How do I edit the update.conf at /etc/update.conf to run every day on Ubuntu? This would enable me to use locate with a very recent database.

I read this:

default setting, updatedb, it has been in /etc/cron.daily and its name
is slocate.cron if you want to run updatedb on startup, you can add
the line updatebd to the file /etc/rc.d/rc.local.

In FC4 you must edit the file /etc/updatedb.conf and set
DAILY_UPDATE=yes.

But that is for Fedora.