the page URL that follows `/mod/`:
```
https://modrinth.com/mod/fabric-api
----------
|
+-- project slug
```
- **MODRINTH_DOWNLOAD_OPTIONAL_DEPENDENCIES**=true : required dependencies of the project will _always_ be downloaded and optional dependencies can also be downloaded by setting this to `true`
- **MODRINTH_ALLOWED_VERSION_TYPE**=release : the version type is used to determine the newest version to use from each project. The allowed values are `release`, `beta`, `alpha`.
This is more complicated because you will be pulling/using the latest mod for the release of your game. To get started make sure you have a [CursedForge API Key](https://docs.curseforge.com/#getting-started). Then use the environmental parameters in your docker build.
*`MODS_FORGEAPI_IGNORE_GAMETYPE` - Default is False, Allows for filtering mods on family type: FORGE, FABRIC, and BUKKIT. (Does not filter for Vanilla or custom)
To install all the server content (jars, mods, plugins, configs, etc.) from a zip or tgz file, then set `GENERIC_PACK` to the container path or URL of the archive file. This can also be used to apply a CurseForge modpack that is missing a server start script and/or Forge installer.
If multiple generic packs need to be applied together, set `GENERIC_PACKS` instead, with a comma separated list of archive file paths and/or URLs to files.
To avoid repetition, each entry will be prefixed by the value of `GENERIC_PACKS_PREFIX` and suffixed by the value of `GENERIC_PACKS_SUFFIX`, both of which are optional. For example, the following variables
```
GENERIC_PACKS=configs-v9.0.1,mods-v4.3.6
GENERIC_PACKS_PREFIX=https://cdn.example.org/
GENERIC_PACKS_SUFFIX=.zip
```
would expand to `https://cdn.example.org/configs-v9.0.1.zip,https://cdn.example.org/mods-v4.3.6.zip`.
If applying large generic packs, the update can be time-consuming. To skip the update set `SKIP_GENERIC_PACK_UPDATE_CHECK` to "true". Conversely, the generic pack(s) can be forced to be applied by setting `FORCE_GENERIC_PACK_UPDATE` to "true".
The most time consuming portion of the generic pack update is generating and comparing the SHA1 checksum. To skip the checksum generation, set `SKIP_GENERIC_PACK_CHECKSUM` to "true.
As an alternative to `MODS`, the variable `MODS_FILE` can be set with the path to a text file listing a mod/plugin URL on each line. For example, the following
-e MODS_FILE=/extras/mods.txt
would load from a file mounted into the container at `/extras/mods.txt`. That file might look like:
Instead of mounting the `/data` volume, you can instead specify the URL of a ZIP or compressed TAR file containing an archived world. It will be searched for a file `level.dat` and the containing subdirectory moved to the directory named by `$LEVEL`. This means that most of the archived Minecraft worlds downloadable from the Internet will already be in the correct format.
**NOTE:** This URL must be accessible from inside the container. Therefore, you should use an IP address or a globally resolvable FQDN, or else the name of a linked container.
The `WORLD` option can also be used to reference a directory, zip file, or compressed tar file that will be used as a source to clone or extract the world directory.
For example, the following would initially clone the world's content from `/worlds/basic`. Also notice in the example that you should use a read-only volume attachment to ensure the clone source remains pristine.
The world will only be downloaded or copied if it doesn't exist already. Set `FORCE_WORLD_COPY=TRUE` to force overwrite the world on every server start.
To set a custom worlds directory for the Multiverse plugin on a baremetal server, you'd pass the `--world-dir` argument after the jar file.
In order to accomplish the same in a containerized server, set the `EXTRA_ARGS` environment variable in your command line or docker compose yaml to the same argument string. For example:
```
docker run -d -e EXTRA_ARGS='--world-dir ./worlds/'
```
`--world-container`, `-W`, and `--universe` are aliases to `--world-dir` and can also be used.
Datapacks can be installed in a similar manner to mods/plugins. There are many environment variables which function in the same way they do for [mods](#working-with-mods-and-plugins):
*`DATAPACKS`: comma-separated list of zip file URL, zip file in container, or directory in container
*`DATAPACKS_FILE`: a text file within the container where each line is a zip file URL, zip file in container, or directory in container
*`REMOVE_OLD_DATAPACKS`: if "true" the datapacks directory is removed of everything matching `REMOVE_OLD_DATAPACKS_INCLUDE`, but excluding `REMOVE_OLD_DATAPACKS_EXCLUDE` no deeper than `REMOVE_OLD_DATAPACKS_DEPTH`
*`REMOVE_OLD_DATAPACKS_DEPTH`: default is 16
*`REMOVE_OLD_DATAPACKS_INCLUDE`: default is `*.zip`
[VanillaTweaks](https://vanillatweaks.net/) datapacks, crafting tweaks, and resource packs can be installed with a share code from the website **OR** a json file to specify packs to download and install. Datapacks and crafting tweaks will be installed into the current world directory specified by `$LEVEL`. As new versions of the packs are retrieved the previous versions will automatically be cleaned up.
