LTS - What it and and what it is not

Richard Purdie

I (and the YP TSC) are seeing various interesting things happening with
the LTS. I think in general its good for the project, it is helping
users and it is being positively received. We are starting to see
various "pressures" on how it is being used as master and dunfell
diverge naturally over time and I want to spell these issues out for
people so that can try and avoid being drawn into traps.

Most of the issues are around the fact that our LTS now does not have
the latest components in it. In particular, it doesn't have the latest
toolchain (gcc 10 isn't there), the latest kernel (no 5.10) or the
latest graphics stack (no new wayland features).

From an engineering perspective, most things are ultimately possible
with a build system but that doesn't however mean they're a good idea.
In isolation, it is possible to change+fix some of these things but
usually only for some smaller subset of the ecosystem. Its unlikely
that gcc 10 patches are going to be accepted in all dunfell layers for
example (and quite rightly too). What that means is that you then
fragment the ecosystem into your island where it works and the rest of
it where it stands a good chance it will not.

In some cases this may be fine but people do need to be extremely aware
that once on your own island, you lose the benefit of co-
travellers/compatibility and you have to do your own testing and

I think that people need to think long and hard about whether they are
maintaining an existing release of something, or actively developing
something which isn't yet in a stable lifecycle and therefore may not
be a good fit for the LTS.

In many cases older releases of a BSP, or a software stack can "fall"
off onto the LTS, but the LTS isn't a way to allow current development
of the latest and greatest without interruption of upstream changes.
This means that LTS isn't a way to stop testing/developing against

We probably do need to develop some documentation about what the LTS
is/isn't and how best to use it, so any help with doing that would be
much appreciated. Please do help us try and educate people that whilst
the LTS is a good thing, it doesn't solve every problem and how to spot
the signs where it may not be the right solution!



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