Cheatsheet & Examples: sudo
The sudo command allows a permitted user to execute a command as the superuser (root) or another user, providing elevated (administrator) privileges.
Run a Command as Root
Example Usage:
sudo apt update
What it does:
Runs the apt update command with root privileges to refresh package lists.
Command-line Arguments Explained:
sudo: Executes the following command with elevated privileges.apt: Package management tool used on Debian-based systems.update: Refreshes the local package index.
Run a Command with a Specific User
Example Usage:
sudo -u www-data ls /var/www
What it does:
Runs the ls /var/www command as the user www-data.
Command-line Arguments Explained:
sudo: Grants elevated or user-specified privileges.-u: Specifies which user to run the command as.www-data: The user account to use (in this case, web server user).ls: Lists files in a directory./var/www: The directory path to list.
Run a Command with Root’s Login Environment
Example Usage:
sudo -i
What it does: Starts a root login shell, loading root user's environment variables and working directory.
Command-line Arguments Explained:
sudo: Grants elevated privileges.-i: Simulates an initial login shell for the target user (default is root).
Edit Files with Elevated Privileges
Example Usage:
sudo nano /etc/hosts
What it does:
Opens the /etc/hosts file in nano editor with root privileges for editing.
Command-line Arguments Explained:
sudo: Grants elevated privileges.nano: Command-line text editor./etc/hosts: File to open and edit.
Run a Command Without Prompts for Password (If Permitted)
Example Usage:
sudo -n systemctl restart apache2
What it does: Attempts to restart Apache2 service without prompting for a password. If password is required, it fails immediately.
Command-line Arguments Explained:
sudo: Grants elevated privileges.-n: Non-interactive; do not prompt for a password.systemctl: Service management command.restart: Subcommand to restart a service.apache2: The service name.
Run a Command and Preserve Environment Variables
Example Usage:
sudo -E env | grep PATH
What it does: Preserves the current user’s environment variables while executing the command and displays the PATH variable.
Command-line Arguments Explained:
sudo: Grants elevated privileges.-E: Preserves user's environment variables.env: Displays current environment.|: Pipes output to another command.grep: Searches for matching text.PATH: Text to search for.
Run a Command as Another Group
Example Usage:
sudo -g admin whoami
What it does:
Runs whoami with group privileges of admin.
Command-line Arguments Explained:
sudo: Grants elevated privileges.-g: Specifies group to execute command with.admin: Target group.whoami: Shows current effective username.
Display Available sudo Permissions
Example Usage:
sudo -l
What it does: Lists the commands the current user is allowed (or not allowed) to run with sudo.
Command-line Arguments Explained:
sudo: Grants elevated privileges.-l: Lists privileges or checks a specific command.
Run a Command in Background with Elevated Privileges
Example Usage:
sudo bash -c "apt update && apt upgrade -y" &
What it does: Runs a sequence of commands as root in a background process.
Command-line Arguments Explained:
sudo: Grants elevated privileges.bash: Executes commands in bash shell.-c: Runs the specified string as a command."apt update && apt upgrade -y": Command string to execute.&: Runs the process in the background.
Read a File with Elevated Privileges (Without Editing)
Example Usage:
sudo cat /etc/shadow
What it does:
Displays contents of the /etc/shadow file, which normally requires root access.
Command-line Arguments Explained:
sudo: Grants elevated privileges.cat: Displays file contents./etc/shadow: File containing system password hashes.
Execute Multiple Commands via sudo
Example Usage:
sudo sh -c "mkdir /opt/myapp && chown user:user /opt/myapp"
What it does:
Runs multiple commands as root using sh -c.
Command-line Arguments Explained:
sudo: Grants elevated privileges.sh: Invokes shell interpreter.-c: Executes command string."mkdir /opt/myapp && chown user:user /opt/myapp": Combined shell commands.
Suppress sudo Warnings and Messages
Example Usage:
sudo -s --prompt="" ls /root
What it does: Runs a command with a custom (empty) password prompt, suppressing default messages.
Command-line Arguments Explained:
sudo: Grants elevated privileges.-s: Runs an interactive shell with root privileges.--prompt="": Sets a custom password prompt (empty in this case).ls: Lists files in a directory./root: Target directory.
Run sudo with a Timeout Override (Custom Password Cache Duration)
Example Usage:
sudo -v
What it does: Updates or verifies cached credentials, extending the sudo authentication timeout.
Command-line Arguments Explained:
sudo: Grants elevated privileges.-v: Validates cached credentials (refreshes timeout).
Terminate Cached Credentials
Example Usage:
sudo -k
What it does: Invalidates the user’s cached sudo credentials, forcing password entry next time.
Command-line Arguments Explained:
sudo: Grants elevated privileges.-k: Kills cached credentials.
Run Command with Debugging Information
Example Usage:
sudo -D9 ls /root
What it does:
Executes ls /root with maximum debug output to help troubleshoot sudo configuration.
Command-line Arguments Explained:
sudo: Grants elevated privileges.-D9: Enables debugging at level 9 (highest).ls: Lists files in a directory./root: Target path.