By default, the server configuration will be created and set based on the following environment variables, but only the first time the server is started. If the `server.properties` file already exists, the values in them will not be changed.
If you prefer to manually manage the `server.properties` file, set `OVERRIDE_SERVER_PROPERTIES` to "false". Similarly, you can entirely skip the startup script's creation of `server.properties` by setting `SKIP_SERVER_PROPERTIES` to "true".
> NOTE: to clear a server property, set the variable to an empty string, such as `-e RESOURCE_PACK=""`. A variables that maps to a server property that is unset, is ignored and the existing `server.property` is left unchanged.
The section symbol (§) and other unicode characters are automatically converted to allow [formatting codes](https://minecraft.fandom.com/wiki/Formatting_codes) to be used consistently with all server versions. For example,
When either is set, [whitelisting of connecting users](https://minecraft.fandom.com/wiki/Server.properties#white-list) is enabled . If managing the list manually, `ENABLE_WHITELIST` can be set to "true" to set the `white-list` property.
If whitelist configuration already exists, `WHITELIST_FILE` will not be retrieved and any usernames in `WHITELIST` are **added** to the whitelist configuration. You can enforce regeneration of the whitelist on each server startup by setting `OVERRIDE_WHITELIST` to "true". This will delete the whitelist file before processing whitelist configuration.
> If running Minecraft 1.7.5 or earlier, these variables will apply to `white-list.txt`, with 1.7.6 implementing support for `whitelist.json`. Make sure your `WHITELIST_FILE` is in the appropriate format.
To [enforce the whitelist changes immediately](https://minecraft.fandom.com/wiki/Server.properties#enforce-whitelist) when whitelist commands are used , set `ENFORCE_WHITELIST` to "true".
If ops configuration already exists, `OPS_FILE` will not be retrieved and any usernames in `OPS` are **added** to the ops configuration. You can enforce regeneration of the ops configuration on each server startup by setting `OVERRIDE_OPS` to "true". This will delete the ops file before processing ops configuration.
New to [22W42A](https://www.minecraft.net/en-us/article/minecraft-snapshot-22w42a), datapacks with feature flags can be controlled before initial world creation by setting these to a comma separated list of packs:
RCON is **enabled by default** to allow for graceful shut down the server and coordination of save state during backups. RCON can be disabled by setting `ENABLE_RCON` to "false".
The default password is "minecraft" but **change the password before deploying into production** by setting `RCON_PASSWORD`.
**DO NOT MAP THE RCON PORT EXTERNALLY** unless you aware of all the consequences and have set a **secure password** with `RCON_PASSWORD`.
> Mapping ports (`-p` command line or `ports` in compose) outside the container and docker networking needs to be a purposeful choice. Most production Docker deployments do not need any of the Minecraft ports mapped externally from the server itself.
By default, the server listens for RCON on port 25575 within the container. It can be changed with `RCON_PORT` but only do this if you have a very good reason. **DO NOT change `rcon.port` via `server.properties`** or integrations will break.
If set to true, players will be set to spectator mode if they die.
docker run -d -e HARDCORE=false
### Snooper
If set to false, the server will not send data to snoop.minecraft.net server.
docker run -d -e SNOOPER_ENABLED=false
### Max Build Height
The maximum height in which building is allowed.
Terrain may still naturally generate above a low height limit.
docker run -d -e MAX_BUILD_HEIGHT=256
### Max Tick Time
The maximum number of milliseconds a single tick may take before the server watchdog stops the server with the message, A single server tick took 60.00 seconds (should be max 0.05); Considering it to be crashed, server will forcibly shutdown. Once this criteria is met, it calls System.exit(1).
For some of the level types, `GENERATOR_SETTINGS` can be used to further customize the world generation [as described here](https://minecraft.fandom.com/wiki/Server.properties#generator-settings).
You can set a link to a custom resource pack and set it's checksum using the `RESOURCE_PACK` and `RESOURCE_PACK_SHA1` options respectively, the default is blank:
By default, server checks connecting players against Minecraft's account database. If you want to create an offline server or your server is not connected to the internet, you can disable the server to try connecting to minecraft.net to authenticate players with environment variable `ONLINE_MODE`, like this
docker run -d -e ONLINE_MODE=FALSE ...
