su is a utility to run a shell or other command as another user (root by default).

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80
votes
7answers
10k views

Which is the safest way to get root privileges: sudo, su or login?

I would like to have the root account in safety even if my unprivileged user is compromised. On Ubuntu you can only use sudo for "security reasons" by default. However I am not sure it is any safer ...
67
votes
2answers
7k views

Why do we use su - and not just su?

I don't understand why su - is preferred over su to login as root.
5
votes
1answer
112 views

How to allow to run su instantly after I added the user to the appropriate group

I have the su executable with the following permissions: bash-4.2# ls -la /bin/su -rws--s--- 1 root wheel 59930 Sep 14 2012 ./su When I am logged in as a user, not in the wheel group and try to ...
9
votes
2answers
3k views

When do su and sudo use different passwords?

I am able to run anything using sudo; my password is accepted. But whenever I try to do su from a shell, it fails with: su: incorrect password What can the problem be?
9
votes
2answers
4k views

.bash_profile not sourced when running su

I have a user, say user1, which has modifications to its .bash_profile, one of them changing the PATH, e.g.: export PATH=/some/place:$PATH. This change works fine if I log on as user1 or do a su - ...
10
votes
1answer
835 views

What's the difference between sudo su - and sudo su --

When I am working on our RHEL machines, I use sudo su - to switch to being root. One day, a typo meant I typed sudo su -- instead - it seems to me that everything was the same as with a single hyphen, ...
7
votes
4answers
1k views

sudo permission denied but su grants permission

this is the first occurrence where su was required for me. I read an article about changing the value in /sys/devices/virtual/backlight/acpi_video0/brightness to alter my laptop's screen brightness. ...
65
votes
5answers
19k views

Where did the “wheel” group get its name?

The wheel group on *nix computers typically refers to the group with some sort of root-like access. I've heard that on some *nixes it's the group of users with the right to run su, but on Linux that ...
15
votes
2answers
6k views

su vs sudo -s vs sudo bash

What is the difference between the following commands: su sudo -s sudo bash I know for su I need to know the root password, and for sudo I have to be in the sudoers file, but once executed what is ...
5
votes
2answers
940 views

Alternative to su/sudo on barebone system

I'd like to run some unit tests in a barebone chroot jail on Solaris. There's no su or sudo, and a copy of su (with libpam.so.1) just returns exit code 1 without any output, with or without ...
2
votes
2answers
284 views

Cannot connect to X server :0.0 as superuser

When I am online, I get following error and the tool does not start: [root@dhcppc9 lin64]# ./ise No protocol specified _pn: cannot connect to X server :0.0 But everything is OK when I am not a ...
5
votes
4answers
772 views

Why can't we execute a list of commands as different user without sudo?

This question has been asked in a different way in other forums. But there has not been a decent explanation why you can't do the below in bash. #!/bin/bash command1 SWITCH_USER_TO rag command2 ...
3
votes
3answers
723 views

linux launch script /etc/init with a specific user

I've created a script in /etc/init/mms-agent.conf : start on runlevel [2345] stop on runlevel [06] exec /usr/bin/env python /home/mms/mms-agent/agent.py >> /home/mms/agent.log 2>&1 ...
2
votes
3answers
1k views

Switching to superuser while shell script is running

I have a shell script that contains the following lines: CURRENT_USER=${USER} echo $CURRENT_USER su echo switch to `who am i` Once the 2nd line is executed, the shell prompts me to enter the root ...
0
votes
4answers
5k views

Is there a difference between sudo su - root and sudo -u root -H /bin/bash?

Like title says, is there a difference between these two commands : sudo su - root sudo -u root -H /bin/bash I'm using GNU/Linux, if that makes a difference.
3
votes
2answers
3k views

su vs su - (on Debian): why is PATH the same?

I know what should be the difference between su and su -, but in my system (debian testing) for example PATH is the same: [root]# su [root]# echo $PATH ...
3
votes
2answers
898 views

`$XAUTHORITY` appears from 'nowhere' on su+tmux

When I switched from su+bash to su+tmux+zsh I noticed that I get $XAUTHORITY variable defined as /root/.xauthXXXXXX where XXXXXX are 6 random alphanumeric characters. With previous configuration X ...
7
votes
1answer
5k views

How to run a GUI program as a different user (Debian)?

Using a terminal, I can change the running user with su and sudo — but how can I do that by clicking on an icon/shortcut on the desktop/start menu? If I have to be root to execute I will be asked ...
2
votes
0answers
86 views

Understanding getlogin spoofing

My question is in three (or so) related parts: 1) My understanding is that getlogin() will effectively return the auid associated with the process and so isn't actually changable by the user. Is that ...