[Raspberry pi]

[NiLSPACE]

It's a little complicated but here is a quick tutorial

1.) You have to create a new world in the settings.ini

Code:

[Worlds]
DefaultWorld=world
World=world_nether

2.) Then create a folder named world_nether
3.) Create a world.ini and add

Code:

[Generator]
BiomeGen=Constant
ConstantBiome=Nether
HeightGen=Flat
CompositionGen=Nether
FlatHeight=128
Structures=Ravines,WormNestCaves
Finishers=LavaSprings,BottomLava,NetherClumpFoliage,PreSimulator
BottomLavaLevel=30
Generator=Composable
HeightGenCacheSize=64
NetherThreshold=0
CompositionGenCacheSize=64

[General]
Dimension=-1

4.) Let the world generate.

5.) Set proper spawn coordinates. The default will spawn you ontop of the bedrock, and you don't want that if you are in survival don't you think?
You can do this by going to the world, find a nice spot and then press f3 to see your current coordines. Then you can change the [SpawnPosition] in the world.ini

Then you can use the /portal command to swap worlds: /portal world_nether