Updatedb - what is it for?

[Gábor Iglói]

Hi!

My machine sometimes starts to work furiously on the hard drive. So
I'm curious why. I issued a "top" command and found that the updatedb
process is working at these times. I haven't meet this thing in
another distro (maybe it's there too but I didn't noticed it) - so I
would like to ask: what it is and what it is for? I tried man and
Google but still not clear what's good in it.