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Fix Mod-Related Server Crashes

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If your modpack is not starting up or if it’s crashing, you may be experiencing a bug with the program code of a mod. This article is a work in progress. Contact support if you need clarification with reading the crash report.

Determine the Cause of the Crash

Check the console for an error message. Additionally, check the crash-reports folder for crash report files. You can access the crash-reports folder by clicking on Files in Command Center. In the error messages, you can usually make out the name of the mod that is causing the issue.

For example:

java.lang.ArrayIndexOutOfBoundsException:-1
    at thermalexpansion.part.conduit.item.ConduitItem.doRouteItem(ConduitItem.java:529)
    at thermalexpansion.part.conduit.item.ConduitItem.routeItem(ConduitItem.java:518)
    at thermalexpansion.part.conduit.item.ConduitItem.popStuffedItems(ConduitItem.java:460)
    at thermalexpansion.part.conduit.item.ConduitItem.doOutput(ConduitItem.java:107)
    at thermalexpansion.part.conduit.item.GridItem.doGridUpdate(GridItem.java:53)
    at thermalexpansion.part.conduit.GridTickHandler.tickEnd(GridTickHandler.java:74)
    at cpw.mods.fml.common.SingleIntervalHandler.tickEnd(SingleIntervalHandler.java:34)
    at cpw.mods.fml.common.FMLCommonHandler.tickEnd(FMLCommonHandler.java:141)
    at cpw.mods.fml.common.FMLCommonHandler.onPostServerTick(FMLCommonHandler.java:274)
    at net.minecraft.server.MinecraftServer.func\_71217\_p(MinecraftServer.java:622)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
    at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)

In the above example, ThermalExpansion is the issue. It’s something related to conduits. Remember the name of the mod in the error messages.

It may be more difficult to figure out what mod is causing a problem. The above example, like most cases, should make it fairly obvious. If you can’t figure out what the cause of the crash is, contact support.

Remove Erroring Entities and TileEntities

Forge has a built in configuration setting to remove erroring entities and remove erroring tileentities problems for you on the fly. For example, if you have an entity that is causing your server to crash, such as a modded creature that isn’t working properly, this setting can delete the entity when the server loads instead of crashing.

Don’t leave this setting on. It can have unforeseen consequences and delete things unexpectedly. It’s only meant to fix small issues. Leaving it on could cause the server to delete anything that has an issue even if it wouldn’t have crashed the server.

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Backup, Backup, Backup

Always backup your server using the Backups link on the left of Command Center before making changes to the files.

  1. Login to Command Center.
  2. From the server list, find the server that you wish to modify, and click the Manage button on the right.
  3. From the server you selected, click on the Files tab.
  4. Navigate to the config listed below and open it.
    1. Forge versions below 1.18: /config/forge.cfg
    2. Forge versions above 1.18: /YOURWORLDNAME/serverconfig/forge-server.toml
    3. Neoforge: /config/neoforge-server.toml
  5. Find and set these options to true:
#Set this to true to remove any BlockEntity that throws an error in its update method instead of closing the server and reporting a crash log. BE WARNED THIS COULD SCREW UP EVERYTHING USE SPARINGLY WE ARE NOT RESPONSIBLE FOR DAMAGES.
removeErroringBlockEntities = false

#Set this to true to remove any Entity (Note: Does not include BlockEntities) that throws an error in its tick method instead of closing the server and reporting a crash log. BE WARNED THIS COULD SCREW UP EVERYTHING USE SPARINGLY WE ARE NOT RESPONSIBLE FOR DAMAGES.
removeErroringEntities = false

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For older versions of Forge, the line removeErroringBlockEntities may be labeled removeErroringTileEntities instead. The function is the same.

  1. Save the file and restart your server.

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This will only remove entities in loaded chunks. You may need to log in or travel to effected chunks.

  1. When you’re done, make sure to set both settings back to false and restart your server.

Disable and Re-enable the Problematic Mod

Disabling mods has the potential to delete their mod data from your world such as blocks, items, mobs, or anything else the mod may add to the game. Sometimes, disabling a mod can help resolve a problem, but keep this in mind. We recommend backing up your map before you do this. You can backup your map by clicking on Vault on the left side of Command Center under the gear icon.

Disable the Mod

  1. Stop your server.

  2. Login to your server SFTP and navigate to the folder of the affected game.

  3. Find the name of the affected mod. For example, ThermalExpansion-3.0.0.b10a.jar.

  4. Drag it up one folder into the root of the game folder.

  5. Start your server and then stop it.

    • In some cases, your server will not start up again, as there are dependencies that require the mod that you just removed. In such case, check the console for the names of the mods and remove them as well. Restart each time and make sure your server starts up without error. For example, if you remove ComputerCraft, you’ll also need to remove OpenCCSensors and OpenPeriperhal.

Re-enable the Mod

  1. Drag the affected mod in the root of the game folder back into the mods folder.
  2. Start your server.
  3. Login and check. If your server no longer crashes, then you’re all set. Otherwise, move on to the next part.

Remove the Affected Items

  1. With the mod disabled, login to your server.
  2. Remove the affected blocks, items, entities, etc. Often, a crash report will have the exact coordinates of the affected items.
  3. Re-enable the mod.

Rollback Your Map

If none of the aforementioned options work, rollback your map to before the error started happening.

Updated 2 months ago