Run a shell script as another user that has no password

Question

I would like to run a script from the main ubuntu shell as a different user that has no password.

I have full sudo privileges, so I tried this:

sudo su -c "Your command right here" -s /bin/sh otheruser

Then I have to enter my password, but I am not sure if that script is now really running under that user.

How can I confirm that the script is really running under that user now?

Solution 1

You can do that with su or sudo, no need for both.

sudo -H -u otheruser bash -c 'echo "I am $USER, with uid $UID"' 

The relevant parts of man sudo:

-H   The -H (HOME) option requests that the security policy set
     the HOME environment variable to the home directory of the
     target user (root by default) as specified by the password
     database.  Depending on the policy, this may be the default
     behavior.

-u user     The -u (user) option causes sudo to run the specified
      command as a user other than root.  To specify a uid
      instead of a user name, use #uid.  When running commands as
      a uid, many shells require that the '#' be escaped with a
      backslash ('\').  Security policies may restrict uids to
      those listed in the password database.  The sudoers policy
      allows uids that are not in the password database as long
      as the targetpw option is not set.  Other security policies
      may not support this.

su can only switch user without providing a password if you are root. See Caleb's answer

You can modify the /etc/pam.d/su file to allow su without password. See this answer.

If you modified your auth file to the following, any user that was part of group somegroup could su to otheruser without a password.

auth       sufficient pam_rootok.so
auth       [success=ignore default=1] pam_succeed_if.so user = otheruser
auth       sufficient   pam_succeed_if.so use_uid user ingroup somegroup

Then test from terminal

rubo77@local$ su otheruser -c 'echo "hello from $USER"'
hello from otheruser

Solution 2

If you want to use su instead of sudo, I believe you can use something like this:

su - <username> -c "<commands>"

• - will simulate a login of the specified user
• -c tells it that you want to run a command

ps. Unfortunately I'm not able to install ruby using rvm with this method, but that's probably not related.

Solution 3

The answers above are really useful to me but to answer the actual question...

How can I affirm that the script is really running under that user now?-

Use:

ps -ef | grep <command-name>

The output should include your script and the actual user executing it. People on BSD-like systems, e.g. MAC can find similar information with:

ps aux | grep <command-name>

Solution 4

Make sure you switch to root user with command sudo su and then use the command

su user -s <command>

For example: su www-data -s bin/magento cache:clean

Solution 5

I had the same problem. Just type in the command screen -dmS testscreen this will create a detached screen on your non-sudo user account and then you can log it and check if this screen is there by screen -ls.

View more solutions

Comments

[rubo77]

Can you please add how to do it with just su too?

[IanVaughan]

This asks me for a password :-(

[IanVaughan]

I needed to add sudo to the beginning otherwise it asked me for my password.

[geirha]

@IanVaughan, With default configuration (of sudo), you will get asked for a password unless you run it as root. You can configure sudo to "allow user A to run cmd C as user B without requiring a password". See help.ubuntu.com/community/Sudoers

[Nate]

I'm prompted for a password when running this as root. Any suggestions?

[geirha]

@Nate, have you made some changes to the sudoers file. The default configuration allows root to run anything as anyone, without requiring a password.

[Victor]

WIll this change the HOME variable just for the command I run? (meaning that the next ones will be run as before)

[William]

Does this work for GUI applications?

[Samuel Åslund]

To use "su" you need the root password, the point of "sudo" is to avoid that. If you have the root password using "su" as above should work fine.

[xi.lin]

@Victor Yes, you can try sudo -H -u user bash -c 'echo ~'

[Dean Howell]

Linux users can use ps aux.

[Samuel Åslund]

@DeanHowell; True, but MAC users can not use "ps -ef" and the "ps aux" is BSD options, only available as a compatibility feature while the "ps -ef" is standardized Unix/POSIX options.

[Nam G VU]

This trigger password prompt for me too - even when I already config it not to with myuser ALL=NOPASSWD: ALL in sudo visudo

[geirha]

@NamGVU keep in mind that order matters. If your sudoers has a rule further down that sets other permissions for your user, or a group you're a member of, that will override your NOPASSWD rule.

[Nam G VU]

@geirha Thank u for the warning. My visudo content is very short and only a few line definin the NOPASSWD as above.

[ImranRazaKhan]

@geirha sudo -H not working on centos

[geirha]

@ImranRazaKhan how do you tell it isn't working?

[PLG]

"unfortunately I'm not able to install ruby using rvm with this method": when I used this command, the resulting path was bare (e.g., /bin:/usr/bin), so my command (similar to your rvm) wasn't found.

[WinEunuuchs2Unix]

You should show the actual line(s) that would be inserted into sudoers file.

[woodz]

and what about switching to a specific group?

[Nate T]

No simulation involved. Using su, you are performing a login. su literally stands for "switch user". sudo lets you mask yourself as the root user, whereas su lets you log in as that user (or any user so long as you have the appropriate passwod.) Using sudo su is like saying "Hey, this is the root account . Could you switch me to the root account?" That said, it still has it's place.

[Mohammed Noureldin]

This is the only solution that worked for me! Thanks!

[rubo77]

Can you elaborate runuser and the double hyphen --?