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.
When logged in as the pi user, you can change your password with the passwd command.
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 preceded 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 sudoer. 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 sudoers, type sudo visudo (from a sudoer user) and find the line root ALL=(ALL:ALL) ALL, under the commented header # User privilege specification. Copy this line and switch from root to the username. To allow passwordless root access, change to NOPASSWD: ALL. The example below gives the user bob passwordless sudo access:
# User privilege specification
root ALL=(ALL:ALL) ALL
bob ALL = NOPASSWD: ALLSave and exit to apply the changes. Be careful, as it's possible to remove your own sudo rights by accident.
You can change the editor the visudo command uses (the default is Nano) by entering:
update-alternatives --set editor /usr/bin/vim.tinyThis sets the editor to Vim.
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