Running Commands as Superuser with sudo

To repeat the last command as an administrator, run sudo !! and enter the password. For example, a user without administrative privileges cannot create a directory under the /etc/ directory. To create it, run sudo !!.

> mkdir /etc/test/
mkdir: cannot create directory ‘/etc/test/’: Permission denied

> sudo !!
sudo mkdir /etc/test/
[sudo] password for root:

> ls -alrt /etc  | grep test
drwxr-xr-x 1 root root        0 Apr 20 12:48 test

To run package management commands as an administrator, add sudo before the command:

> sudo zypper [--GLOBAL-OPTIONS] <COMMAND> [--COMMAND-OPTIONS] [ARGUMENTS]

For example, to install the Docker CE containerization platform from its official package repository, run the following commands with sudo:

> sudo zypper addrepo https://download.docker.com/linux/suse/docker-ce

> sudo zypper refresh

> sudo zypper search docker-ce

> sudo zypper install docker-ce

You do not need to add sudo before zypper commands that do not modify the system, or provide privileged access to information. For example, you can list the repositories for the installed software packages on your system without using sudo:

> zypper lr

In systems that use systemd for managing services, you can use the systemctl command with sudo. For example, to restart the Apache Web Server service, run:

> sudo systemctl restart apache2

You do not need to add sudo before systemctl commands that do not modify the system, or provide privileged access to information. For example, you can display the status of Network Manager without using sudo:

> systemctl status NetworkManager
● NetworkManager.service - Network Manager
     Loaded: loaded (/usr/lib/systemd/system/NetworkManager.service; enabled; vendor preset: disabled)
    Drop-In: /usr/lib/systemd/system/NetworkManager.service.d
             └─NetworkManager-ovs.conf
     Active: active (running) since DAY YYYY-MM-DD HH:MM:SS TIMEZONE; 1h 21min ago
       Docs: man:NetworkManager(8)
   [...]

To run the usermod command for modifying user accounts, use:

> sudo usermod [OPTION] USERNAME

For example, to set the number of days to 30 for permanently disabling the user account tux after password expiry, run:

> sudo usermod --inactive 30 tux

To change file and directory ownerships from the current owner to a new owner, use:

> sudo chown [OPTION] [OWNER:[GROUP]] FILE

For example, to give tux the ownership of files and subdirectories in the /home/test/tux-files directory, run:

> sudo chown tux /home/test/tux-files/ --recursive

You can test the change in ownership by running the following command:

> ls -alrt /home/test/tux-files/ --recursive

Instead of using the su command for switching to a different user and then running commands, you can use the sudo -s command. A shell run by the sudo -s command inherits the environment of the current user. The sudo -s command also offers a few privilege control measures.

To run a command as a different user, use:

> sudo -s -u USERNAME COMMAND

By default, the command runs from the directory of the previous user, because the target user inherits the environment of the previous user.

For example, to recursively list the files and subdirectories of the /home/test/tux-files/ directory as the target user tux, run:

> sudo -s -u tux ls -alrt /home/test/tux-files/ --recursive

When you use the sudo -s approach for running a command as a different user, the command is logged in your history.

When using the sudo -s command, the target user inherits the environment of the previous user. You can prevent it by using the sudo -i command, where the target user gets a clean environment and starts at their own $HOME directory.

To run a command as a different user with a clean environment, use:

> sudo -i -u USERNAME COMMAND

The sudo -i command runs the shell as an interactive login shell of the target user. As a result, there are shell startup scripts such as .profile and .bash_profile files.

For example, to list the files and subdirectories of the /home/test/tux-files/ directory as tux, run the following command:

> sudo -i -u tux ls -alrt /home/test/tux-files/

When you use the sudo -i approach for running a command as a different user, the command is logged in your history.