Unable to launch NeoForge server as "invalid dist DEDICATED_SERVER"

[505e06b2]

Bug description

When launching the latest NeoForge dedicated server with AutoModpack, the server fails to start. When the automodpack jar is removed from mods/, all other mods load as expected

The crash happens on both 4.0.0-beta39 and 4.0.0-beta40 with versions <= 4.0.0-beta38 causing a crash related to ...automodpack-4.0.0-beta38.jar is not a valid mod file

Have attempted to downgrade the NeoForge version, but at least one of the mods in my list depend on NeoForge >= 21.1.209

Steps to reproduce

1. Download latest NeoForge installer for 1.21.1 (currently 21.1.210)
2. java -jar [neoforge-*installer.jar]
3. "Install Server" to empty directory
4. Add latest AutoModpack jar (beta40) to mods/ folder
5. ./run.sh

Expected behavior

AutoModpack is bootstrapped and relevant config directories are created

Actual behavior

AutoModpack fails to bootstrap and server crashes with java.lang.BootstrapMethodError: java.lang.RuntimeException: Attempted to load class net/minecraft/client/Minecraft for invalid dist DEDICATED_SERVER

Relevant logs

Server crash report: crash-2025-10-11_14.46.23-fml.txt

Minecraft & Mod Loader versions

1.21.1 NeoForge 21.1.210

Minecraft launcher

None

Operating system

Debian 14 (Testing)

AutoModpack version

4.0.0-beta40

Other information

My current setup heavily uses symlinks and renames all mods to a standard form of {slug}-{version}.*

Check list

• I have verified that the issue persists in the latest version of the mod.
• I have searched the existing issues and confirmed that this is not a duplicate.
• I have provided all the necessary information to reproduce the issue.
• I have verified that the issue does not occur without the AutoModpack - Ignore if you are reporting a mod conflict issue.

[Skidamek]

Hmm, I can't reproduce the issue. Could you please describe exactly how you are using symlinks, and attach the full server log instead of just the crash log?

[505e06b2]

For the symlink setup, this is the first time I've used it with 1.21.1 NeoForge, but it has worked previously with 1.20.1 Fabric 0.17.2 + AutoModpack 4.0.0-beta38

In this example, /mod-management/ holds the actual jar files, while /minecraft-server/ is where the NeoForge server has been installed:

1. Store mod jar files, separated by usage, in external directory /mod-management/:
   • /mod-management/shared/*.jar - mods which target both client and server
   • /mod-management/client/*.jar - mods which target the client (will be ignored in following steps)
   • /mod-management/server/*.jar - mods which target the server
2. Symlink all jar files from /mod-management/shared/*.jar -> /mod-management/server/*.jar so that it merges the server-exclusive mods with the shared ones all in /mod-management/server/
3. Symlink the folder /mod-management/server/ -> /minecraft-server/mods/ to make the mods/ folder point to all shared and server mods

For visual aid of above, and to correlate with logs:

1. Server root:
   

2. Mods folder:
   

Since the bug report, have been playing on the server and added additional mods which have worked fine for now (but may produce a bit more noise in the logs 😅)

Zipped logs/ and crash-reports/ folders, after clearing old logs: automodpack_crash_neoforge.zip

[Skidamek]

Hmm so for some reason, your server doesn't the load essential AutoModpack preload step... Can you confirm that you can see these two java service loader files inside the automodpack jar?

(i still cant reproduce it...)

[Skidamek]

And what if you place automodpack mod into the standard mods folder without symlink on server?

[505e06b2]

Can confirm that those services exist in the jar file:

Attempted to create a reproducible setup, starting from scratch with a fresh server install:

• No symlinks ✔️
• 1 level of symlinks, with mods folder being a "proper" directory, and symlinking /tmp/mods/automodpack-4.0.0-beta40.jar -> mods/automodpack-4.0.0-beta40.jar ✔️
• 2 levels of symlinks, same as above, but also symlinking /tmp/source_dir/automodpack-4.0.0-beta40.jar -> /tmp/mods/automodpack-4.0.0-beta40.jar ✔️
• 3 levels of symlinks, same as above, plus linking /tmp/mods -> mods/ ❌

The solution for the setup I have now seems to be to symlink the mod files into the proper mods/ folder in run.sh
I will note that a similar solution was also how I'd previously solved creating the client modpack (host-modpack/main/mods/*.jar) on Fabric, but will now use this for both the server and client sides

Cheers for your time, happy to have this issue closed 👌

[Skidamek]

so its resolved? not sure what and how could i fix things there... i assume the 3 level symlinks just fail to work, right?

[505e06b2]

It's resolved as in a more than reasonable workaround has been found - the 3 level symlinks just fail as you say
Since the issue looks to be at the filesystem level, it's a bit of a weird one since we'd need the Java runtime to behave

If it's likely for this to be an edge-case (most users are likely on Windows or have a completely isolated server box), it's probably worth focussing effort elsewhere?