How to use the command 'sudo' (with examples)

The sudo command allows a user to execute a single command as the superuser or another user. This can be useful in situations where elevated privileges are needed to perform certain tasks or access specific files.

Use case 1: Run a command as the superuser

Code:

sudo less /var/log/syslog

Motivation: Running the less command with sudo allows a regular user to view the contents of the /var/log/syslog file, which is typically only accessible by the superuser. This can be useful for troubleshooting or inspecting system logs.

Explanation:

• sudo: Specifies that the following command should be executed with superuser privileges.
• less /var/log/syslog: The command to be executed, in this case, less is used to view the contents of the /var/log/syslog file.

Example output: The output will display the contents of the /var/log/syslog file, allowing the user to read the system logs.

Use case 2: Edit a file as the superuser with your default editor

Code:

sudo --edit /etc/fstab

Motivation: By using sudo --edit, a user can open and edit files that require superuser privileges, such as system configuration files like /etc/fstab. This ensures that the necessary permissions are granted to make changes to these files.

Explanation:

• sudo --edit: Runs the default text editor with superuser privileges.
• /etc/fstab: The file path of the file that needs to be edited.

Example output: The user’s default text editor will open, allowing them to modify the contents of the /etc/fstab file.

Use case 3: Run a command as another user and/or group

Code:

sudo --user=user --group=group id -a

Motivation: This use case is helpful when the need arises to execute a command as a specific user and/or group. It provides the flexibility to run commands with different user and group contexts, which can be especially useful in multi-user environments.

Explanation:

• sudo --user=user: Specifies the user under which the command should be run.
• --group=group: Specifies the group under which the command should be run.
• id -a: The command to be executed, in this case, id -a is used to display the user and group information.

Example output: The output will show the user and group information of the specified user and group, providing an overview of their identities.

Use case 4: Repeat the last command prefixed with sudo

Code:

sudo !!

Motivation: Using sudo !! allows the user to repeat the last command they executed, but this time with superuser privileges. This can be useful when a command fails due to insufficient permissions, and the user wants to immediately re-run it with elevated privileges.

Explanation:

• sudo: Specifies that the following command should be executed with superuser privileges.
• !!: A shell history expansion that represents the last command executed.

Example output: The last executed command will be repeated, this time with superuser privileges.

Use case 5: Launch the default shell with superuser privileges and run login-specific files

Code:

sudo --login

Motivation: This use case is useful for starting a new shell session with superuser privileges, allowing the user to perform administrative tasks. Running login-specific files such as .profile or .bash_profile ensures that any customizations or environment variables are set correctly.

Explanation:

• sudo --login: Launches the default shell with superuser privileges and executes login-specific files.

Example output: A new shell session will be started with superuser privileges, and any login-specific files will be executed, setting up the environment accordingly.

Use case 6: Launch the default shell with superuser privileges without changing the environment

Code:

sudo --shell

Motivation: In some cases, it may be necessary to access the superuser shell without altering the current environment. By using sudo --shell, the user can open a new shell session with superuser privileges while keeping the environment variables intact.

Explanation:

• sudo --shell: Launches the default shell with superuser privileges without modifying the environment.

Example output: A new shell session will be started with superuser privileges, with the user’s existing environment variables unchanged.

Use case 7: Launch the default shell as the specified user, loading the user’s environment and reading login-specific files

Code:

sudo --login --user=user

Motivation: This use case allows the user to launch a new shell session as a different user, while loading the specified user’s environment and executing any login-specific files. This can be helpful when it is necessary to work with a different user’s configurations or access files restricted to that user.

Explanation:

• sudo --login: Launches the default shell with superuser privileges and executes login-specific files.
• --user=user: Specifies the user under which the shell session should be launched.

Example output: A new shell session will be started with superuser privileges, using the specified user’s environment and executing any login-specific files.

Use case 8: List the allowed (and forbidden) commands for the invoking user

Code:

sudo --list

Motivation: By using sudo --list, a user can see a comprehensive list of commands that they are allowed or forbidden to run with superuser privileges. This is useful for understanding the user’s permissions and ensuring that they have the necessary access to perform specific tasks.

Explanation:

• sudo --list: Lists the allowed and forbidden commands for the invoking user.

Example output: The output will display a list of commands that the user is allowed or forbidden to run with sudo privileges, providing them with an overview of their permissions.

Conclusion:

The sudo command is a powerful tool that allows users to execute commands with elevated privileges. It enables a variety of use cases, such as running commands as the superuser, editing system files, executing commands as different users/groups, and more. By understanding the different use cases and their corresponding syntax, users gain greater control over their system and can perform administrative tasks more easily.