meant to say...
1. Force all machines to authenticate against ldap only! users which has been created in /etc/passwd will no longer be able to access the system except Root
change the following lines in /etc/nsswitch.conf
passwd: files ldap
shadow: files ldap
group: files ldap
to this
passwd: ldap files
shadow: ldap files
group: ldap files
2. How can I grant a regular user root permissions such as administrating user accounts for other users in our Linux network.
sudo is the best tool for this.
Here is an example that will grant all root privileges to the developers group
add the following line to /etc/sudoers
%developers ALL=(ALL) ALL
a user in the devlopers group just needs to type sudo then the command they want to run
example "sudo useradd foobar"
adding the following line will only allow bob to shutdown the server
bob ALL=/sbin/shutdown -h now
here is a quick how to on sudo
http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch09_:_Linux_Users_and_Sudo