Hello,
When doing a “sudo apt full-upgrade” I get “The following packages have been kept back”.
When doing an update with Discover, it says it’s already updated. So no updates available.
When doing " sudo pkcon refresh && sudo pkcon update", it lists the same packages that “apt full-upgrade” listed, but in its case it offers to update them ( Proceed with changes? [N/y] ).
So what is one to do?
Answer “yes” to the pkcon prompt? What could be the consequences of yes vs no?
Thanks for any help.
This is what Canonical are calling Phased Updates.
The idea is that some updates may be considered less urgent, or more risky, so you don’t issue an update immediately to everyone - you specify that an update will first go out to 10% of the users, after a week it will go out to another 20% of the users and after another week - to all users. That way if an update is found to be problematic, the distributor can issue a fix before the problem hits all users.
The way it works (and there are a lot more details in the above linked document) is that your computer has a pseudo-random “machine ID” that is generated locally when you install the operating system for the first time and is never changed (you can see it in the file /etc/machine-id), and when a phased update is starting, it is also assigned a random seed. When your local apt looks at a phased update it can calculate “how far” your machine id is from the phased update seed and then look at the phased release plan and determine in which batch your machine is and whether it should take the update now or wait.
The pkcon tool that is part of the PackageKit software manager abstraction kit does not support phased updates and will therefor just ignore a phased release plan.
In regards to what you should do - the documentation link explains why phased updates are a good idea. If you buy into that (I did) then don’t worry - you will get those updates eventually. If you don’t buy into the reasoning - the document above has instructions on how you can set your apt to “opt out” of phased updates, or you can just use pkcon - it is up to you to decide 
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Wow. Thank you very much guss77.