Bug#809339: systemd: Ignores previously supported & documented method of disabling PredictableNetworkInterfaceNames

[Neil Williams]

On Wed, 30 Dec 2015 13:18:22 -0300
Felipe Sateler <fsateler at debian.org> wrote:

> On Wed, 30 Dec 2015 14:18:35 +0000 Neil Williams
> <codehelp at debian.org> wrote:
> > To get a logfile and to get the boot log, I added options for:
> > --log=809339.log --log-level=debug  --serial-console.
> >
> > There was a temporary issue with the httpredir support, so I added:
> > --mirror=http://mirror.bytemark.co.uk/debian
> >
> > 809339.log is the vmdebootstrap log output.
> > debootstrap.log is the debootstrap output (there were no errors, so
> > this is minimal) boot.log is the qemu boot output (by using the
> > -nographic option when testing the image using qemu).  
> 
> Udev is started in the initramfs. You need to rebuild the initramfs
> after creating the link, the log doesn't show that you did.

Aha, that could do with being in that documentation page.... :-)
 
...

On Thu, 31 Dec 2015 00:36:06 +0100
Michael Biebl <biebl at debian.org> wrote:

> Am 30.12.2015 um 17:18 schrieb Felipe Sateler:
> > Udev is started in the initramfs. You need to rebuild the initramfs
> > after creating the link, the log doesn't show that you did.  
> 
> Fwiw, I just tried to reproduce the issue.
> symlinking 80-net-setup-link.rules to /dev/null still worked to get
> the old wlan0 and eth0 interface names back. But I did indeed have to
> rebuild the initramfs via update-initramfs -u.
> This step is easily forgotten.
> 
> udev's README.Debian only talks about the net.ifnames=0 mechanism.
> Maybe we should extend that section and also add a note about having
> to rebuild the initramfs.

Yes, please. That would fix this bug.

> Well, if someone is defining a bridge, they surely need to somehow add
> the configuration for it to the image. It wouldn't be picked up by
> your auto eth0 rule either. If you spell out in a bit more detail what
> the requirements need to be, then maybe I can suggest a better
> configuration.

This will be part of the documentation for vmdebootstrap and examples
for the customisation scripts, based on examples like this:

http://suihkulokki.blogspot.co.uk/2014/11/using-networkd-for-kvm-tap-networking.html

> Note that systemd-networkd stops processing once it finds a match.
> Thus, adding special config for another interface is as simple as
> adding a file with a more specific match that sorts before 99.

I'll use 99 so that the customise option can be used to create
alternative configurations when building the image (when there is the
option of deleting the pre-existing file anyway).
 
> > Secondly, the systemd-networkd service also needs to be enabled
> > before the interface can be raised during boot (which is what
> > *should* have happened with the vmdebootstrap commands used in the
> > test image above).  
> 
> I don't see anywhere where systemd-networkd is enabled in the
> 809339.log file. networkd is not enabled by default in the systemd
> package, you need to do it manually after install.

Yes, that's a local change I'm looking at in vmdebootstrap. I'm trying
to support a range of options - using eth0 and en* interface names etc.
I'm also trying to see which options can be supported by default and
which need to be done as individual customisations.

-- 


Neil Williams
=============
http://www.linux.codehelp.co.uk/

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