User management in Raspbian is done on the command line. The default user is pi, and the password is raspberry. You can add users and change each user's password.
Once you're logged in as the pi user, it is highly advisable to use the passwd command to change the default password to improve your Pi's security.
Enter passwd on the command line and press Enter. You'll be prompted to enter your current password to authenticate, and then asked for a new password. Press Enter on completion and you'll be asked to confirm it. Note that no characters will be displayed while entering your password. Once you've correctly confirmed your password, you'll be shown a success message (passwd: password updated successfully), and the new password will apply immediately.
If your user has sudo permissions, you can change another user's password with passwd followed by the user's username. For example, sudo passwd bob will allow you to set the user bob's password, and then some additional optional values for the user such as their name. Just press Enter to skip each of these options.
You can remove the password for the user bob with sudo passwd bob -d.
You can create additional users on your Raspbian installation with the adduser command.
Enter sudo adduser bob and you'll be prompted for a password for the new user bob. Leave this blank if you don't want a password.
When you create a new user, they will have a home folder in /home/. The pi user's home folder is at /home/pi/.
Upon creating a new user, the contents of /etc/skel/ will be copied to the new user's home folder. You can add or modify dot-files such as the .bashrc in /etc/skel/ to your requirements, and this version will be applied to new users.
The default pi user on Raspbian is a member of the sudo group. This gives the ability to run commands as root when preceded by sudo, and to switch to the root user with sudo su.
To add a new user to the sudo group, use the adduser command:
sudo adduser bob sudoNote that the user bob will be prompted to enter their password when they run sudo. This differs from the behaviour of the pi user, since pi is not prompted for their password. If you wish to remove the password prompt from the new user, create a custom sudoers file and place it in the /etc/sudoers.d directory:
echo 'bob ALL=(ALL) NOPASSWD: ALL' | sudo tee /etc/sudoers.d/010_bob-nopasswdNote that it is standard practice on Linux to have the user prompted for their password when they run sudo, since it makes the system slightly more secure.
You can delete a user on your system with the command userdel. Apply the -r flag to remove their home folder too:
sudo userdel -r bob