Ok I'm setting up a Minecraft vanilla server (i.e. Mojang server, not Bukkit) with Red Power 2, Industrial Craft 2 and Build Craft 2.2 Red Power and Industrial Craft work together nicely. However, after installing the BuildCraft mod, I get this server error:

java.lang.RuntimeException: RedPowerCore: BlockID 148 occupied by buildcraft.transport.LegacyBlock, autoAssign is disabled.
    at forge.MinecraftForge.killMinecraft(MinecraftForge.java:483)
    at eloraam.core.Config.getBlockID(Config.java:114)
    at RedPowerControl.initialize(RedPowerControl.java:21)
    at mod_RedPowerControl.initialize(mod_RedPowerControl.java:37)
    at mod_RedPowerControl.modsLoaded(mod_RedPowerControl.java:18)
    at cpw.mods.fml.server.ModLoaderModContainer.postInit(ModLoaderModContainer.java:277)
    at cpw.mods.fml.common.Loader.postModInit(Loader.java:236)
    at cpw.mods.fml.common.Loader.initializeMods(Loader.java:540)
    at cpw.mods.fml.server.FMLServerHandler.onLoadComplete(FMLServerHandler.java:127)
    at net.minecraft.server.MinecraftServer.s(MinecraftServer.java:203)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:411)
    at dn.run(SourceFile:492)

How do I go about resolving this ID block conflict? Is there a good way to do this or a bad way I should avoid? Is solving this a case by case basis? (i.e. different depending on mods) or is there a file I edit every time to fix this?

Thanks in advance.

  • I've not looked at the code for any mods before, but I guess you could write a script to search through each mod and change the IDs to whatever you want for each block? It would have to match your client too.
    – Ric
    May 21, 2012 at 8:10
  • java.lang.RuntimeException: RedPowerCore: BlockID 148 occupied by buildcraft.transport.LegacyBlock, autoAssign is disabled There must be a function somewhere or a parameter which is called autoAssign, you should activate that. (I suppose)
    – Depado
    May 22, 2012 at 7:43
  • @Depado RedPower has a feature that autoAssigns conflicting block IDs. It resolved a lot of my issues but I'm still having problems getting RailCraft to work with the other mods and quite a few other mods as well. May 24, 2012 at 17:14
  • Well all I can see is that that autoAssign is disabled, maybe when you installed RailCraft it has disabled that function ? You should try to see the configurations of these mods or maybe directly their java code to modify the blocks ID (I don't know much about block ID, but I know that you can solve it with java)
    – Depado
    May 25, 2012 at 7:08

5 Answers 5


Let me take the time to point you to the tekkit mod pack which has not just those mods but much much more (if you don't want the extras, its not like you have to use them).

You can find it here. Just install the launcher and select the modpack you want (tekkit). After that, go back to the website and go to the tekkit tab and download the server.

I know it's a modified version of bukkit, but you don't have to install plugins. Then if you decide one day you want an auto back-up plugin you'll already be on bukkit.

  • I know it's not EXACTLY what you wanted but I think it should help
    – Lysol
    May 26, 2012 at 14:18
  • thanks for this post. I am aware of tekkit and its pretty cool. Do you know if its possible to run tekkit with specific mods and have some turned off? I don't like everything that comes with it and just want a particular set of mods. +1 for the post because its helpful and I think other people may find this to be a quick answer to their problems, but this isn't the answer I'm looking for. May 29, 2012 at 8:44
  • I don't believe it is, sorry :( but why don't you want the other mods? you don't have to use them and you find a mod you really like, such as ComputerCraft.
    – Lysol
    May 29, 2012 at 14:37
  • ComputerCraft isn't needed now because RP2 has something similar (and more superior). Mo' creatures for instance. I've used it and I like its SO MANY mobs every where. Also, if I'm running a server, I'd like to have it as light weight as possible. May 29, 2012 at 22:59
  • 1
    @DJTripleThreat I think it should be sufficient to delete the unwanted mods from %appdata%\.techniclauncher\tekkitlite\mods and turning the launcher's update off. Alternatively, have a look at technicpack.net/custom-zip-build-your-own-private-modpacks, maybe that helps somehow
    – Zommuter
    Feb 17, 2013 at 1:33

Sequential IDs

Many mods expect their block IDs to be sequential. So, when resolving block ID conflicts via config files with sequential IDs, always make sure that you move all the IDs together to maintain their original sequence.

"Low" and "high" IDs

Minecraft uses block IDs 0-255 for blocks that appear during world generation. Block IDs above 255 can't be placed during chunk generation. When resolving block IDs, make sure IDs 255 and below stay in that range and make sure to not use IDs below 255 for blocks that don't need low block IDs; there aren't enough of them to waste on blocks that don't need them.

IDs stay in the save files

Always change IDs before world generation. The save file stores the ID of blocks and nothing else that ties them to the "right" block. So if you change the block ID of Basalt (from RP2) and try to play in an existing world, all your old Basalt blocks will suddenly be something else – whatever it is you gave that ID to.


The easiest way is to get NEI (Not Enough Items). After you have it installed, open your inventory and click options. Then go to Block/Item ID Options, and then click dump ID map now. It will then say where it saved the file. Find it and then open it. It will then show the used and unused IDs. You can use this to find IDs that you can use. Next, find the config folder in your Minecraft root directory. In the config, look for file for the mod causing the problem. You should then be able to change the IDs (you may have to re-configure the IDs for a different mod if it doesn't let you change IDs). Note that you may have to temporarily remove the mod causing the problems to be able to launch the game to get the ID map.


The 4096 Fix allows you to set certain blocks at different IDs up to a limit of 4096, this should be enough to cover all the mods you have.

Scroll down to the 'tweaks' section to get the server and bukkit versions of this mod.

  • +1 I've used this before but couldn't get it to work with the server. I'm going to try again and see what happens. Jun 1, 2012 at 18:00

The ID Resolver mod for Minecraft Forge seems to do what you want. From the picture, it seems that there are a variety of settings to choose from every time you install a new mod.

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