How do I run Updatedb everyday?

From http://manpages.ubuntu.com/manpages/oneiric/en/man8/updatedb.8.html

updatedb is usually run daily by cron(8) to update the default database.

Check /etc/cron.daily. It should be there.

---

/etc/cron.daily$ ls *loc*    
mlocate

In addition to Rinzwind answer

updatedb is usually run daily by cron(8) to update the default database.

Now back to your demand:

if you want to run updatedb on startup

you can use cron for this job, run the command:

sudo crontab -e

Add the following:

@reboot /usr/bin/updatedb

Save and exit.

Now this ensures that you'll update the mlocatedb on every startup of your system, in addition to its scheduled everyday.

You can comment the line containing mlocate in /etc/cron.daily to stop the usual schedule everyday.