Add a sudoer non-interactively from command line

I had a similar issue trying to get my docker container to allow jenkins scripts to use sudo commands without prompting for a password.

This was solved via the Dockerfile:

RUN echo "jenkins ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers

To be able to do that, you should make sure you have the following line in your sudoers file:

%sudo   ALL=(ALL:ALL) ALL

You can customize the above line to change the permissions just as though %sudo was a user. That line will allow any users in the sudo group to use sudo.

Now to allow <username> to use sudo, you can just do usermod -a -G sudo <username> as root, which adds <username> to the sudo group.

You could use cat to append text to the end of /etc/sudoers. First, make a backup copy of your /etc/sudoers file. Then:

cat >> /etc/sudoers
...type one or more lines here...
[control-D]

Make absolutely sure to use two greater-than characters (>>) and not just one, or else you will overwrite the entire contents of your file.