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I have 10 hosts, which are running Ubuntu 20.04.6 LTS. Of these 10, four have a 5.15 kernel, and post a message about "Your Hardware Enablement Stack (HWE) is supported until April 2025." when I log in. The other six have a 5.04 kernel. All have been upgraded regularly using "apt upgrade". At first I thought that the difference might be due to the ability of the underlying BIOS to support GPT vs MBR, but of those capable of supporting GPT, two have the HWE kernel, and three do not. Similarly, of those incapable of supporting GPT, two have the HWE kernel, and three do not.

I have two questions:

  1. what determines whether the HWE upgrade occurs?
  2. is it possible to force the HWE upgrade to occur? If so, how?

Note that the answer at What is hardware enablement (HWE)? provides a lot of information about the HWE variants, and how to add/remove it from what is considered. However, it does not answer my question, which is what caused me to have two flavors of kernel, with no apparent motivation for the difference.

William Atwood
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1 Answers1

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What determines the kernel stack is packages, the packages being installed being set at install time by media used for install, thus you need to consider initial install release for systems, PLUS release & flavor too.

As stated earlier in comments, the install media sets up your defaults, and not just release.

eg.

If an install of Ubuntu 18.04 LTS Desktop is used; there are numerous ISOs provided

  • 18.04 & 18.04.1 Ubuntu Desktop would install the GA kernel stack
  • 18.04.2 thru 18.04.6 LTS Ubuntu Desktop install would install the same 18.04 system only using the HWE kernel stack instead of GA.

This difference is only packages; media used may have been 18.04 for all - but different ISOs with updated packages plus a change of kernel [packages] that occurs at .2 ISO for selected products.

The media used is critical, not just release (18.04 in my example here)

This is covered in https://wiki.ubuntu.com/Kernel/LTSEnablementStack with flavors of Ubuntu still using the defaults of Ubuntu Desktop 18.04, but Ubuntu Desktop 20.04 LTS & later use a different default to 18.04 & earlier, so the release of install needs to be considered.

Note: If you have two 20.04 systems; one installed with Ubuntu 18.04.1 Desktop and the other 20.04.1 Desktop and both have been upgraded & release-upgraded to the point that both are now 22.04.5; those two systems will be using different kernel stacks due to differences in install media (20.04 & 18.04 kernel stacks differ on media; if this example had used Xubuntu 18.04.1 & Xubuntu 20.04.1 media there would be no difference; release AND point release & flavor if involved need to be considered)

FYI: If you didn't keep records of what install media was used; you can details by seeing if metadata still exists, such as

guiverc@d7050-next:~/uwn/issues/877$  cat /var/log/installer/media-info 
Xubuntu 23.10 "Mantic Minotaur" - Daily amd64 (20230829)

On the box I'm using now, I can see my current Lubuntu system was actually installed with a Xubuntu mantic daily using an alpha ISO for a different flavor. As all Desktop flavors use the same defaults, the Xubuntu media will be identical to Lubuntu media if I'd used that; and as the media used was a non-LTS the kernel stack default of this system will be a GA kernel default when I reach a LTS, which will next be 26.04 (I'm currently on plucky of what will be 25.04 on release, so noble or 24.04 was long ago for me now). The install media used is what matters.

guiverc
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