### Allow flight
Allows users to use flight on your server while in Survival mode, if they have a mod that provides flight installed.
The server name (e.g. for bungeecord) can be set like:
docker run -d -e SERVER_NAME=MyServer ...
### Server port
> **WARNING:** only change this value if you know what you're doing. It is only needed when using host networking and it is rare that host networking should be used. Use `-p` port mappings instead.
If you must, the server port can be set like:
docker run -d -e SERVER_PORT=25566 ...
**however**, be sure to change your port mapping accordingly and be prepared for some features to break.
When the environment variable `REPLACE_ENV_IN_PLACE` is set to `true` (the default), the startup script will go through all files inside the container's `/data` path and replace variables that match the container's environment variables. Variables can instead (or in addition to) be replaced in files sync'ed from `/plugins`, `/mods`, and `/config` by setting `REPLACE_ENV_DURING_SYNC` to `true` (defaults to `false`).
Variables that you want to replace need to be declared inside curly brackets and prefixed with a dollar sign, such as `${CFG_YOUR_VARIABLE}`, which is same as many scripting languages.
You can also change `REPLACE_ENV_VARIABLE_PREFIX`, which defaults to "CFG_", to limit which environment variables are allowed to be used. For example, with "CFG_" as the prefix, the variable `${CFG_DB_HOST}` would be subsituted, but not `${DB_HOST}`.
If you want to use a file's content for value, such as when using secrets mounted as files, declare the placeholder named like normal in the file and declare an environment variable named the same but with the suffix `_FILE`.
For example, a `my.cnf` file could contain:
```
[client]
password = ${CFG_DB_PASSWORD}
```
...a secret declared in the compose file with:
```yaml
secrets:
db_password:
external: true
```
...and finally the environment variable would be named with a `_FILE` suffix and point to the mounted secret:
JSON path based patches can be applied to one or more existing files by setting the variable `PATCH_DEFINITIONS` to the path of a directory that contains one or more [patch definition json files](https://github.com/itzg/mc-image-helper#patchdefinition) or a [patch set json file](https://github.com/itzg/mc-image-helper#patchset).
Variable placeholders in the patch values can be restricted by setting `REPLACE_ENV_VARIABLE_PREFIX`, which defaults to "CFG_".
The following example shows a patch-set file were various fields in the `paper.yaml` configuration file can be modified and added:
> **NOTES:** Only JSON and Yaml files can be patched at this time. TOML support is planned to be added next. Removal of comments and other cosmetic changes will occur when patched files are processed.
To let the JVM calculate the heap size from the container declared memory limit, unset `MEMORY` with an empty value, such as `-e MEMORY=""`. By default, the JVM will use 25% of the container memory limit as the heap limit; however, as an example the following would tell the JVM to use 75% of the container limit of 2GB of memory:
> The settings above only set the Java **heap** limits. Memory resource requests and limits on the overall container should also account for non-heap memory usage. An extra 25% is [a general best practice](https://dzone.com/articles/best-practices-java-memory-arguments-for-container).
environment variable. The JVM requires `-XX` options to precede `-X` options, so those can be declared in `JVM_XX_OPTS`. Both variables are space-delimited, raw JVM arguments.
For some cases, if e.g. after removing mods, it could be necessary to startup minecraft with an additional `-D` parameter like `-Dfml.queryResult=confirm`. To address this you can use the environment variable `JVM_DD_OPTS`, which builds the params from a given list of values separated by space, but without the `-D` prefix. To make things running under systems (e.g. Plesk), which doesn't allow `=` inside values, a `:` (colon) could be used instead. The upper example would look like this:
Options that would usually be passed to the jar file (those which are written after the filename) can be passed via the `EXTRA_ARGS` environment variable.
See [Custom worlds directory path](#custom-worlds-directory-path) for an example.
To allow time for players to finish what they're doing during a graceful server shutdown, set `STOP_SERVER_ANNOUNCE_DELAY` to a number of seconds to delay after an announcement is posted by the server.
> **NOTE** be sure to adjust Docker's shutdown timeout accordingly, such as using [the -t option on docker-compose down](https://docs.docker.com/compose/reference/down/).
To enable remote JMX, such as for profiling with VisualVM or JMC, add the environment variable `ENABLE_JMX=true`, set `JMX_HOST` to the IP/host running the Docker container, and add a port forwarding of TCP port 7091, such as:
[Aikar has done some research](https://aikar.co/2018/07/02/tuning-the-jvm-g1gc-garbage-collector-flags-for-minecraft/) into finding the optimal JVM flags for GC tuning, which becomes more important as more users are connected concurrently. The set of flags documented there can be added using
When the container is signalled to stop, the Minecraft process wrapper will attempt to send a "stop" command via RCON or console and waits for the process to gracefully finish. By default it waits 60 seconds, but that duration can be configured by setting the environment variable `STOP_DURATION` to the number of seconds.
