I have two users as follows
user: srvur1 group: hmadmin
user: srvur2 group: hmuser, hmadmin

The user 'srvur2' is a part of multiple groups. His primary group is 'hmuser'.

I have the following entry in /etc/sudoers
%hmadmin ALL=(ALL) NOPASSWD: ALL

With this entry the user 'srvur1' is able to execute sudo without password. But when 'srvur2' tries to sudo, it asks for password.

I want only certain users of 'hmuser' group to have sudo access, so I am trying to give them access by adding those users to 'hmadmin' group also, but this is not working.

I dont want to add the user 'sprur2' to /etc/sudoers as I have many servers and users, and managing the sudoers file would get difficult.

Is it possible to give sudo access to a user by adding him to a group which has sudo access? Does sudo work when a user is in multiple groups?

Please help

It should. Try to uncomment the wheel line
and add the users to the wheel group. Shouldn't be any different than your group, but it is much simpler and less likely that you will make a typo.

I don't think using the wheel group is a good idea; its effectively the root group.

If this is going to be used in a script, try newgrp http://linux.die.net/man/1/newgrp

Not if you edit the line granting the wheel group certain access.

I believe your syntax in your sudoers file could be wrong.

If you want to give a group sudo rights with NOPASSWD, it should be:

%GROUPNAME ALL = NOPASSWD:COMMANDS

So in your case:

%hradmin ALL = NOPASSWD: ALL

Try that.