Running Commands as Superuser with sudo

Running Commands as Supe-

ruser with sudo

WHAT?

Learn about the basic concepts of sudo and how to use it as a regular

user.

WHY?

Certain commands require administrator privileges. To run a command

with administrator rights, the sudo command can be used.

EFFORT

It takes you up to 20 minutes to read through this article. If you have a

specific question, you can jump directly to the respective chapter.

GOAL

Understanding the basic concepts of sudo and running commands

with sudo for certain use cases.

REQUIREMENTS

root or sudo privileges. These are only available if you are the

administrator of the system. For more information, refer to Sec-

tion1, “Basic concepts of sudo”.

The sudo package needs to be installed. This package is available

on SUSE Linux Enterprise Server by default.

Publication Date: 08Aug2024

1 Running Commands as Superuser with sudo

Contents

1 Basic concepts of sudo 3

2 Running a command prefaced with sudo 5

3 Common sudo commands 6

4 Diﬀerence between sudo and su 9

5 Legal Notice 9

A GNU Free Documentation License 10

2 Running Commands as Superuser with sudo

1 Basic concepts of sudo

Learn about the basic concepts of sudo and how it works on SUSE Linux Enterprise

Server systems.

sudo is a Linux command that is used to temporarily execute programs as another user. It is

the abbreviation for substitute user and do and borrows the privileges of another user,

for example, the root user. This way, sudo helps you accomplish system administration tasks

without logging in as root .

1.1 sudo on Linux systems in general

As a regular user on Linux, you have reduced permissions that are sufficient for most of the

tasks. The root user is the Linux superuser and the equivalent to the administrator.

sudo allows specified (non- root ) users or a group of users to run privileged tasks, like calling

system functions as root or another user. Through a configuration le, the system administrator

can control which users are allowed to run sudo commands and for which tasks.

1.2 sudo on SUSE Linux Enterprise Server systems

For security reasons, all SUSE Linux Enterprise Server systems separate the regular user from

the root user. As a regular user, you cannot write to system directories or install programs. Any

user with access to the root password can gain these privileges and accidentally or maliciously

break the system.

For example, you are logged in as a regular user and accidentally browse to a malicious website.

An attacker cannot install malware on your system behind your back, as you are logged in as a

regular user, means without any administrative permissions.

As explained above, it is not recommended to be logged in as root user permanently for security

reasons. A safer approach is to stay logged with your regular user and running a restricted

command prefaced with sudo .

Note: sudo requires administrator rights

On a single-user machine, where you have set your own root password, you have the

required rights to administrate your system by using the sudo command and to configure

sudo settings yourself.

3 Running Commands as Superuser with sudo

For more information about how to configure sudo , refer

to https://documentation.suse.com/smart/systems-management/html/sudo-configure-su-

peruser-privileges/index.html .

In a multi-user environment, such as in companies, the sudo privileges are managed by

a system administrator and the permissions of the root user can be restricted. You may

not be allowed to change certain system directories or les, even when executing the

command with sudo .

1.3 How sudo works

When running a command prefaced with sudo , the system asks you for the password of the

root account. After successful authentication, the command is executed with superuser priv-

ileges.

Depending on the sudo configuration, the elevated privileges persist for a certain period of time

and as long as you are working in the same terminal session. So you do not need to provide a

password again when running another sudo command.

To run a command with sudo , this syntax is used:

> sudo [command]

The following example explains how the sudo command is used to open the YaST Control Center

in the terminal directly. To open YaST, administrator rights are needed and therefore, it only

works with the sudo command.

EXAMPLE1:OPENING THE YAST CONTROL CENTER WITH sudo

> yast

Absolute path to 'yast' is '/usr/sbin/yast', so running it may require superuser

privileges (eg. root).

> sudo yast

[sudo] password for root:

When only the yast command is entered, the system returns that root privileges

are required.

Starting the yast command with sudo prompts you for the root password. The

password is not shown during input, neither as clear text nor as masking characters.

After successful authentication, the YaST Control Center is opened.

4 Running Commands as Superuser with sudo

The elevated privileges persist for a certain period of time, so you do not have to provide

a password again for the next sudo command.

