I have a HP Pavilion dv6000 series (dv6602 au) laptop. I want to upgrade BIOS. I only have ubuntu installed in my system. Is it possible to upgrade bios from ubuntu? Google search gave me some results but somewhere I read that recent updates are done from inside windows installation and not with a floppy.
Updating a BIOS from Ubuntu is only possible if the hardware manufacturer provides a custom tool that runs with Ubuntu or Linux.
If this is (likely) not the case then you need a BIOS update tool that is installed on a bootable external device (e.g. CD-ROM). In the best case an .iso file that can be written on your stick or CD from Ubuntu can be downloaded. Sadly, generating a bootable device is often done again from a Windows utility that does not run in Ubuntu. If you are lucky the manufacturer provides a DOS-based BIOS update utility that you can run after booting into DOS (or FreeDOS).
HP offers a utility to update BIOS from a bootable CD-R, however AFAIK this CD needs to be generated from within Windows. In this case, and if you are unable to extract the CD's image from the data provided otherwise, you unfortunately will have to burn your bootable BIOS update medium on another machine that runs Windows.
BIOS downloads from HP are restricted and require regsitration to their site. Therefore I am sorry that I can't give you a more precise advice on the procedures involved.