By running
as root you will see that at 04:40 the "daily maintenance" will be carried out. There is also a weekly and monthly maintenance schedule, but I guess the 0440 is the time when you hear the hard drives rattling.
Look into the directory
/etc/cron.daily/ and you will see a couple of (script) files that are being run at that time. One of those is
slocate which makes a searchable index of all filenames on your hard disk, hence the disk activity. That is the database that gets queried when you run
for instance.
For any command that is run as a
cron job and that produces output, the cron daemon will capture that output and send it to the owner of the cron job (most of the times that will be root, but you can schedule your own cron jobs too) and it will be sent as an email. For cron to be able to send those emails and for you to read them, you should have the sendmail and nail packages (and optionally pine) installed (they get installed by default I think). Reading those emails is as simple as logging in as root, and starting
. You might have to get used to the sparse command line interface, so you could also try
which is a curses based mail client. You can even use Thunderbird if you're brave enough to run X Window as root.
Most of the standard cron jobs do not produce console output when they run and so they do not generate emails. The emails come when things go wrong however!
Hope this clarified it a little.
Eric
