Ubuntu – How to install just security updates from the command line

The Security Updates includes all the repositories (restricted, multiverse, etc.).

And the solution you say (which is useful and I recommend it) is only to receive Security Updates. But it doesn't include the partners security updates.

I hope I helped you.

My question is just about detecting the availability of security updates

Yes, that's doable with the caveat that the normal apt-get update will do a full refresh when you next run it (20 MB means it's doing that anyway).

• sudo sh -c 'grep precise-security /etc/apt/sources.list > /etc/apt/secsrc.list

• And if you then run the following, you'll see if there are any security updates available (sample output):

  sudo sh -c 'apt-get -o Dir::Etc::sourcelist="secsrc.list" \
  -o Dir::Etc::sourceparts="-" update && \
  apt-get --assume-no upgrade'
  

• This tells apt-get to temporarily use the special security-only sources list, and then runs upgrade, automatically answering no.

• If there are any, run proper apt-get update (which will do a full refresh), and then upgrade.

• You could make the above a bash script with a simple grep/exit code check at the end if you don't feel like parsing the apt-get output :)