I've been playing on an Ubuntu machine recently which was not set to automatically update.  The following commands will acquire the updates and install them.  First run:

sudo apt-get update

You will be prompted for an elevated account password which will then be followed by a list of sites, sources and packages scrolling up your screen.  At the end, you should see "Reading package lists... Done" at which point, run the following:

sudo apt-get dist-upgrade

You are likely to receive a message and question regarding disk space usage for the new updates, select Y if you have enough disk space.  After a minute or many minutes (depending on the last time you updated), you will be returned to the command prompt.  Your updates have been completed.