I want to be sure if automatic updates are enabled on Ubuntu 12.04 server.
How exactly can I check this?
And how can I disable automatic updates if it's enabled?
There is a package that can be used to do this for you.
or if unattended-upgrades already installed. Or you can checkout the Ubuntu docs
That is the package you need to install. Once its installed edit the files
In that file you can set how often you want the server to update.
The file should look like that. The 1 means it will update every day. 7 is weekly.
This files will let you chose what updates you want to make by choosing where apt can search for new updates and upgrades. ( My personal opinion on this is I would set it to security if this is a server )
Automatic Updates are enabled by default. If not, to enable automatic updates, just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command below.
For more information, and how to configure these updates, see Ubuntu Documentation
In server, you can also you can edit