I want to know when "apt-add-repository" becomes mandatory to run in Ubuntu machine. Usually I used following two commands many times.
$sudo apt-get update
$sudo apt-get install
When the package you want install was not found. You need add link or folder ftp way on you repository .
After you can update and install
I have a png file which I want to reduce in size and dimension. Do we have any command in ubuntu/linux to achieve the same?
Thanks in advance and sorry for hiding my identity.
What is the relation of "apt-get install" with "apt-get update" ? What exactly "sudo apt-get update" does ?