- 1 Galacticraft 4: Compatibility notes
- 2 Galacticraft 3: Compatibility with other mods
- 3 Minecraft and Forge versions
- 4 General compatibility notes
- 4.1 Certain powerful blocks not working in another mod - solution: use Player API
- 4.2 Any other mods with energy and pipe connections
- 4.3 Code in other mods which looks for 'air' blocks
- 4.4 Sealing blocks from other mods
- 4.5 Ores from other mods not generating on planets
- 4.6 Mods which use Global IDs for their entities
- 5 Notes on some specific mods in Minecraft 1.7.10 (including fixable issues)
- 5.1 Optifine
- 5.2 Mekanism
- 5.3 Tinker's Construct
- 5.4 IC2 (IndustrialCraft2)
- 5.5 Buildcraft
- 5.6 Smart Moving
- 5.7 Animated Player
- 5.8 RenderDecorator and VoxelPlayer
- 5.9 RenderPlayerAPIEnhancer
- 5.10 EnviroMine
- 5.11 Sync
- 5.12 Ex Nihilo
- 5.13 Mariculture
- 5.14 GregTech
- 5.15 Extra Utilities
- 5.16 Multiverse
- 5.17 Erebus
- 5.18 Custom NPCs
- 5.19 Dynamic Lights
- 5.20 Dynamic Surroundings
- 6 Non-fixable issues
- 7 Minor issues
- 8 Issues and bugs in other mods (and how to fix them!)
- 9 For clients running OpenJDK
Galacticraft 4: Compatibility notes
Galacticraft 4 is currently compatible with most other mods. If you come across compatibility issues, please (1) check the latest Galacticraft version as we make compatibility improvements all the time; (2) if there's still a problem in the latest, let us know on Github. Also try installing PlayerAPI mod, that can fix some compatibility issues. (The compatibility notes for Galacticraft 3, below, may also be relevant.)
Player inventory tabs
Custom NPCs In Minecraft 1.10.2 and 1.11.2, please make sure to use the latest (25 May 2017 or later) version of this mod with Galacticraft, older versions had inventory tab overlapping issues.
More Player Models In Minecraft 1.10.2 and 1.11.2, please make sure to use the latest (25 May 2017 or later) version of this mod with Galacticraft, older versions had inventory tab overlapping issues.
TechGuns uses its own inventory tabs which overlap with ours - if this is affecting you, please ask the TechGuns developer to update and use our API for compatibility.
Fixed compatibility issues
Avaritia Infinity Armor and other mods with custom hi-poly armor - please update to Galacticraft 4 build 152 or later, to have the armor drawn correctly on planets
Finder Compass To prevent client disconnects, please update your Galacticraft 4 to build 126.96.36.199 or newer.
JourneyMap If you are using JourneyMap waypoint teleports to travel between different planets, please update your Galacticraft 4 to build 188.8.131.52 or newer.
Forge - mods missing screen If you get a crash with this type of error when you start the game:
java.lang.NoClassDefFoundError: cah (Minecraft 1.10.2 might show
bxl instead of
cah there) it might be Forge trying to give you that brown screen naming the required mods "missing", but crashing instead of showing the screen. To solve this issue, try updating Galacticraft and MicdoodleCore to the latest version.
Known compatibility issues
All Shaders mods - please switch off shaders when you leave the Overworld and travel to other planets - shaders mods cannot understand the dark or differently colored sky on the Moon and other planets.
Advanced Rocketry is a space-themed mod which has made some overlapping content with Galacticraft. If Advanced Rocketry and Galacticraft are installed together, Advanced Rocketry may take over some of the space dimensions, for example you may have some features of Advanced Rocketry's oxygen system or gravity on the Moon instead of Galacticraft's features on the Moon. For example, players have complained they can't breath on the Moon when they are wearing Oxygen Mask, Oxygen Gear and full Oxygen Tanks - if you're wearing those then it's Advanced Rocketry which is stopping you breathing, not us. We are hoping the Advanced Rocketry guys will provide a config or other solution to avoid this conflict (like they did in the 1.7.10 version of their mod)
WAILA: some versions of WAILA have a bug where the color of grass, leaves, sand and some other blocks changes to grey when the player is mounted in a vehicle, including a Galacticraft rocket. If using WAWLA with WAILA, please make sure to use the latest Galacticraft version.
Cubic Chunks mod causes multiple weird issues with Galacticraft if you build outside the 0-255 height range - for example it can interfere with rocket launch and landing.
