I want to know whether there is any way I can use Emacs as Terminal in Ubuntu. Means, I want to do the basic works with Emacs that I usually do with Terminal in Ubuntu, like 'sudo apt-get update'. I'll write this command and it'll update my Ubuntu system. Is that possible?
You have a couple options, the perform the same basic function but there are some subtle differences. First you have M-term. This is a full fledged shell inside of an Emacs frame and responds the same as a terminal window and runs in it's own buffer. The issues I have with this is that you cannot switch buffers while the terminal is active, you must
Your other option is M-eshell. This is a seemingly mor lightweight option that runs on top of your current buffer and allows you to switch buffers and execute Emacs commands from the mini-buffer while using eshell.
You might want to read over this emacswiki page, has lots of good info on the topic.