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I need to be able to version control a Ubuntu LTS kernel version at the ABI version level with the matching packages for my current and future installations of a given kernel.

Given the Ubuntu kernel version numbering scheme:

[base kernel version]-[ABI number].[upload number]-[flavour]

Part 1

How long is a given kernel ABI version of the kernel supported for with LTS releases? For example, when creating an Amazon AWS 16.04 image, the kernel is currently 4.4.0-36. In general, how long should I expect the -36 version to remain available? By available I mean I can obtain the image from an official Ubuntu download site and install packages for that OS/kernel version without having to downgrade packages.

Part 2

Assuming I want to be able to support a given ABI level of the Kernel for longer than the ABI version is available on the internet, what do I need to do to mirror the package repositories so I can install packages on my systems? Are there any guides on how to create a local mirror of packages so I can maintain a version controlled OS baseline against a given kernel ABI? I understand that once the kernel has been superseded, it is difficult to take a current image and downgrade it to a desired baseline as the package repository baselines are not archived as such.

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Part 1

How long is a given kernel ABI version of the kernel supported for with LTS releases?

There is no minimum or maximum time - a security update could force an ABI change and since those are unpredictable...

In general, how long should I expect the -36 version to remain available? By available I mean I can obtain the image from an official Ubuntu download site and install packages for that OS/kernel version without having to downgrade packages [emphasis added].

You cannot have any expectation - Ubuntu just doesn't offer you that type of guarantee.

If you CAN accept manual downgrading iIt looks like for Xenial old (security) kernel releases have been kept around for the life of the distro:

linux-image-4.4.0-36-generic_4.4.0-36.55_amd64.deb  2016-08-15 15:44    18M

(from http://security.ubuntu.com/ubuntu/pool/main/l/linux/ ). Eventually Xenial will be EOL and at that point you will have to look to start manually changing apt URLs to go to old-releases.ubuntu.com .

Part 2

Assuming I want to be able to support a given ABI level of the Kernel for longer than the ABI version is available on the internet, what do I need to do to mirror the package repositories so I can install packages on my systems?

I think you'll be OK downgrading at least kernel releases via apt because it doesn't look like the packages themselves are removed but you may end up in an unsupported state (newish userland, old kernel).

  • That is not entirely correct. Installing an older ABI version does not require any downgrading because each ABI version is in a separate package. It is unwise, however, because older ABI versions do not receive bugfixes. – fkraiem Apr 23 at 7:19
  • @fkraiem would you like to edit this answer to be more correct? – Anon Apr 23 at 21:09

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