ViveCraft is compatible with Galacticraft, but it needs you to set a config setting: "Disable Vehicle Third-Person and Zoom"=true
Minor issues reported with PlayerRevive and Valkyrie Warfare mods.
Galacticraft 3: Compatibility with other mods
All information below is for Galacticraft 3, all recent versions - that's to say 1.7-184.108.40.2060 and above.
This topic will cover any known incompatibilities and what you can do about them. This topic is constantly updated when new issues come to light.
First off, you really should update to the latest Galacticraft version - it will have the latest compatibility fixes. The latest is the version at the top of the list on the Downloads page. The latest version includes the latest compatibility fixes - so it should normally be the most stable version.
For Galacticraft 2 compatibility information, see forum thread
Minecraft and Forge versions
See Installation Guide for details of the Minecraft, Forge and Java version requirements.
General compatibility notes
We intend for Galacticraft to be compatible with all popular mods. If you are having mod compatibility issues, please (1) update to latest Galacticraft (2) read this page to look for any specific issues and how to fix them. For severe issues - crashes or other obvious incompatibility - please report them to us on the Github issues list, if not already covered on this page.
If using Galacticraft with other mods or in modpacks, it is also strongly recommended to read Config#World_Generation.
Certain powerful blocks not working in another mod - solution: use Player API
A few mods detect and block actions by 'fake players'. 'Fake players' are robots, golems, and other things or machines which can mine or harvest like the player - anything which can simulate a right-click on blocks. For some mods, some things - usually the most powerful features, for example portals and altars - are only usable by real players, not by fake players, so the mod tries to detect and block fake players. Fake player detection can get confused by Galacticraft because the regular player is replaced by a Galacticraft player with extra inventory slots, oxygen levels, etc - if that happens, the other mod might block action by real players as well, when Galacticraft is installed.
If you are having problems of this kind with any other mod - basically something the player normally can do in the mod works fine if Galacticraft is not installed, but stops working and just seems to do nothing with Galacticraft installed - then first check you are using latest versions of both mods. Some mods - examples: Extra Utilities, Blood Magic - have added extra code for full Galacticraft compatibility, which we appreciate. (But even in the latest version of Extra Utilities, the portals to the Deep Dark and the Last Millennium do not work with Galacticraft unless Player API is installed: see next paragraph.)
If updating to latest versions did not solve the problem, then often issues of this kind will fix themselves if you have the Player API mod installed. To install Player API just place PlayerAPI-1.7.10-1.4.jar in your /mods folder. You don't need to do anything else: Player API simply works in the background, helping inter-mod compatibility.
Note: if playing on a server, PlayerAPI will need to be installed on both client and server.
Any other mods with energy and pipe connections
As of version 220.127.116.11 and all later versions, Galacticraft 3 has full power compatibility with:
- IndustrialCraft 2 (and GregTech)
- Thermal Expansion
- any other mod using RF power
That should give compatibility with most / all mods. For GregTech, you might need to update to recent (end 2017 / early 2018) versions. Any power compatibility issues, please let the developers know via the Github issues list. Note that Galacticraft configs allow players and server owners to switch off compatibility with some other power mods, if it is unwanted. So check your configs before reporting issues.
For information on power conversion ratios between mods, and how you can control whether conversion has losses or is loss-free, see Energy.
Fluid pipes from all mods should work with Galacticraft liquids. Galacticraft machines which handle liquids will accept fluid pipe connections from other mods - but note that (in Galacticraft 3) Galacticraft's oxygen and hydrogen systems will not accept gas pipes from other mods except Mekanism - in Galacticraft 4 the machines work with all pipes. Galacticraft machines which use liquids (for example Fuel Loader) will accept Galacticraft's own canisters, also buckets of the right type of liquid from other mods - perhaps also other types of fluid container, try it and see.
If you have wire or fluid pipe connection issues with any of these mods (and it's not already listed in the Known Issues, link above) please do let us know.
Code in other mods which looks for 'air' blocks
A few mods are coded to look only for vanilla air blocks when they are looking for space for something (for example, looking if there is enough room to build a multiblock structure). That is outdated coding. It will cause those mods to fail in some places with Galacticraft - for example in a sealed space base.
The Bukkit teleportation plugin, Essentials, has the same problem - it won't let you teleport into a sealed space. We recommend players who want to use Essentials teleport commands to access their base use an Air Lock, or you can maybe ask the Essentials team to fix this by using a Block.isAir() test.
