1.8.9 FORGE

[torstenbauer]

Hi guys,

maybe someone would be so kind to help me. I try to make my son happy with the setup of his own small minecraft server. I'm not really used to minecraft myself, nor to docker - but quiet confident with linux skills.

I downloaded the container, installed it and he was able to connect - but now he asked me if I could run version 1.8.9 and install some mods...

First fail - the start of 1.8.9

[init] Running as uid=1000 gid=1000 with /data as 'drwxr-x---. 3 1000 1000 4096 Jul  2 18:51 /data'
[init] Image info: buildtime=2025-06-17T12:48:19.332Z,version=java21,revision=a5643cdeac3c1b3d61dbbba6f1136e04895bf613
[init] Resolving type given FORGE
[mc-image-helper] 18:54:07.443 INFO  : Forge version 11.15.1.1726 for minecraft version 1.8.9 is already installed
[init] Copying any mods from /mods to /data/mods
[init] Copying any configs from /config to /data/config
[mc-image-helper] 18:54:09.214 INFO  : Created/updated 1 property in /data/server.properties
[init] Setting initial memory to 1G and max to 1G
[init] Starting the Minecraft server...
A problem occurred running the Server launcher.java.lang.reflect.InvocationTargetException
        at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(Unknown Source)
        at java.base/java.lang.reflect.Method.invoke(Unknown Source)
        at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.run(ServerLaunchWrapper.java:43)
        at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.main(ServerLaunchWrapper.java:12)
Caused by: java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap')
        at net.minecraft.launchwrapper.Launch.<init>(Launch.java:34)
        at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
        ... 4 more
2025-07-02T18:54:09.330Z        WARN    mc-server-runner        Minecraft server failed. Inspect logs above for errors that indicate cause. DO NOT report this line as an error.        {"exitCode": 1}
2025-07-02T18:54:09.330Z        INFO    mc-server-runner        Done

Setup:

Or running:

docker run -it -e EULA=true itzg/minecraft-server:java8-multiarch

ends in:

[init] Running as uid=1000 gid=1000 with /data as 'drwxr-xr-x. 2 1000 1000 4096 Jun 29 00:35 /data'
[init] Image info: buildtime=2025-06-29T00:34:35.551Z,version=java8,revision=c700880bbe7fddefa9582764d78c9a2fe570b5da
[init] Resolving type given VANILLA
[init] Resolved version given LATEST into 1.21.7
[init] Downloading 1.21.7 server...
[init] Copying any configs from /config to /data/config
[init] Creating server properties in /data/server.properties
[init] Disabling whitelist functionality
[mc-image-helper] 19:11:19.877 INFO  : Created/updated 4 properties in /data/server.properties
[init] Setting initial memory to 1G and max to 1G
[init] Starting the Minecraft server...
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.UnsupportedClassVersionError: net/minecraft/bundler/Main has been compiled by a more recent version of the Java Runtime (class file version 65.0), this version of the Java Runtime only recognizes class file versions up to 52.0
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:756)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:473)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
        at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:601)
2025-07-02T19:11:19.947Z        WARN    mc-server-runner        Minecraft server failed. Inspect logs above for errors that indicate cause. DO NOT report this line as an error.        {"exitCode": 1}
2025-07-02T19:11:19.947Z        INFO    mc-server-runner        Done

Any directions? And how can I add mods afterwards and "backup" the container once it is running....

Any help greatly appreciated!

Thanks
Torsten

[torstenbauer]

might be found the solution.. still some exceptions but will test it

docker run -it -e TYPE=FORGE -e VERSION=1.8.9 -e EULA=true itzg/minecraft-server:java8-multiarch

[itzg]

Yep switching to the java8 (aliased to the one you used too) image tag was the correct solution for that version of Forge.