[Info-vax] Orphaned processes on OpenVMS

[Johnny Billquist]

On 2011-05-20 06.30, Bob Koehler wrote:
[...]
>     In UNIX, all processes except init have a parent.  There is no
>     concept of a detached process.  If you kill a process all subprocesses
>     are inherited by the next parent up the tree.  You can't kill init.
>     The closest thing to a job tree is that most shells will tell you
>     all the children below the shell process, but the shell process
>     itself has a parent.

A small nitpick: every Unix implementation I've ever seen moves orphaned 
children directly to init, and don't traverse them to parents. There 
could be some unexpected complications if you did something like that.

You can send signals to init, just like any other process (killing a 
process in Unix really is just a question of sending it a signal). 
However, if init ever dies, bad things happen. So it protects itself 
from most signals, and it might be protected by the OS from the 
non-catchable signals.

Also, formally, init also have a parent. Although that is the kernel 
itself. Init is always pid 1, while the kernel acts out as pid 0. And 
pid 0 is its own parent. And pid 0 is in most implementations not a 
process in exactly the full sense of the word.

All this is easily available to be examined by running ps. :-)
But it's not really VMS. So lets get back on topic.

	Johnny