2 Running a command prefaced with sudo

As a regular user, you can run any command as root by adding sudo before it.

This prompts you to provide the root password. If authenticated successfully, this

runs the command as root .

When running a command prefaced with sudo , the system asks you for the password of the

root account. After successful authentication, the command is executed with superuser priv-

ileges.

Depending on the sudo configuration, the elevated privileges persist for a certain period of time

and as long as you are working in the same terminal session. So you do not need to provide a

password again when running another sudo command.

PROCEDURE1:RUNNING A COMMAND PREFACED WITH sudo

The following procedure describes how to use the sudo command to copy a le into a

directory where only the root user has editing rights.

Open a terminal and create a test le with:

> touch test.txt

Try to copy the le into the /usr/local/bin/ directory with:

> cp test.txt /usr/local/bin

The terminal returns, for example:

cp: cannot create regular file '/usr/local/bin/test.txt': Permission denied

This message also appears if the required privileges were not granted to sudo .

Now, enter the same command prefaced with sudo :

> sudo cp test.txt /usr/local/bin

You are prompted to enter the root password. Note that the password is not shown during

input, neither as clear text nor as masking characters.

5 Running Commands as Superuser with sudo

[sudo] password for root:

After successful authentication, the test le is copied to /usr/local/bin .

You have run your rst sudo command.

3 Common sudo commands

By adding sudo before any command, you can run commands with elevated per-

missions. You can also run commands as another user and use their environment

variables.

This section provides examples of common commands that often require administrative privi-

leges.

Repeat the last command 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

Manage packages using sudo and zypper

To run package management commands as an administrator, add sudo before the com-

mand:

> 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

6 Running Commands as Superuser with sudo

> 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

Manage system services using sudo and systemctl

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)

[...]

Modify a user account using sudo and usermod

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

Modify ﬁle and directory ownership using sudo and chown

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

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

7 Running Commands as Superuser with sudo

For example, to give tux the ownership of les 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

Run a command as another user using sudo -s

Instead of using the su command for switching to a different user and then running com-

mands, 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 les 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.

Run a command as another user with a clean environment using sudo -i

When using the sudo -s command, the target user inherits the environment of the pre-

vious 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 les.

For example, to list the les 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.

8 Running Commands as Superuser with sudo

4 Diﬀerence between sudo and su

Learn the difference between sudo and su commands and when to use which.

On Linux systems, you can preface a command with either sudo or su . Both let you execute

commands as root .

4.1 Characteristics of the sudo command

sudo allows you to run a command as root . Depending on the configuration, it does

not require you to enter the root password, but only the user's password. This way, no

sensitive information needs to be shared with all the other (regular) users.

With the sudo configuration le, the system administrator can control which users are

allowed to use sudo and restrict the usage to certain tasks.

sudo caches the password for a certain period of time. After this period, you are prompted

for the password again, when running another sudo command.

All commands executed with sudo are logged individually. The log le tracks date and

time, the user that ran the command, and the command itself.

4.2 Characteristics of the su command

su allows you to run a command as root but requires you to know the root password.

It cannot be configured to restrict access to certain users and tasks and elevate the privi-

leges for anyone who knows the root password.

The privileges are elevated for the entire terminal session. As long as you stay in the session,

you are not prompted for the password again.

Commands executed with su are not logged individually, as all actions can only be logged

with the user account.

5 Legal Notice

9 Running Commands as Superuser with sudo

Permission is granted to copy, distribute and/or modify this document under the terms of the

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10 Running Commands as Superuser with sudo

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11 Running Commands as Superuser with sudo

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12 Running Commands as Superuser with sudo

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13 Running Commands as Superuser with sudo

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14 Running Commands as Superuser with sudo

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15 Running Commands as Superuser with sudo

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16 Running Commands as Superuser with sudo

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17 Running Commands as Superuser with sudo

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ADDENDUM: How to use this License for your documents

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A copy of the license is included in the section entitled “GNU

Free Documentation License”.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the

“with...Texts.” line with this:

with the Invariant Sections being LIST THEIR TITLES, with the

Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other combination of the three,

merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these

examples in parallel under your choice of free software license, such as the GNU General Public

License, to permit their use in free software.

18 Running Commands as Superuser with sudo