If you have the Factorization mod installed, it has a nice feature called [AirInspector] which checks the code of all mods and tells you - in the logs - if a mod has this air block problem. It's then a question of showing those logs to the other mod authors and asking them to fix it. The other mods should update their code to use Block.isAir() or World.isAirBlock() for the air checks.
Sealing blocks from other mods
For sealers to work correctly, you might have to set the glass blocks from other mods - and any other special blocks which must be sealed on all 6 sides - in Galacticraft core config. Read Sealable Block IDs for full instructions.
Glass is a special block because you cannot place a torch on it. So think about anything else which you can't place a torch on...
You do not need to set regular solid blocks as sealable (e.g. ore blocks or machine blocks), Galacticraft already knows those are sealable. Galacticraft also understands about blocks which are solid on one side only, for example Facades in Forge Microblocks.
You cannot set leaves, or any block made out of cloth, gravel or sponge materials, as sealable - air goes through these blocks. This includes vanilla wool blocks and mod blocks made out of wool or cotton etc.
Note: if playing on a server, Sealable IDs is a server-only setting.
Ores from other mods not generating on planets
This is normal, Galacticraft 3 blocks other mods from generating ores on the Moon and other planets.
There is a config override which can enable the oregen from other mods, but it has problems:
- other mods will then generate all their ores, treating Moon Rock and Mars Stone as if they were plain stone which can make things look untidy underground
- other mods will also try to generate their other features and structures on the Moon, for example Natura clouds and flowers, IC2 rubber trees, Tinker's Construct slime islands, and many others; these are usually unwanted
- there can be 'Already Decorating!' crashes which are caused by rare bugs in the other mods' code (maybe they weren't expecting to be generating on the Moon?)
So we generally advise you not to enable that config setting. Instead, Galacticraft 3 offers a feature where Galacticraft will add other mods ores at the same time when it is generating Galacticraft's own ores on the Moon and Mars. You have to specify in Galacticraft's config the block IDs of the ores to generate, and how rare it is etc. Full instructions on this are here.
(Alternatively, since version 18.104.22.168 you can use CoFHCore custom oregen for similar control over this process, though that's a little more complex: link here.)
Note: if playing on a server, this is a server-only setting.
Mods which use Global IDs for their entities
Galacticraft does not use Global Entity IDs (and has not done since December 2014).
Some mods do still use Global IDs, which causes entity ID conflicts if the ID numbers clash. VoidMonster is one. OreSpawn was another (that's a huge mod with sub-mods (eg. Girlfriends) which add many new mobs to the game.)
If using any of these other mods, please update your Galacticraft to version 22.214.171.1246 or later, that will fix any possible incompatibility between Galacticraft and those other mods' entities (though the other mods may still clash with each other).
(Earlier Galacticraft versions may also be OK, though from versions 377 to 423 there could be entity registration problems in the other mods if the other mod chose entity IDs in the range 120-129 and loaded after Galacticraft. And if for some reason you are still using a version of Galacticraft prior to 245 you can change entity ID settings in Galacticraft's
mars.conf to try to solve conflicts. Normally it's only the creature mob entity IDs which will need to be changed - so Evolved Zombies, Evolved Creepers, Evolved Spiders, Evolved Skeletons, the two bosses, Alien Villagers, and Slimeling and Sludgeling. Change them to higher numbers (between 175 and 255) until you find ones which work. Entity ID settings in config files have no function in versions of Galacticraft 3 higher than 245, and can safely be edited out.)
Notes on some specific mods in Minecraft 1.7.10 (including fixable issues)
As of Galacticraft 3 version 426, there is full compatibility with Optifine Standard and Ultra - for example Optifine_1.7.10_HD_U_C1
Earlier Galacticraft versions had an issue where Optifine made the oxygen helmet and tanks invisible. (Optifine Lite did not have this problem.) It was previously recommended to install SmartRender from SmartMoving mod with PlayerAPI and RenderPlayerAPI, to overcome this Optifine problem. Installing those extra .jars is not necessary to use Optifine with Galacticraft version 426 or later.
(Fixable issue) Do not use the outdated version Optifine_1.7.10_HD_U_A4. It could make some of Galacticraft's blocks invisible, it had the same problem with other mods like Applied Energistics and Tinker's Construct. This was fixable by updating Optifine to version Optifine_1.7.10_HD_U_B5 or later.
