I cannot understand that why setuid doesn't work!

I wrote a script updatedhcpd.sh to restart dhcpd service in which:
/etc/init.d/dhcpd restart
and I set this script setuid attribute like this:
-rwsr-xr-x 1 root root 38 Nov 23 11:44 updatedhcpd.sh

When I run this script as other user, it still fails with the following information:
Shutting down dhcpd: ./dhcpd: line 196: kill: (927) - Operation not permitted
./dhcpd: line 201: kill: (927) - Operation not permitted
rm: cannot remove `/var/run/dhcpd.pid': Permission denied

But it succeeds if I run this script as root. I think when I run this script as other
users, it will be given the root role automatically.

Who can tell me WHY setuid doesn't work here!?
I tried to give setuid to bash also:
chmod +s /bin/bash
but no use!

Thanks!

Henry

Linux ignores the suid bit on scripts. Use sudo.

Thanks! But sudo will prompt to ask for password. I don't like it because I want to
call it in a script. How to use sudo without password?

I solved this problem. By using the following command in the /etc/sudoers
user HOST_ALIAS=NOPASSWD:CMD_ALIAS

we can let any other user run the specified CMD_ALIAS without password.

Thanks to anyone helped me!