Linux root command line

How do I run a command as the system administrator (root)

I need to run a command with administrative privileges. Someone said I should run a command as root. How do I do this?

4 Answers 4

The main two commandline possibilities are:

• Use su and enter the root password when prompted.
• Put sudo in front of the command, and enter your password when prompted.

Running a shell command as root

sudo (preferred when not running a graphical display)

This is the preferred method on most systems, including Ubuntu, Linux Mint, (arguably) Debian, and others. If you don’t know a separate root password, use this method.

Sudo requires that you type your own password. (The purpose is to limit the damage if you leave your keyboard unattended and unlocked, and also to ensure that you really wish to run that command and it wasn’t e.g. a typo.) It is often configured to not ask again for a few minutes so you can run several sudo commands in succession.

sudo service apache restart 

If you need to run several commands as root, prefix each of them with sudo . Sometimes, it is more convenient to run an interactive shell as root. You can use sudo -i for that:

$ sudo -i # command 1 # command 2 . # exit 

Instead of sudo -i , you can use sudo -s . The difference is that -i reinitializes the environment to sane defaults, whereas -s uses your configuration files for better or for worse.

For more information, see the sudo website, or type man sudo on your system. Sudo is very configurable; for example it can be configured to let a certain user only execute certain commands as root. Read the sudoers man page for more information; use sudo visudo to edit the sudoers file.

su

The su command exists on most unix-like systems. It lets you run a command as another user, provided you know that user’s password. When run with no user specified, su will default to the root account.

su -c 'service apache restart' 

The command to run must be passed using the -c option. Note that you need quotes so that the command is not parsed by your shell, but passed intact to the root shell that su runs.

To run multiple commands as root, it is more convenient to start an interactive shell.

$ su # command 1 # command 2 . # exit 

On some systems, you need to be in group number 0 (called wheel ) to use su . (The point is to limit the damage if the root password is accidentally leaked to someone.)

Logging in as root

If there is a root password set and you are in possession of it, you can simply type root at the login prompt and enter the root password. Be very careful, and avoid running complex applications as root as they might do something you didn’t intend. Logging in directly as root is mainly useful in emergency situations, such as disk failures or when you’ve locked yourself out of your account.

Single User Mode

Single user mode, or run-level 1, also gives you root privileges. This is intended primarily for emergency maintenance situations where booting into a multi-user run-level is not possible. You can boot into single user mode by passing single or emergency on the kernel command line. Note that booting into single-user mode is not the same as booting the system normally and logging in as root. Rather, the system will only start the services defined for run-level 1. Typically, this is the smallest number of services required to have a usable system.

You can also get to single user mode by using the telinit command: telinit 1 ; however, this command requires you to already have gotten root privileges via some other method in order to run.

On many systems booting into single user mode will give the user access to a root shell without prompting for a password. Notably, systemd -based systems will prompt you for the root password when you boot this way.

Other programs

Calife

Calife lets you run commands as another user by typing your own password, if authorized. It is similar to the much more widespread sudo (see above). Calife is more light-weight than sudo but also less configurable.

Op

Op lets you run commands as another user, including root. This not a full-blown tool to run arbitrary commands: you type op followed by a mnemonic configured by the system administrator to run a specific command.

Super

Super lets you run commands as another user, including root. The command must have been allowed by the system administrator.

Running a graphical command as root

PolicyKit (preferred when using GNOME)

Simply prefix your desired command with the command pkexec . Be aware that while this works in most cases, it does not work universally.

See man pkexec for more information.

KdeSu, KdeSudo (preferred when using KDE)

kdesu and kdesudo are graphical front-ends to su and sudo respectively. They allow you to run X Window programs as root with no hassle. They are part of KDE. Type

kdesu -c 'command --option argument' 

and enter the root password, or type

kdesudo -c 'command --option argument' 

and enter your password (if authorized to run sudo ). If you check the “keep password” option in KdeSu, you will only have to type the root password once per login session.

Other programs

Ktsuss (“keep the su simple, stupid”) is a graphical version of su.

Beesu is a graphical front-end to the su command that has replaced Gksu in Red Hat-based operating systems. It has been developed mainly for RHEL and Fedora.

Obsolete methods

gksu and gksudo are graphical front-ends to su and sudo respectively. They allow you to run X Window programs as root with no hassle. They are part of Gnome. Type

gksu command --option argument 

and enter the root password, or type

gksudo command --option argument 

and enter your password (if authorized to run sudo ).

gksu and gksudo are obsolete. They have been replaced by PolicyKit in GNOME, and many distributions (such as Ubuntu) no longer install them by default. You should not depend on them being available or working properly.