If you are using a host-attached data directory, then you can have the image setup the Minecraft server files and stop prior to launching the server process by setting `SETUP_ONLY` to `true`.
RCON commands can be configured to execute when the server starts, a client connects, or a client disconnects.
> When declaring several commands within a compose file environment variable, it's easiest to use YAML's `|-` [block style indicator](https://yaml-multiline.info/).
There are various bug reports on [Mojang](https://bugs.mojang.com) about high CPU usage of servers with newer versions, even with few or no clients connected (e.g. [this one](https://bugs.mojang.com/browse/MC-149018), in fact the functionality is based on [this comment in the thread](https://bugs.mojang.com/browse/MC-149018?focusedCommentId=593606&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-593606)).
An autopause functionality has been added to this image to monitor whether clients are connected to the server. If for a specified time no client is connected, the Java process is stopped. When knocking on the server port (e.g. by the ingame Multiplayer server overview), the process is resumed. The experience for the client does not change.
Of course, even loaded chunks are not ticked when the process is stopped.
**You must greatly increase or disable max-tick-time watchdog functionality.** From the server's point of view, the pausing causes a single tick to take as long as the process is stopped, so the server watchdog might intervene after the process is continued, possibly forcing a container restart. To prevent this, ensure that the `max-tick-time` in the `server.properties` file is set to a very large value or -1 to disable it entirely, which is highly recommended. That can be set with `MAX_TICK_TIME` as described in [the section below](#max-tick-time).
> **NOTE:** Non-vanilla versions might have their own configuration file, you might have to disable their watchdogs separately. For PaperMC servers, you need to send the JVM flag `-Ddisable.watchdog=true`, this can be done with the docker env variable `-e JVM_DD_OPTS=disable.watchdog:true`
On startup the `server.properties` file is checked and, if applicable, a warning is printed to the terminal. When the server is created (no data available in the persistent directory), the properties file is created with the Watchdog disabled.
The utility used to wake the server (`knock(d)`) works at network interface level. So the correct interface has to be set using the `AUTOPAUSE_KNOCK_INTERFACE` variable when using non-default networking environments (e.g. host-networking, Portainer oder NAS solutions). See the description of the variable below.
A file called `.paused` is created in `/data` directory when the server is paused and removed when the server is resumed. Other services may check for this file's existence before waking the server.
> When configuring kubernetes readiness/liveness health checks with auto-pause enabled, be sure to reference the `mc-health` wrapper script rather than `mc-status` directly.
describes the time between server start and the pausing of the process, when no client connects inbetween (read as timeout initialized)
*`AUTOPAUSE_TIMEOUT_KN`, default `120` (seconds)
describes the time between knocking of the port (e.g. by the main menu ping) and the pausing of the process, when no client connects inbetween (read as timeout knocked)
*`AUTOPAUSE_PERIOD`, default `10` (seconds)
describes period of the daemonized state machine, that handles the pausing of the process (resuming is done independently)
*`AUTOPAUSE_KNOCK_INTERFACE`, default `eth0`
<br>Describes the interface passed to the `knockd` daemon. If the default interface does not work, run the `ifconfig` command inside the container and derive the interface receiving the incoming connection from its output. The passed interface must exist inside the container. Using the loopback interface (`lo`) does likely not yield the desired results.
An option to stop the server after a specified time has been added for niche applications (e.g. billing saving on AWS Fargate). The function is incompatible with the Autopause functionality, as they basically cancel out each other.
Note that the docker container variables have to be set accordingly (restart policy set to "no") and that the container has to be manually restarted.
A starting, example compose file has been provided in [examples/docker-compose-autostop.yml](examples/docker-compose-autostop.yml).
Enable the Autostop functionality by setting:
```
-e ENABLE_AUTOSTOP=TRUE
```
The following environment variables define the behaviour of auto-stopping:
*`AUTOSTOP_TIMEOUT_EST`, default `3600` (seconds)
describes the time between the last client disconnect and the stopping of the server (read as timeout established)
To run this image on a RaspberryPi 3 B+, 4, or newer, use any of the image tags [list in the Java version section](#running-minecraft-server-on-different-java-version) that specify `armv7` for the architecture, which includes `itzg/minecraft-server:latest`.
> If experiencing issues such as "sleep: cannot read realtime clock: Operation not permitted", ensure `libseccomp` is up to date on your host. In some cases adding `:Z` flag to the `/data` mount may be needed, [but use cautiously](https://docs.docker.com/storage/bind-mounts/#configure-the-selinux-label).
