Users and sudo

Many users, one computer

• Linux was built for many people to share one machine safely.
• Each person has a user account. whoami tells you who you currently are:

whoami

• File ownership does not make files private. Their permissions determine which ordinary users can read or change them; administrators may have additional access.

The superuser: root

• One special user, root, has extensive administrator privileges, such as installing software and managing users. System security controls can still impose limits.
• With great power comes great danger: a wrong command as root can break the whole system.
• So you normally work as an ordinary user, and only become root when you must.

sudo — borrow root for one command

• When policy permits, sudo runs a command as another user, normally root. It may ask for your password; cached authentication or policy can remove that prompt:

sudo apt install git

• Use it only when a task needs the permitted administrator rights. Read the command twice before pressing Enter. Our simulator supports whoami and hostname, but does not grant real administrator access.

Common mistakes

• sudo runs one command as the administrator — use it carefully.
• Do not put sudo in front of everything.