Linux root execute as user

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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su options — running command as another user

I was wondering how to run a command as another user from a script. I have the script’s owner set as root. I also have the following command being run within the script to run the command as the hudson user:

For other googlers: some users might have this ability disabled on purpose. You can run sudo cat /etc/passwd | grep user-abc . If you see something like this: user-abc:x:994:994::/home/user-abc:/bin/false then it won’t work. That’s because the last part » /bin/false » means that there is no shell for that user.

2 Answers 2

$ su --help Usage: su [options] [LOGIN] Options: -c, --command COMMAND pass COMMAND to the invoked shell -h, --help display this help message and exit -, -l, --login make the shell a login shell -m, -p, --preserve-environment do not reset environment variables, and keep the same shell -s, --shell SHELL use SHELL instead of the default in passwd 

And some testing (I used sudo as I don’t know the password for the nobody account)

$ sudo su -c whoami nobody [sudo] password for oli: nobody 

When your command takes arguments you need to quote it. If you don’t, strange things will occur. Here I am —as root— trying to create a directory in /home/oli (as oli) without quoting the full command:

# su -c mkdir /home/oli/java oli No passwd entry for user '/home/oli/java' 

It’s only read mkdir as the value for the -c flag and it’s trying to use /home/oli/java as the username. If we quote it, it just works:

# su -c "mkdir /home/oli/java" oli # stat /home/oli/java File: ‘/home/oli/java’ Size: 4096 Blocks: 8 IO Block: 4096 directory Device: 811h/2065d Inode: 5817025 Links: 2 Access: (0775/drwxrwxr-x) Uid: ( 1000/ oli) Gid: ( 1000/ oli) Access: 2016-02-16 10:49:15.467375905 +0000 Modify: 2016-02-16 10:49:15.467375905 +0000 Change: 2016-02-16 10:49:15.467375905 +0000 Birth: - 

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Is it possible for root to execute a command as non-root?

I am actually executing a CLI program as a non-root user. I have set the sticky bit on and I am using setuid, so the program runs with root privileges. Now I am using system() within the program to invoke a GUI app. But I don’t want to run it as root, so I want to temporarily drop root privileges only for that call.

Yes that is how the first program for each user is run. The first process on the system is run as root. There are a lot of ways to drop privilege, including all the ways that can escalate privilege, plus some more.

4 Answers 4

A portable solution would be:

However, as google-chrome is requiring X11 access, this will likely fail unless you unsecured it, which would be a very bad idea, especially while running as root.

If X11 tunelling/forwarding is allowed, a better way would be

ssh -X abc@localhost google-chrome 

ssh -Y abc@localhost google-chrome 

@Steve Using su abc -c google-chrome will likely fail in the first place because abc cannot use root’s session, .Xauthority being unreadable for abc .

Short answer: «Yes, this is possible».

if you like to execute a non-X application then just use the following command:

If you like to run some X application as another user but with your own desktop first you need to create a helper script, that will make your life simpler

and using your favorite text editor create a file ~/bin/xsudo as follows:

#!/bin/bash # (C) serge 2012 # The script is licensed to all users of StackExchange family free of charge # Fixes/Enhancements to the script are greatly appreciated. # # SUDO_ASKPASS has to be set to the path of ssh-askpass # fix the following two lines if your distribution does not match this autodetection . /etc/profile.d/gnome-ssh-askpass.sh export SUDO_ASKPASS="$" SUDOUSERNAME="$1" shift xauth nlist "$"|sudo -HA -u $SUDOUSERNAME env --unset=XAUTHORITY \ bash -c "xauth nmerge - ; $*" 

and use it the same way as sudo but without any switches:

P.S. Starting xsession from the root account is strongly discouraged!

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