How to make a script run commands as root

Question

I'm new to Ubuntu and bash scripts, but I just made runUpdates.sh and added this to my .profile to run it:

if [ -f "$HOME/bin/runUpdates.sh" ]; then
    . "$HOME/bin/runUpdates.sh"
fi

The problem I'm having is, I want the script to run as if root is running it (because I don't want to type my sudo password)

I found a few places that I should be able to do sudo chown root.root <my script> and sudo chmod 4755 <my script> and when I run it, it should run as root. But it's not...

The script looks good to me. What am I missing? -rwxr-xr-x 1 root root 851 Mar 23 21:14 runUpdates.sh*

Can you please help me run the commands in this script as root? I don't really want to change the sudors file, I really just want to run the commands in this script at root (if possible).

#!/bin/sh

echo "user is ${USER}"

#check for updates
update=`cat /var/lib/update-notifier/updates-available | head -c 2 | tail -c 1`;
if [ "$update" = "0" ]; then
        echo -e "No updates found.\n";
else
        read -p "Do you wish to install updates? [yN] " yn
        if [ "$yn" != "y" ] && [ "$yn" != "Y" ]; then
                echo -e 'No\n';
        else
                echo "Please wait...";
                echo `sudo apt-get update`;
                echo `sudo apt-get upgrade`;
                echo `sudo apt-get dist-upgrade`;
                echo -e "Done!\n";
        fi
fi

#check for restart
restartFile=`/usr/lib/update-notifier/update-motd-reboot-required`;
if [ ! -z "$restartFile" ]; then
        echo "$restartFile";
        read -p "Do you wish to REBOOT? [yN] " yn
        if [ "$yn" != "y" ] && [ "$yn" != "Y" ]; then
                echo -e 'No\n';
        else
                echo `sudo shutdown -r now`;
        fi
fi

I added the user is to debug, it always outputs my user not root, and prompts for the sudo password (since I'm calling the commands with sudo) or tells me are you root? (if I remove sudo)

Also, is there a way to output the update commands stdout in real time, not just one block when they finish?

(I also tried with the shebang as #!/bin/bash)

user4098326 · Accepted Answer · 2015-03-24 03:02:07Z

7

setuid does not work on shell scripts for security reasons. If you want to run a script as root without a password, you can edit /etc/sudoers to allow it to be run with sudo without a password.

To "update in real time", you would run the command directly instead of using echo.

answered Mar 24, 2015 at 3:02

user4098326

1,7624 gold badges16 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

KPK Over a year ago

Thank you! I'm new to all this, but I don't understand how this could be safer. If the script could be set to run as root, only that could run as root (right?) But with /etc/sudors I have to give the path to the file. What if someone rm's the existing file and puts there own there. Wont that unintended script be able to run as a super user now?

miken32 Over a year ago

That's why you change the ownership and permissions of the file to prevent tampering by unprivileged users.

user4098326 Over a year ago

@KPK In addition to file system permissions, if sudo is 1.8.7 or later, you can also use Digest_Spec in sudoers, so it only matches when the SHA-2 digest is correct.

score 5 · Accepted Answer · 2015-03-24 20:16:54Z

Its not safe to do, you should probably use sudoers but if you really need/want to, you can do it with something like this:

echo <root password> | sudo -S echo -n 2>/dev/random 1>/dev/random
sudo <command>

This works because sudo doesn't require a password for a brief window after successfully being used.

SUID root scripts were phased out many years ago if you really want to run scripts as root you need to wrap them in an executable, you can see an example on how to do this on my blog: http://scriptsandoneliners.blogspot.com/2015/01/sanitizing-dangerous-yet-useful-commands.html

The example is how to change executable permissions and place a filter around other executables using a shell script but the concept of wrapping a shell script works for SUID as well, the resulting executable file from the shell script can be made SUID.

https://help.ubuntu.com/community/Sudoers

Collectives™ on Stack Overflow

How to make a script run commands as root

2 Answers 2

3 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related