[systemd-devel] Required kernel version for pid1 only?

[Mantas Mikulėnas]

On Tue, Jan 9, 2018 at 10:10 AM, 林自均 <johnlinp at gmail.com> wrote:

> Hi folks,
>
> I saw the following lines in README:
>
> > REQUIREMENTS:
> >         Linux kernel >= 3.13
> >         Linux kernel >= 4.2 for unified cgroup hierarchy support
>
> I guess it means that some part of the whole systemd project requires
> Linux kernel 3.13. What if I don't need that part and only pid1 is relevant
> to me? Is such information provided somewhere?
>

There's no full list. You can only check commit logs to find out why the
requirement was bumped (git log -p README), but once the new dependency is
published, it's always possible that other parts of systemd code will start
implicitly depending on *other* kernel features available in that release.

For example, here's what prompted each bump:

3.13 - DM_DEFERRED_REMOVE (dcce98a4bdc3)
3.12 - %P in core_pattern (58015d7815bc)
3.11 - arbitrary (a0c3e16b7bce)
3.7 - kernel-based firmware loading (be2ea723b1d0)
3.0 - cgroup.procs (e946948eff51)
2.6.39 - oh come on

~

In short, if it says "REQUIREMENTS: Linux ≥ 3.13", that's what you need to
use. Anything below that is at your own risk.

-- 
Mantas Mikulėnas
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