sudo dpkg -i avast-linux-home-edition-1.3.0.deb
step 3 : To start using avast antivirus software, You need to Register with avast here to get a free license key (Don’t worry it’s free!). The license key will be delivered to your email address within 24 hours (usually within a couple of hours).
step 4 : Start the program and enter the license key.
step 5 : To achieve database updating (in my Ubuntu 12.04), the treatment according to Error message in Avast! with the value
according to the comment by 'pbhj' is necessary. That’s all!