Run part of a bash script as a different user

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?

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

# 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