nologin on Linux

--- Friends, I have a server Conectiva Linux 6.0. Sometimes I need to do some maintenance on the server and ask for my deslogarem users (the users use Windows 9x OS), but unfortunately they do not always deslogam and I'm stuck with the server in the air.
I wonder how do I block user login until I finish maintenance.
Note I read in a book that was enough to create a file called nologin in / etc and put there any message. After completion of maintenance, was sufficient to delete the file that the blockade would be disabled. However, I tried to do this but could not.

--- Yeah this file works, but you should be with the pam module enabled otherwise it's useless!
Type authconfig to check and see if it is enabled pam!
Flw
--- Dear
DarkWarrior18, I typed the command authconfig as you suggested me, but he opened a setup screen where it shows me the authentication options:
(*) files password () NIS


[*] Use Shadow Passwords
[*] Use MD5 Passwords
After that I leave this option the following message appears: Shutting down NIS services
< BR> How do I make this file [nologin] work right
Can you help me