`sudo -u` in script still prompts for invoking user password

Question

I'm logged in as user1 and I have two scripts, script1 attempts to call script2 using sudo -u user2. My problem is that I'm still prompted to enter password for user1 although I'm specifying -u option for sudo. Here is my setup:

1. Script1:

   #! /bin/bash
   
   echo "Current user in script1:" $USER
   
   # Call script2
   sudo -u user2 /full/path/to/script2
   

2. Script2:

   #! /bin/bash
   
   echo "Current user in script2:" $USER
   
   # Execute command as user2
   some-command-that-works
   

3. Equivalent /etc/sudoers to the one I have:

   # /etc/sudoers
   #
   # This file MUST be edited with the 'visudo' command as root.
   #
   # See the man page for details on how to write a sudoers file.
   #
   
   Defaults        env_reset
   
   # Host alias specification
   
   # User alias specification
   
   # Cmnd alias specification
   
   # User privilege specification
   user1 ALL=(ALL:ALL) ALL
   
   
   # Allow members of group sudo to execute any command
   # (Note that later entries override this, so you might need to move
   # it further down)
   %sudo ALL=(ALL) ALL
   #
   #includedir /etc/sudoers.d
   
   # Don't ask for user2 password for script2
   user2 ALL= NOPASSWD: /full/path/to/script2
   
   # FYI: I experimented with the line below for group1 that user1 is a member of
   %group1 ALL= NOPASSWD: /full/path/to/script2
   

4. ls -blah output

   drwxrwsr-x 2 user1 group1 4.0K Oct 19 15:22 .
   drwxrwsr-x 7 user1 group1 4.0K Oct 18 18:48 ..
   -rwxrwxr-x 1 user1 group1  180 Oct 20 17:37 script1
   -rwx------ 1 user2 group1  166 Oct 20 16:29 script2
   

An example of my shell attempt to run script1:

user1@host1 /full/path/to/script1 $ script1
Current user in script1: user1
[sudo] password for user1:

Edit: This is on a server that I connect to with ssh. The server is running Debian 6.0.4 Squeeze

Answer 1

sudo -u <user> gives a user permission to run a command as the given user.

It is not the same as su - <user>, which switches you to the given user. su - <user> requires you to enter the password for the given user in order to open a session as that user.

sudo -u <user> requires the current users password unless the NOPASSWD: flag is given in the sudoers file.

To achieve your desired functionality add this to your sudoers file

%group1 ALL=(user2) NOPASSWD: /full/path/to/script2

This will allow group1 to run script2 as user2 without entering a password.