Running a bash install script as root - how to handle regular users' files?

Question

I am writing some bash scripts to install and configure some programs.
Because the script needs to install packages - I run the scripts as root - which itself is no problem (ie I have root privileges etc).

However once the packages are installed the script needs to configure normal user files and fetch plugins etc, eg

• sed is/xxx/mod_to_make/ <user_config_file>
• git clone <plugin>
• wget <plugin>
• etc

Ideally I would do this as a regular user because I don't want these git repos and files to be owned by root,

An example program snippet is something like

#! /bin/bash

# Because this statement needs to be run as root - the entire script is 
# also run as root
apt-get install -y tmux

cat << EOF > ~/.tmux.conf
# 
# config stuff
#
EOF

Do I need to manually revert file privileges to regular user, at the end of the script, eg

chown $USER:$USER ~/.tmux.conf 
chmod 755 ~/.tmux.conf 

Or write 2 separate scripts 1 run by a root the other as regular user ?

Or is there a better way to handle this?

Answer 1

Just because we usually associate sudo as a means to become root, it doesnt mean it cannot be used by root to become a user.

So just prefix the commands you need to run as $USER by

sudo -u $USER ....

To make it easier to have all in one script, collect all the root code into a function and all the user code into another function, then run the script as root, and it can then run the same script as USER. We check the id of the person running the script and do one function or the other. eg:

#!/bin/bash
rootstuff(){
  ....
  [ "$USER" != root ] && sudo -u $USER $0
}
userstuff(){
  ....
}

if [[ $(id) = uid=0* ]]
then  echo root
      rootstuff
else  echo user
      userstuff
fi

Make sure USER is not root.

Answer 2

If you have a bunch of consecutive codes which should be run as regular user (not root), then you can do this:

sudo -s -u $USER<<EOF
echo "running codes as normal user"
EOF

Note: You may need to check if $USER is a regular user or root. If you run the script in a root shell, the value of $USER will be root and that's the normal and expected behavior, ie whatever user specific files you are creating are expected to be created in the root environment.