Galacticraft generally pairs very well with Mekanism. Note that Mekanism was (as of March 2015) updated from v.7 to v.8. In Minecraft 1.7.10 versions:
- Galacticraft 126.96.36.1996 (and later) has dual support for Mekanism v.8 and Mekanism v.7.
- Galacticraft 3.0.9 (and earlier versions) had support for Mekanism v.7 only. Mekanism v.8 should not be used with these older Galacticraft versions - Mekanism v.8 gas systems (for example, Pressurised Tubes) will crash if used with Galacticraft 3.0.9 or earlier.
Full compatibility. Remember to set Clear Glass as a Sealable Block ID in Galacticraft core config, if you want to build space bases out of Clear Glass.
We have made it so Tinker's Construct stone torches work like regular torches in space - they will extinguish if there is no air, and re-light if oxygen is provided.
Galacticraft's metals from extraterrestrial sources (Meteoric Iron, Desh, and Titanium) cannot be smelted in a Tinker's Construct furnace nor made into any Tinker's Construct tools, and we have no current plans to add this feature - the space metals are not similar to any of the existing types of metal.
Full compatibility. IC2 batteries (of suitable tiers) can be charged in Galacticraft Energy Storage Module and Energy Storage Cluster and can power Galacticraft machines, and the other way around. Galacticraft power systems (Aluminium Wires, Energy Beams or Energy Storage Modules) can be used to power all IC2 machines, except for the Electric Kinetic Generator and the Electric Heat Generator.
There was an energy dupe (free energy creation) between IC2 and Galacticraft prior to Galacticraft version 410. Please update to version 411 or later if you are affected by this - servers should update.
Sealed versions of some IC2 cables can be made in Galacticraft - look up which ones in NEI.
Full compatibility. For detailed Buildcraft compatibility notes see Buildcraft.
Sealed versions of some Buildcraft pipes can be made in Galacticraft - look up which ones in NEI. These are stable as of Galacticraft version 426, and also work with BuildcraftCompat.
Galacticraft 3 is fully compatible with Smart Moving (requires Smart Render and Player API) as of GC3 version 188.8.131.526 (tested with SmartMoving-1.7.10-15.6, SmartRender-1.7.10-2.1 and PlayerAPI-1.7.10-1.4.) Galacticraft has been mostly compatible with Smart Moving since GC 184.108.40.206 but some issues remained, recently fixed in version 426.
For full compatibility with Galacticraft - to see the player oxygen tanks etc - you must install Render Player API with Smart Moving. (Tested with RenderPlayerAPI-1.7.10-1.4.)
Like other mods that change or affect the player model and its animations, Animated Player can break some Galacticraft animations (e.g. holding rocket, parachute descending etc). The problem can be fixed by installing Render Player API and Player API.
(Tested Animated Player 1.5.0 and Animation API 1.2.2: these are compatible with Galacticraft if you have Player API 1.4 and Render Player API 1.2 or later installed.)
RenderDecorator and VoxelPlayer
Galacticraft is compatible with RenderPlayerAPIEnhancer since GC version 426. Earlier GC versions could cause rare client-side crashes if a mob (for example Zombie Pigman, Zombie or Skeleton) spawned wearing special types of modded armor from another mod (for example Glowstone Armor from Mekanism).
If EnviroMine's "food rot" feature is enabled, please be sure to be using Galacticraft version 220.127.116.11 or later. (With earlier GC versions combined with EnviroMine, there were crashes when rockets were placed on launch pads - it didn't look anything connected with EnviroMine, but it was.)
Galacticraft is fully compatible with Sync mod, since GC version 426. Prior Galacticraft versions could lose part of Galacticraft's functionality when changing planets after a player was cloned.
Torches can be used to heat Ex Nihilo crucibles even in space environments, if there is oxygen so that the torch is burning. (This is as of Galacticraft version 411 and later.)
The recipe clash between GC canisters and Mariculture vats can be fixed by a setting in Galacticraft core config which allows an alternative recipe for canisters.
Mariculture disables other mods' smelting recipes for aluminum ore, so you won't be able to smelt Galacticraft Aluminum Ore at all, if Mariculture is installed.
If combining Mariculture with GregTech5, it's advisable to set Mariculture config:
Biome Top Block Replacements > Enable = false
(otherwise it can cause issues when Galacticraft is generating other planets). More details on this from Mariculture developer joshiejack.
In 2016 some GregTech builds the power systems were not compatible with IC2 or any other mod, including Galacticraft. We understand from GregTech developer that there is compatibility in 2017 versions, please try updating to latest.
