The Console - Learning Raspbian - page 105

The addgroup command is simple to use. All you need to do is to add the name of
the group after the addgroup command.
The new group will be created along with a new ID. To see the groups that are there
in Raspbian, run the following command:
cat /etc/group
passwd
As the system administrator of your very own Linux system, you have a lot of
power. You can use this power to change users' passwords using the passwd
command. There are a couple of different ways in which you can use passwd .
One of them is to change your own password. Another way in which you can
use passwd is to change the password of another user on your system.
Changing your password
To change your own password, run the passwd command as shown in the
following screenshot:
Changing your password
This will ask you to enter your current password. After you enter this, you will need
to enter the new password twice.
Changing another user's password
Changing another user's password is just as easy as changing your password. To do
this, add the username of the user after the passwd command. This command needs
to be run as root, so add sudo before it.
Changing another user's password
This is really useful if you need to change someone else's password. By default, there
is no root password set in Raspbian. To set it, run sudo passwd .