# 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.