Galacticraft's feature allowing other mods oregen on planets will not work to generate GregTech ores on Galacticraft planets. It's because GregTech uses a non-standard, extra-complicated way of identifying ore blocks in the world. Fortunately there is a third-party plugin for GregTech, GalactiGreg by BloodAsp, which can fix that for you. People also give some tips there on Galacticraft sealer config settings when playing with GregTech.
If you find that the ExtraUtilities portals for the Deep Dark and the Last Millennium are not working, that can be fixed by installing PlayerAPI alongside Galacticraft.
ExtraUtilities also needs PlayerAPI for the Etheric Sword + Soul Fragment health restoration (when a Soul Fragment is right-clicked) to work properly.
Use Galacticraft 3 version 426 or later with Multiverse. In prior versions, to ensure the Galacticraft dimensions are loaded at server start so that Multiverse knows how to send players to the dimensions, you had to go into the Galacticraft/core.conf file and add the dimensions -28, -29, -30, one on each line, inside the "I:"Static Loaded Dimensions"" braces. Further reading
The above may also help to fix errors of this type:
Could not pass event PlayerTeleportEvent to Multiverse-Core
There is a biome ID overlap between Erebus and Galacticraft, both mods are trying to use biome IDs 102-105. This can cause weird issues with GC biomes sometimes generating in the Overworld, or occasionally crashes in Erebus (see here). To fix this, in Erebus config, change the biome IDs 102, 103, 104, 105. You can probably use 106, 107, 108, 110.
Alternatively, in recent Galacticraft versions you can change the Galacticraft biome base ID in configs. You would need to regenerate all your Galacticraft dimensions after changing this for it to take full effect (otherwise the space dimensions will be labelled as being Erebus biomes still).
(Small issue) There is a position clash with Custom NPCs 'Quests' buttons in the player inventory, but you can reach the Quests dialog by clicking on 'Factions' first, then 'Quests'. Link These issues are fixed in more recent versions of Custom NPCs. (With Galacticraft 4 make sure your Custom NPCs version is from May 2017 or later.)
Make sure to use Galacticraft version 426 or higher with Dynamic Lights. (There was a problem in GC versions 411 through to 425.)
Fancy Cloud Handling will break Galacticraft in all space dimensions - the look of the dimension will be off, maybe also the gravity will be wrong. You can disable Fancy Cloud Handling in the config of Dynamic Surroundings (dsurround.cfg).
Dynamic Surroundings, since version 1.10.2-18.104.22.168, supports Galacticraft dimensions. For Galacticraft 1.7.10 and 1.8.9, use the cfg files available here.
These will need to be fixed by the authors of the other mods.
More Player Models
We cannot offer compatibility with this mod, as it uses an approach which is not really compatible with other mods. You may have improved results if you install Player API and Render Player API, try it and see.
More Player Models has been reported to be crashing with Galacticraft here
Too Much Time
This mod's dimension handling will cause crashes whenever you travel to a Galacticraft dimension, so basically Galacticraft is unplayable if you have Too Much Time installed.
Karyonix GLSL Shaders Mod is currently unsupported; the sky will not look good on Galacticraft planets or space environments. Best would be if that mod can auto-disable itself in Galacticraft dimensions.
(Small issue) The Rocket Propelled Torch (RPT) Launcher will not work correctly in Galacticraft's airless dimensions. The RPT Launcher will place lit torches, not unlit torches - and these lit torches will stay lit even without air. The RPT Launcher cannot be re-filled with torches while the player stays in an airless dimension.
(Small issue) A rare issue with the Twilight Forest Scepter item has been reported, causing blocks to be drawn darker than normal in Space Station dimensions. Link
DragonAPI (recent versions)
(Small issue) If this mod is present and Galacticraft is also installed, a player in Minecraft's third person view will be drawn solid like normal, even if the player is underwater (or in some other kind of liquid). Screenshots
Issues and bugs in other mods (and how to fix them!)
All of the issues described in the following section are caused by other mods. The latest versions of Galacticraft include workarounds to make it less likely that these type of problems will arise. With older versions of Galacticraft there may also be steps you can take to fix these issues yourself, see below.
The world xxxxxxxx (world) may have leaked: seen 25 times
This type of information message is sometimes seen in server logs. If the named world xxxxxxxx is a Galacticraft dimension - for example, the Moon - this does not mean there is an issue in Galacticraft. The log message is telling you where the issue is - which dimension it is in -- but not which mod caused the issue. Don't blame Galacticraft! Galacticraft provides the dimensions, but doesn't cause the issue. Obviously, if you have 50 mods installed and you place blocks from all of those mods in your Moon base, then it could be any of those mods causing the issue.
