Re: NM in the initrd for Fedora CoreOS

["Colin Walters" <walters verbum org>]

On Sat, Jan 4, 2020, at 10:00 AM, Thomas Haller wrote:
> Hi,
>
>
> On Fri, 2020-01-03 at 14:21 -0500, Colin Walters wrote:
> > I was trying out the current F31 dracut network-manager module, and
> > couldn't get it to do anything useful.
> > See: https://github.com/coreos/fedora-coreos-config/pull/259
>
>
> I don't understand what exactly didn't work (or what you tried).

https://github.com/coreos/fedora-coreos-config/pull/259#issuecomment-570671191

> Is the "network-manager" dracut module loaded? That should be done by
> modules.d/40network/module-setup.sh

Yes.

> I understand this is Fedora 31 CoreOS. But I am not familiar with that,
> which versions of dracut and NetworkManager is that using exactly? Is
> there something special compared to a "regular" Fedora installation?

Part of the idea of all of this is we're not making a separate operating system.  There are details here but 
broadly speaking, same packages from the Fedora repos.

See https://getfedora.org/en/coreos/download/ for main releases, and 
https://builds.coreos.fedoraproject.org/browser for development builds, which can answer that question 
directly, click on "commitmeta.json" e.g. 
https://builds.coreos.fedoraproject.org/prod/streams/testing-devel/builds/31.20191222.20.0/x86_64/commitmeta.json

> > If anyone has a bit of time to help out that'd be appreciated!
> >
> > One higher level architectural question; why is the NM initrd code
> > structured as "run once and quit" rather than running as a systemd
> > unit, same way as the main OS, and default to having the switchroot
> > stop the service?
>
> Good question. I don't know. Lubomir might know.
>
> Maybe: if you run it as systemd service, you would need to know when NM
> is done with configuration. In main OS, that works by NetworkManager-
> wait-online.service. However, that internally uses D-Bus to find out
> when NetworkManager is ready. 

Currently, our main use case for networking in the initrd is Ignition, which just polls in a loop.  
Explicitly watching NM's status for being online would be a potential optimization, but not necessary.

(I think the better way to do this anyways is the code we landed in GLib to monitor netlink for a default 
route)

> But it doesn't seem much of a difference, is it? What would be the
> advantage of running NM as a systemd service? Yes, I don't see why that
> couldn't be done.

There are several advantages, the main reason I'm asking now is avoiding the dracut "initqueue" which is like 
a weird separate init system glued onto the side.  But the general argument here is just having it work the 
same as the main system.