Re: [gentoo-user] Why I can't I build systemd without ipv6?

[Rich Freeman <rich0@gentoo.org>]

On Fri, Oct 13, 2017 at 11:34 AM, Mike Gilbert <floppym@gentoo.org> wrote:
> On Fri, Oct 13, 2017 at 1:29 PM, Daniel Frey <djqfrey@gmail.com> wrote:
>>
>> So *why* on earth is it a dependency when (from what I've been reading after
>> discovering this) many ISPs don't seem to support it properly yet?
>>
>> And is there a way to build systemd without ipv6? Or am I going to have to
>> revert these three systems back to openrc?
>
> Instead of stripping IPv6 out of your kernel, I would suggest that you
> simply disable it on any network interfaces. How you do this would
> depend on the method you use to manager your network config.
>
> If you really want to remove IPv6 from your kernel, simply disable the
> GENTOO_LINUX_INIT_SYSTEMD config option, and enable the other other
> dependencies manually.
>
> https://gitweb.gentoo.org/proj/linux-patches.git/tree/4567_distro-Gentoo-Kconfig.patch#n106
>

Just to expand a bit on this - the Gentoo-added service manager kernel
options are purely for convenience.  If you don't use gentoo-sources
you won't see them at all, because they're not part of the upstream
kernel.  All they do is pull in a bunch of other options.  Back in the
"good old days" people would look at the wiki (or pre-wiki) page for
openrc, see a list of mandatory kernel options, and set those options
when building their kernel.  Then somebody had the clever idea that it
would be easier for users to not shoot themselves in the foot if we
just gave a one-click option that set all the requirements
automatically.  However, the kernel configuration settings doesn't
really have any concept of "optional dependencies" - so we're stuck
with either not pulling in ipv6, which mostly works, or pulling it in,
which always works.

It is completely safe to answer no to whether you use systemd and
openrc, and then just manually answer yes to the things that you need.
Just keep in mind that you may run into issues if you don't enable
something that is truly mandatory, or you might have diminished
functionality.  It also means that you need to keep your ears open for
when the requirements change, since there won't be a Gentoo automagic
kernel config setting to change things for you.  That said, running an
upstream kernel isn't really that big a deal - I do that since I run
btrfs and zfs and want to have a bit more control over which series
I'm running to mitigate the bugs.

-- 
Rich