[zygology]

You can't make them on the filesystem itself, gen_init_cpio lets you specify device nodes to be created within the archive, but they are not actually created on the live system and do not require privileges.

I made my own CPIO library: https://github.com/desultory/pycpio and one of the main goals was this behavior, so I could create CPIO archives with device nodes without privileges. It's really as simple as writing some bytes to a file saying "when you extract this, create this device node". It's not like any archive actually has a device node, just instructions for where to put them, and what properties they have.

Certainly, you can't extract these archives as non-root, but you have to go out of your way to make an initramfs have non-root privileges.