Manually via one of the shell-based methods

Use one of the methods in the «running a shell command as root section». You will need to ensure that neither the DISPLAY environment variable nor the XAUTHORITY environment get reset during the transition to root. This may require additional configuration of those methods that is outside the scope of this question.

Overall, this is a bad idea, mostly because graphical applications will read and write configuration files as root, and when you try to use those applications again as your normal user, those applications won’t have permission to read their own configurations.

Editing a file as root

It should be noted that sudo will only work if (1) it’s installed and (2) if your use is in the sudoers file and it allowed to perform the operation.

In either case, you will be prompted for the root password. For more information, see the manual page.

Since the question was not Linux specific, here’s how you achieve the same goal in Solaris 9+ (or Trusted Solaris 8):

Solaris, since version 9, has included a suite of tools affectionately referred to as RBAC, or Role Based Access Control.

The gist of RBAC is that through the granting of Authorizations and Rights, to Users and/or Role, or the granting of Roles to Users, you can create incredibly fine grained models for who can run what with which privileges.

Essentially, you identify authorization in /etc/security/auth_attr, then grant them to users or roles in /etc/user_attr.

You define profiles in /etc/security/prof_attr. You then associate commands with those profiles in /etc/security/exec_attr, followed by assigning those profiles to users in the /etc/user_attr file.

Once those things are done, you actually run pfexec to execute the command with privileged or authorizations that are granted to that user for that command.

The nice thing about RBAC is that there are no additional privileges granted to the command itself, or the user, only to the combination of user + command. So it’s safer than making a binary +s, or just using sudo to make a user be able to execute pretty much anything. (I know that you can lock down sudo, but in my experience most people don’t)

Another advantage of RBAC is that you can make root a role account, and assign that role to users who are able to become root with the ‘su’ command and the root password. The root user will also be able to log in in Single User Mode, which is better (in my opinion) than the Linux model where you can disable the root password passwd -d root , or lock the root account passwd -l root , both of which make logging in as root quite hard when something goes wrong.

Ben Rockwood has a great blog post on RBAC that can be read at Using RBAC on (Open)Solaris.

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How Do I Become a Root User in Linux

The root is the super-user account on Linux-based operating systems. The root user has all the rights that are necessary to perform administrative tasks or access some files, execute privileged commands, and much more. The root user is also referred to as a superuser or root.

In Linux, you can run privileged commands using the sudo keyword. However, sometimes it becomes a tedious act when you are doing administrative tasks and each command requires root privileges. To get rid of such a situation, become a root user and then execute commands.

This article provides various possibilities to become a root user on Linux.

How do I become a root user on Linux

As discussed earlier the root user has the necessary privileges to execute and perform various tasks on Linux-based systems. This section demonstrates Linux commands that can be used to become a root user on Linux.

How to use the sudo command to become a root user

The sudo command allows a normal user to perform the tasks that a superuser can do. Here, we provide the possible usages of the sudo command to become a root user.

Using the “sudo su –”

The `su` refers to switching the user and if the username is not provided, it will switch you to a root user, and the command provided below assists in this regard.

After successful authentication, it is noted that we are now switched to a root user.

Using the “sudo su”

The command written below will change the privileges to the root user.

Using the “sudo -i”

The command provided below will change the privileges to a root user.

The output shows that the dollar sign($) has been replaced by the pound key(#) which also directs that you are currently logged in using the root privileges.

Using “sudo -s”

The “-s” parameter enables the user to run the shell with a specific user. And if the username is not specified then the root (default) is considered.

How to use su command to become a root user

The su command allows you to switch the user to someone else by providing its username. However, if the name is not specified, the su command would allow you to execute the commands with root privileges.

There are various parameters that would allow you to become a root user.

Using “su –”

Using “su -l”

Using “–login”

It is observed from the above outputs that you are switched to the root user and can now perform the privileged tasks.

During the authentication of su command, you have to put the root password.

Note: In case you are unable to execute the above commands, you must set the password for root by using the following command.

Bonus Tip

Once you are logged in as a root user, it is recommended to check whether you are working with root privileges or not. To do so, the $LOGNAME variable would help, as the $LOGNAME contains the user you are currently logged in as.

For instance, we have tried to switch to the root user using the “su” command, and let’s check the logged-in user with the help of the following command.

The output shows that you are not logged in using the root privileges.

Conclusion

The root user is the ultimate boss of a Linux system, it can perform any task without any hurdle. This guide intends to explore the possible commands or ways to become a root user on Linux so that the frequent authentication hurdle can be avoided. Lastly, it is concluded that the sudo and su keywords are the main stakeholder to become a root user on Linux-based machines. The sudo requires the password of the currently logged-in user whereas the su requires the password of the target user.

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