Cybersecurity

Generally, root and admin ids use root as home, not application users. User and app files should not clutter root, they should be in dedicated sub-directories. Some users like to try to run flat with almost no directories, but that is not good practice. Usually, each user gets a /home/<user_name>/ home dir.

Groups can be created with groupadd, and users can be attached at creation time or later, but if the critical group is not the original, default group, the user may need to newgrp to change groups. If you have a user and files/dirs you want to share, their group you want on this id is on these files/dirs. If they are still inaccessible with matching groups, and you want this, "chmod -R g+rw <top_dir>" will ensure all have group read write on the whole sub-tree.

When I login to the terminal and run the command whoami i get ubuntu
pwd command returns /home/ubuntu

Am I the administrator. [I am doing this on my computer for learning. ]?
I need to create another user. Do i change my settings and become the admin?

Even when you login as johns ? The home dir is defined in /etc/passwd unless they moved it. Perhaps use sudo to make johns a home dir, set the ownership, group and modes, and then change the johns login home dir. I expect root is the admin superuser, still, and ubuntu is the default first user. You don't want to run around crushing things accidentally as superuser. sudo takes you to root

in /etc/passwd there is a line
johns:x:1000:1000::/home/johns:bin/sh

But when i try to go cd /home/johns I get 'No such file or directory'

Perhaps use sudo to make johns a home dir, set the ownership, group and modes, and then change the johns login home dir. ? How do i do this?

Code:

sudo mkdir /home/johns
sudo chown johns /home/johns
sudo chgrp <diff_group> /home/johns # if_diff_group
sudo chmod 755 /home/johns

Usually, the final, login shell field starts with a / (absolute path): johns:x:1000:1000::/home/johns:/bin/sh

I created the folder johns and made john the owner of it.
But when i try to login, I get the message 'johns is not in the sudoers file. This incident will be reported'

Also when i try to change the group , it says says <diff_group> is not valid

If you have a different group, you need to run that line with the different group. <diff_group> is a meta-string for your replacement.

Maybe you need to hit the man pages to add johns to the sudoers file, if you want thate login to have that much power, or go back to bare login, or even bare su.