What is the definition of a "standard security update"? What other classifications are possible?

Since recently upgrading to 20.04 I see informational messages after running apt update similar to

46 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
31 standard security updates

Googling has failed to turn up the definition of the phrase standard security update. What is it? And, are there non-standard security updates? What possibilities are there?

Solution 1:

Seems to a part of ubuntu-advantage-tools to distinguish between freely available security updates (standard) and ESM (paid, later, actual for 16.04 LTS).

May be removed by removing special UA hook by

sudo rm /etc/apt/apt.conf.d/20apt-esm-hook.conf

Above will transform

42 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
29 standard security updates

to normal traditional behaviour

42 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.

All this UA ESM stuff on supported Ubuntu versions smells like big BUY word with capital letters.
I found this unacceptable. Especially the viral behavior of UA:

$ sudo apt autopurge ubuntu-advantage-tools
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be REMOVED:
 distro-info* python3-debconf* ubuntu-advantage-tools* ubuntu-mate-core* ubuntu-mate-desktop* ubuntu-minimal* ubuntu-release-upgrader-core*
 ubuntu-release-upgrader-gtk* update-manager* update-manager-core* update-notifier* update-notifier-common*
0 upgraded, 0 newly installed, 12 to remove and 41 not upgraded.
After this operation, 6 687 kB disk space will be freed.
Do you want to continue? [Y/n] n
Abort.

I have reported a bug 1950692 about ubuntu-advantage-tools "integration".

Clues:

• http://changelogs.ubuntu.com/changelogs/pool/main/u/update-notifier/update-notifier_3.192.30.9/changelog :

  update-notifier (3.192.30.7) focal; urgency=medium

  • data/apt_check.py:
    ...
    • Make distinction between standard security updates and ESM updates when performing package counts. (LP: #1926208)

• https://git.launchpad.net/update-notifier/tree/data/apt_check.py#n254

• https://github.com/canonical/ubuntu-advantage-client/blob/0e971e09ca30f21d581c0e8273579e892d198920/features/attach_validtoken.feature#L95

Solution 2:

You're right about standard security updates. Those are delivered in the Ubuntu Main respository for the initial 5 years of any Ubuntu LTS release. For example, Ubuntu 20.04 LTS benefits from it until 2025.

The ESM security updates are indeed in a different category - they go beyond standard security updates. The access requires a subscription, but it doesn't necessarily mean that you will have to pay anything. Anyone can get a free subscription for personal use.

To subscribe: https://ubuntu.com/advantage To learn more: https://www.omgubuntu.co.uk/2021/09/ubuntu-16-04-security-updates-esm-for-free

Full disclosure, I am a product manager at Canonical.