How do I run nohup as a different user without spawning two processes?

Question

I'm trying to nohup a command and run it as a different user, but every time I do this two processes are spawned.

For example:

$ nohup su -s /bin/bash nobody -c "my_command" > outfile.txt &

This definitely runs my_command as nobody, but there's an extra process that I don't want to shown up:

$ ps -Af
.
.
.
root ... su -s /bin/bash nobody my_command
nobody ... my_command

And if I kill the root process, the nobody process still lives... but is there a way to not run the root process at all? Since getting the id of my_command and killing it is a bit more complicated.

Answer 1

This could be achieved as:

su nobody -c "nohup my_command >/dev/null 2>&1 &"

and to write the pid of 'my_command' in a pidFile:

pidFile=/var/run/myAppName.pid
touch $pidFile
chown nobody:nobody $pidFile
su nobody -c "nohup my_command >/dev/null 2>&1 & echo \$! > '$pidFile'"

Answer 2

nohup runuser nobody -c "my_command my_command_args....." < /dev/null >> /tmp/mylogfile 2>&1 &

Answer 3

If the user with nologin shell, run as follows:

su - nobody -s /bin/sh -c "nohup your_command parameter  >/dev/null 2>&1 &"

Or:

runuser - nobody -s /bin/sh -c "nohup your_command parameter  >/dev/null 2>&1 &"

Or:

sudo su - nobody -s /bin/sh -c "nohup your_command parameter  >/dev/null 2>&1 &"

sudo runuser -u nobody -s /bin/sh -c "nohup your_command parameter  >/dev/null 2>&1 &"

Answer 4

You might do best to create a small script in e.g. /usr/local/bin/start_my_command like this:

#!/bin/bash
nohup my_command > outfile.txt &

Use chown and chmod to set it to be executable and owned by nobody, then just run su nobody -c /usr/local/bin/start_my_command.