Run a shell script as another user that has no password

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

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.

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>

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

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.

You can use sudo to do this. First, you need to modify the /etc/sudoers file to add a rule that allows the hudson user to become the other user for the script in question. Let's assume you have a user1 account that needs to run /usr/local/bin/my_script.sh.

Run visudo to modify the sudoers file. Then, use the following sudo command to run the script from hudson.

It's very important that you use visudo to modify the sudoers file in order to check the file for errors before putting it in place. Also, I'd suggest a quick read through man sudoers in order to clearly understand what the above does before adding it to your configuration.

I have created few users without password using

sudo adduser --gecos "" --disabled-password --no-create-home user1
sudo adduser --gecos "" --disabled-password --no-create-home user2

To confirm please check

% sudo cat /etc/shadow | grep user
user1:*:19022:0:99999:7:::
user2:*:19022:0:99999:7:::

I have written a shell script named testing.sh like:

#!/bin/bash

whoami
id

Now I am going to run this script as different users who do not have any password.

$ sudo runuser -u user1 -- bash testing.sh
user1
uid=1001(user1) gid=1001(user1) groups=1001(user1)
$ sudo runuser -u user2 -- bash testing.sh
user2
uid=1002(user2) gid=1002(user2) groups=1002(user2)

root@localhost:/# su - johndoh -c "whoami"
johndoh
root@localhost:/# su - johndoh -c "echo \"hi $(whoami)\""
hi root
root@localhost:/# su - johndoh -c "echo \"hi \$(whoami)\""
hi johndoh
root@localhost:/#

I use "ssh" pointing to the same local machine. This enables me to run the shell script or command passwordless.

ssh target-user@localhost script-to-execute

First, I make sure the host-user saved his public key to the target user (in the same machine). Then I execute the ssh command I showed above.

The result, is a command/script run as the target user, without even entering a password.

sudo -u <user> <command>