Comment 117 for bug 1357093

The reason why 'apt-get autoremove' is stated there is that it is a simple working way in 16.04 and later for most users, if your system is not broken already. purge-old-kernels is included in some Ubuntu package; consequently it is supported by Launchpad's bug reporting system. But as said in the document, it is currently deprecated and its bugs will likely not be fixed. It might still be useful for some users in some cases.

If one wants to use unattended-upgrades manually, he/she could disable it from being called automatically. One should avoid installing security updates manually by Software Updater in 14.04, if one expects to use apt/unattended-upgrades for removing kernels automatically.

I have developed some software that makes the un-clogging part easier; link to related bountysource.com page is included in the document. Just feel free to post a bounty and/or give some feedback about the interface in the respective Launchpad page. I guess the software could be launched automatically in case of kernel clog when it happens in interactive session (or even in non-interactive session, if the software is made to support completely non-interactive un-clogging).

If you install a kernel manually in command line by say
sudo apt-get install linux-image-4.4.0-87-generic
which kernel(s) that command should remove in turn in your opinion? Or could it be that the user who runs the command should take care of it? User possibly wants to keep some spare kernels, in case the one that is just installed is bad. Or a developer may want to keep some testing kernels etc.