i can use Wake-On-Lan to power on all my clients, How can i shutdown all my clients with my RedHat 7.3 Server. Thank!.

OK, I just use crontab and the /sbin/shutdown command. edit your crontab file as such.. 30 17 * * * * root /sbin/shutdown -h -T sec 5 "Automatic SHUTDOWN in progress, Save your work!!" Every afternoon at 5:30, the machine issues the shutdown command, displaying a message on the terminal every minute until shutdown. I know that is a rather lame way of controlling 20 terminals, but, I did change that. I wrote a little script to be called from /etc/crontab to wget an update script from our webserver ever hour. Then the script executes all of the commands I tell it. Like, copy a new crontab to /etc and restart the cron daemon, so you can adjust the shutdown times from one file, on your webserver (or wherever you want to put it). There is probably a better way of doing this, and I too am open to suggestions. Hope this helps a little.