A 'world leak' is not a serious problem at all. It is a small memory leak, meaning that if you run a server for several hours, your Java base memory use, the minimum memory used by the game, will very slowly increase over that time - it will increase a little bit any time a player goes to the world which is 'leaking' and then leaves it again. The reason for a world leak is bad programming style by a mod author, very hard to track down, and most programmers do it every once in a while.
Players who are not mod developers or the admins of large public servers really do not need to worry about this.
'Already decorating!' crashes on the Moon (or other Galacticraft worlds)
These do not occur in Galacticraft 3 itself since around version 300 or later. If you see this, the cause is almost certainly another mod. Look through the crash report's stacktrace carefully and try to see which mods' code is mentioned lower down in the trace.
In outdated versions of Galacticraft prior to 297, the CofHCore 'Flat Bedrock' feature (which can be enabled in CofH configs) could cause this 'Already decorating!' crash, usually fixable by going into the CoFHWorld.cfg file and setting the number of layers of bedrock to 1. (In recent versions of CoFHCore the config file is
CoFH/Core/Common.cfg.) Note: if playing on a server, this is a server-only fix.
(For info: CoFH replaces all blocks down there with bedrock before the chunk is fully generated. This causes problems if CoFHCore over-writes a block which has a TileEntity. That's a bug in CoFHCore - mods should not change blocks with TileEntities before the chunk and its neighbours are fully generated, because over-writing a block with a TileEntity causes a block update on the neighbours which can mean the neighbouring chunk in turn has to be generated, potentially producing an infinite worldgen loop. Galacticraft has included a special patch which works around this issue by delaying TileEntity creation if CoFHCore is active.)
Crash report with GCEntityClientPlayerMP
People sometimes think that a crash report containing a line like this: 'micdoodle8.mods.galacticraft.core.entities.player.GCEntityClientPlayerMP' somewhere in the middle is a Galacticraft bug. It isn't! OK, in 99% of cases it isn't. The crash is just passing through Galacticraft, the same way that it passes through all those bits of vanilla Minecraft code that you also see in crash reports. Further reading.
These types of crash reports can also be seen with GCEntityPlayerMP, GCPlayerBaseSP, and occasionally other GC entities. Quite often the crashes seem to be connected with other mods which did not register new potion effects (e.g. dizziness, radiation poisoning) correctly. Stuff like that. Not space stuff.
If you're reading this section of this page, it's probably because you are still using DragonAPI 1.7.10 version 2 which is not the latest version. The issue here has been fixed in DragonAPI 1.7.10 version 3 and later, and players should update to that.
More info: in recent Galacticraft versions DragonAPI v2 will be detected during startup and you will be referred to this page. In earlier Galacticraft versions (prior to 22.214.171.124), the game would crash when you take a rocket, with this in the crash report:
The issue was because of DragonAPI v2 force-loading a piece of outdated Galacticraft code in advance of Galacticraft itself. As mentioned above, this has long since been fixed in DragonAPI v3, so if you're using v3 you should be fine. But if for some reason you have to use DragonAPI v2 (because of a modpack which has not updated), then you can fix the issue yourself by a manual edit of the DragonAPI.jar.
- Find the DragonAPI 1.7.10 V2.jar file in your
- Open the .jar using any program which can create a Zip file (for example, 7Zip is free and open source)
- Delete the folder
Note: if playing on a server, it will need to be fixed on both client and server.
For clients running OpenJDK
Several Linux distributions include OpenJDK for running Java, instead of the Java Runtime (JRE) from Sun / Oracle.
OpenJDK has a bug in its JPEG library. Galacticraft makes a very minor use of the standard JPEG library to save some map images to disk on the client - folder assets/GalacticraftMaps - so that you can look at them outside the game (similar to the images seen in a Display Screen).
At one time (prior to Galacticraft version 126.96.36.1997) this OpenJDK bug could cause [startup issues on Linux servers]) but Galacticraft now works around this, disabling the JPEG library use if there are problems with it, and showing a message in logs linking to here.
In Galacticraft 4 and recent versions of Galacticraft 3, servers do not make use of the JPEG library at all. Player clients only use it for saving images to disk as explained above, it does not affect gameplay if it is not present.