I thought that the init system spawned everything. Is this a bug in
No it is not, kthreadd is not spawned by anything and is handled by the kernel.
Thank you, @redstrate. Do you know of where I can read more about this?
There’s not much public information online just searching for “kthreadd” because it’s the daemon that handles spawning threads for kernel use. There is some documentation on kthread.c « kernel - kernel/git/torvalds/linux.git - Linux kernel source tree I guess?