sudo

Additional Notes

sudo runs a command with another user's privileges, usually root. It is used for system administration tasks such as installing packages, editing system files, restarting services, and changing ownership.

sudo is safer than logging in as root for daily work because it gives temporary privilege only to the command that needs it.

Syntax

sudo [options] command

Parameters

• options: Flags that change how sudo behaves.
• user: User account affected by the command.
• group: Group account affected by the command.
• file: File or directory whose ownership, mode, or access policy is being changed.

Common Options

• -u USER: Run as a specific user.
• -i: Start a login shell as the target user.
• -s: Start a shell using the current environment.
• -l: List commands your user is allowed to run.
• -v: Validate or refresh cached credentials.
• -k: Invalidate cached credentials.
• -E: Preserve the environment when allowed.

Examples

sudo apt update

Run a package-management command as root.

sudo systemctl restart nginx

Restart a system service.

sudo -u postgres psql

Run psql as the postgres user.

sudo -l

Show what your user is allowed to run with sudo.

sudo -i

Open a root login shell.

Practical Notes

• Use sudo only when a command needs elevated privileges.
• Running normal commands as root can create files your user cannot edit later.
• sudo permissions are usually configured in /etc/sudoers or files under /etc/sudoers.d.
• Use visudo to edit sudoers safely.
• Be extra careful with commands that delete, overwrite, or recursively change files.