magic with nohup

r_s · 11-08-2012, 02:52 AM

I have two files file1 and file2. Within file2 I am running a daemon in the background as user user1.
And I am executing this file2 from within file1, running file1 as root. This creates two process one being executed as root and the other as user1. However if add a nohup before the invocation of the daemon in file2, it shows only one process being run as user1.

A little more explanation.

file1

Code:

#!/bin/bash
file2

file2

Code:

#!/bin/bash
sudo -u user1 java daemon &

and now ps aux gives..

Code:

root   file2
user1  java daemon &

however adding a nohup to file2, like

Code:

nohup sudo -u user1 java daemon &

shows just one process running as user1.

chrism01 · 11-08-2012, 04:13 AM

That's because nohup disconnects from the calling process; that's what its supposed to do. Hence, the calling script immediately runs to completion.
You can use a few echo statements to see the difference, or add 'set -xv' thus

Code:

#!/bin/bash
set -xv