constant kernel version in xenial

[Andy Whitcroft]

On Tue, Jun 28, 2016 at 09:26:47AM +0000, Raiman, Timor wrote:

> We need to configure a pool of machines to use the exact same kernel
> version.  We found that some kernels appear in the Ubuntu repositories
> and then are removed when a newer package is available (eg, 4.4.0.24.25
> is not available since 4.4.0.28.30 was uploaded).

> Can we rely on certain kernel versions to remain available in the
> repositories for a significant length of time?
> For example, I see that 4.4.0.21.22 has been available for a while
> (18 Apr 2016)

The package versions above are for the linux-meta package.  The purpose
of this package is to always point to the latest released kernel and as
such will always move forward as we release Stable Release Update (SRU)
to the kernel.  These typically occur every three weeks in step with the
SRU release cadance.

The Ubuntu respositories (the archive pool) only holds kernels which
are currently published in an archive pocket (you will see discussion
of Xenial Release, Security, Updates and Proposed).  Essentially these
are the current supported kernel and any pending kernels which are in
testing for release.  There is an anomoly with the version which was in
the Release pocket when 16.04 LTS was released.  That pocket is frozen at
the time of the release and therefore the version in that pocket is also
available in the archive pool indefinately (4.4.0.21.22 in 16.04 LTS);
rapidly becoming stale.  All other kernels are transitory as they are
replaced by later updates.

>From an apt-get perspective we only expect to see the most recent stable
kernel as avialable for install.  That said the launchpad librarian
always maintains a copy of every kernel produced.  Pointers to these can
be found on the publishing history page for the linux package:

	https://launchpad.net/ubuntu/+source/linux/+publishinghistory

Where people wish to have greater control over versions and the application
of updates for local systems it is normal to maintain a separate local
archive from which those systems update and to which updates are applied
as and when is appropriate by local policy.  This is typically done as
a selective mirror of the Ubuntu archive.  Another option would be to
use a launchpad PPA with the appropriate versions copied over from the
main archive.

Hope this makes sense.

-apw