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

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80
votes
2answers
13k views

Why do we use su - and not just su?

I don't understand why su - is preferred over su to login as root.
87
votes
7answers
13k 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 ...
5
votes
1answer
184 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 ...
19
votes
2answers
11k 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 ...
10
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?
92
votes
6answers
28k 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 ...
14
votes
3answers
10k 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 - ...
7
votes
4answers
2k 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. ...
15
votes
1answer
1k 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, ...
2
votes
3answers
980 views

What mechanism prevents any user from accessing any other user's files via root?

On a multi-user system, what protects against any user accessing any other users files via root? As context, the question is based on my understanding as follows: There are two commands related to ...
3
votes
2answers
13k 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 ...
6
votes
4answers
3k 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 ...
5
votes
2answers
1k 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 ...
3
votes
3answers
1k 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
2k 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
1answer
264 views

How do you keep the password hidden when invoked during the su command?

This is the first time it has happened to me where I am using the su command and it actually displays the password on the terminal and doesn't stay hidden. Here is my code snippet: sshpass -p ...
0
votes
4answers
14k 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.
34
votes
7answers
22k views

What is the need for `fakeroot` command in linux

Why do we need fakeroot command at all? Can't we simply use the sudo or su commands? The man page says: fakeroot - run a command in an environment faking root privileges for file manipulation ...
12
votes
2answers
15k views

“su” with error “X11 connection rejected because of wrong authentication.”

As root, I'm connecting to a remote host to execute a command. Only "standarduser" has the appropriate id-file and correct .ssh/config, so I'm switching the user first: su standarduser -c 'ssh -x ...
7
votes
2answers
22k views

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 ...
4
votes
1answer
549 views

Why do I need to use newgrp or su (or logout and login again) to have new group memberships applied?

What is it that makes new group membership require a new login (or new login shell as started by su or newgrp) to be visible? Just running another bash (or whatever other shell) instance with --login ...
7
votes
1answer
7k 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 ...
5
votes
3answers
3k views

Why is the 'sudo' password different than the 'su root' password

On my personal machine, I often type sudo in front of certain commands in order to accomplish administrative tasks. I had hoped to avoid doing this throughout the day, by typing su root and providing ...
5
votes
2answers
2k views

how to ssh -Y and then su - <another user> and still forward X applications to your local machine

it is easy enough to 'fetch' (ie draw locally) a remotely running linux application: If I ssh -Y to the remote machine and run an application, that application will surely enough pop up in my local ...
4
votes
3answers
1k 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 ...
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 ...
4
votes
3answers
2k views

Automate login with sudo and su

I know the security risks, but I am performing this experiment/exercise on an old, seldom used *nix machine I have laying around the house. So doing this exercise will not bring any security risk to ...
3
votes
4answers
11k views

How to login as root from Bash and do stuff

This is my simple bash: cat test.sh #!/bin/bash echo "hello" su - root -c /path/to/script.sh <<EOF password EOF whoami echo "good bye" But I get this error: ...
2
votes
0answers
120 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 ...