ps -H -A
can show the relationship between all the processes in a tree format. it is helpful when you want to research the internals of UNIX.
init
keventd
ksoftirqd/0
bdflush
kswapd
we can see from the above that all the process are the children of init (directly or indirectly). especially the kernel thread are also the children of init process.
process 0 is special, it is not displayed.
From the following:
sshd
sshd
sshd
bash
vim
cscope
sshd
sshd
bash
ps
we can see that how ssh works. actually I have created two ssh session to the server.