Dear Lina: Running a shell script with the cron daemon

[ Thanks to Matthew Cunningham for this
link. ]

“Dear Lina,
I want my roommate to be able to power down my computer. At the
same time I don’t want to give him root access to my machine. Any
suggestions for what I can do?..”

“Dear Lina,
The new system administrator at my job (and my boss) gave me a
shell script called “clean_logs”, and told me to run it on my Linux
machine with the cron daemon. How on earth do I do that?