[systemd-devel] Impact when not loading ipv6 and autofs kernel module ...

[Hoyer, Marko (ADITG/SW2)]

> -----Original Message-----
> From: Lennart Poettering [mailto:lennart at poettering.net]
> Sent: Friday, August 09, 2013 5:49 PM
> To: Hoyer, Marko (ADITG/SW2)
> Cc: systemd-devel at lists.freedesktop.org
> Subject: Re: [systemd-devel] Impact when not loading ipv6 and autofs kernel
> module ...
> 
> On Wed, 07.08.13 11:24, Hoyer, Marko (ADITG/SW2) (mhoyer at de.adit-jv.com)
> wrote:
> 
> > Hello systemd developers,
> >
> > I found that systemd automatically tries to load ipv6 and autofs kernel
> modules, when they are not compiled in.
> > Could you give me a hint what is not working, when they are neither provided
> as kernel modules nor compiled in?
> >
> > In case of autofs I found that automount units are not working any more (I
> would have expected this). Without ipv6 I can't find any problems by now.
> >
> > So:
> >
> >
> > 1.       Is there any other impact but the described one when the
> > autofs kernel feature is missing?
> 
> No. .automount units become unavailable, but that's all.
> 
> > 2.       What impact do I have to expect in case the kernel does not provide
> ipv6 functionality?
> 
> Well, support for IPv6 goes away, of course. The reason we explicitly load the
> module at early boot is that we try to configure the loopback device to ::1,
> but that can only work if IPv6 is available in the kernel. Doing this kind of
> loopback configuration of IPv6 however is not hooked up to the kernel-side
> auto-loading of ipv6.ko hence we load it explicitly from usersapce.
> 
> Lennart

Thx for the input.

For what is systemd using the loopback so that it has to set it up so early? Is there any impact when I'm setting up the loopback later. We are probably in a situation where we need ipv4 for general purposes and ipv6 for only special ones. So we'd like to set up ipv6 later for performance reasons, which concerns especially the module loading.

> 
> --
> Lennart Poettering - Red Hat, Inc.


Best regards

Marko Hoyer
Software Group II (ADITG/SW2)

Tel. +49 5121 49 6948