Linux – What process is the parent of the init process in Linux

Add the l option to your ps command line. This is the option for long output. The parent process id is one of the additional columns -- labeled PPID.

$ ps l
F   UID   PID  PPID PRI  NI    VSZ   RSS WCHAN  STAT TTY        TIME COMMAND
0   508  3344  4498  18   0   2452  1236 wait   Ss   pts/12     0:00 /bin/sh
0   508  4467 17796  15   0   4664  1572 wait   Ss   pts/5      0:00 -/bin/bash
0   508  4498  4467  15   0  23032 15108 -      S+   pts/5      2:20 emacs -nw
0   508  4532 17796  15   0   4532  1464 wait   Ss   pts/13     0:00 -/bin/bash
0   508  4916 17796  15   0   4664  1648 wait   Ss   pts/7      0:01 -/bin/bash

Another option is the pstree command to show an ascii tree representation of the processes. You'll probably want the -p option to show process ids.

$ pstree -p dharris
screen(17796)─┬─bash(4467)───emacs(4498)───sh(3344)───sh(3345)
              ├─bash(4532)───su(31037)───bash(31041)
              ├─bash(4916)───pstree(26456)
              ├─bash(13547)───su(20442)───bash(20443)
              └─bash(17797)

sshd(25813)───bash(25817)───screen(25870)

Short answers:

1. No, it's not a process
2. User threads are not rooted at init.

Init is just the first process; it does not manage any proceses or threads. It does create some, using the kernel syscalls fork() and exec.

I think you have a muddy idea of what a process is. it doesn't just mean a bit of executing code. Yeah, the kernel executes before init (and the boot loader before that even). But a 'process' has a specific definition of:

• Runs in user space
• Runs with a process ID
• Many interactions need to go through the kernel
• All resources need to come from kernel
• Needs to be scheduled by kernel

So, once the kernel initializes, it runs init, which then spawns whatever other processes its configuration says to.

As far as #2 goes, all the kernel stuff is, well, in the kernel. Think of the kernel as a large area of code. Again, not a process, but a large code blob. Parts of the kernel deal with memory management, parts of it with scheduling portions of itself (like drivers, etc.), and parts of it with scheduling processes.