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I am in Ubuntu 9.04. Is there a way to make part of a script run as a different (non-root) user? If it helps, the part to be run as a different user occurs at the end of the script.

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7 Answers 7

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60

Use the sudo command in the script.

In the form:

sudo -u username command

the sudo command runs command as the user username.

If the script is being run as root, I don't think it will prompt for a password. Otherwise, this article discusses how to use sudo with password in one command line?, and this article discusses how to use sudo without password?

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  • 9
    This is nice and easy, but is there a way to do this for a group of commands instead of one at a time?
    – Andrew
    Dec 5, 2013 at 23:08
  • 2
    write a bash script, make it executable chmod +x script.sh and then just sudo -u username script.sh
    – 55651909-089b-4e04-9408-47c5bf
    Jun 11, 2014 at 15:05
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    @Andrew I was wondering this myself and the following worked for me: sudo -u ic sh -c 'cmd1 && cmd2'
    – Karussell
    May 29, 2017 at 14:26
  • Also include the i option if you want to acquire the user's environment
    – neoDev
    Nov 21, 2017 at 6:17
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# I=like:

#test if running bash as a different user works
sudo -u nobody bash -c : && RUNAS="sudo -u nobody"

echo 1: $USER

#Runs bash with commands between '_' as nobody if possible
$RUNAS bash<<_
echo 2: \$USER
_

echo 3: $USER

# ./run

1: root
2: nobody
3: root
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8

This answer is good, but the serverfault advice is slightly dangerous - would allow anyone to run anything as root! So I'm posting here because I can't format the comment.

I would recommend using visudo to give the permissions you need as precisely as you can. Type visudo and add a line like:

username hostname = NOPASSWD: /full/path/to/command1, full/path/to/command2

If you do need to run this same thing on many hosts, you could open it up with:

username ALL = NOPASSWD: /full/path/to/command1, full/path/to/command2

But I would **not* use either:

username ALL=(ALL) NOPASSWD: ALL

or username hostname = ALL

The sudoer man page has lots of gory details

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  • Would it work for a command available to a particular user only ?
    – Manish Mathai
    Jan 9, 2010 at 9:42
  • You can specify that only particular users can run the command (in the examples above, replace username with the username who should be able to run the command). If the executable you want to run is only executable by one particular user, that's fine too - just pass that username in the sudo -u username commandline line of the script.
    – James Polley
    Jan 9, 2010 at 10:31
  • @Manish. Yes. What the sudoers file says is "Allow this username on this host to run command1 without having to provide a password.
    – DaveParillo
    Jan 9, 2010 at 17:23
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This way, end of a script will be executed by different user (root). Please note the $[LINENO+2] and exit $? calls. These are required to make the end of the script to execute just once and to preserve the exit code of the sudo call.

#!/bin/bash                                                                                                                                                                                                                                  
echo $USER                                                                                                                                                                                                                                      

# pipe the rest of this script via a sudo call                                                                                                                                                                                                                                         
tail -n +$[LINENO+2] $0 | exec sudo bash                                                                                                                                                                                                     
exit $?                                                                                                                                                                                                                                     
echo $USER
exit 1
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For sonarqube:

sudo -u sonar /usr/bin/sonar start

where sonar is the name of user used to run the command /usr/bin/sonar start

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not so sure about it, but if you want that ONLY the end of that script will run as a different user, you could add su someuser before the end of the script.

Am I missing something?

Hope that helps,

Regards

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    I think this is the most appropriate answer, having all other answers suggesting sudo, which is often not installed by default on some minimal linux installations.
    – Tim
    Jan 7, 2018 at 3:04
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    su someuser will start a new shell, it won't execute the rest of the script.
    – Just a student
    Feb 14, 2020 at 15:43
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    Yeah this won't work, it'll just go into a new shell then do nothing forever, the rest of the script won't be executed
    – Shardj
    Jan 25, 2022 at 12:43
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I had a similar need as the OP, I had a good sized shell script that needs to be run as root, but a good portion of which I need to have run as another user. My solution was to put the entire contents of script (both the part that needs to be run by root, and the part that needs to be run as "other_user") in an if/elif block:

if [ $USER = "other_user" ]
then
   ## Run commands as user other_user
   :
   exit
elif [ $USER = "root" ]
then
   ## Run some commands as root
   :
   ## Next, run this script as other_user
   sudo -i -u other_user $0 "$@"
   ## Then run more commands as root
   :
else
   ## Nobody else should run this script
   echo "Permission denied"
   exit 1
fi
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