I want to install kde live 12.3 how small is needed to be install?
You want to install openSUSE with KDE to a USB stick?? Is that right? And you want to know how small a stick you can use? Right?
Your question is really not too clear.
BTW I don’t recommend usong a Thumb drive to actuall install a OS on. The reason is that a Thumb is not the same a SSD and the memory will ware out quickly. Also they are relatively slow especial at write operations. So please say what you actually want to accomplish.
Can I use a 4gb to install kde live or gnome live? or dose it need to be bigger?
Ok now I understand. 4 gig is plenty Would work on 2 gig for the live DVD isos