Bug#842201: hw-detect: Spurious "No network interfaces detected" under QEMU

[Julien Muchembled <jm@jmuchemb.eu>]

Package: hw-detect
Version: 1.108
Severity: normal
Tags: d-i

Using preseeding, I came into the problem that the installer occasionally fails
because it could not detect the network interface. There really is one, and if
I connect to the guest with VNC, I can go back, retry and it works.

Maybe things are going too fast at some point in a fully automated install.
I started to debug and I found that the issue is probably in the
/bin/hw-detect script, when it is called by /bin/ethdetect

I use the following command line to debug:

  $ qemu-system-x86_64 -k fr -enable-kvm -smp 1 -m 256 -net nic -net user,hostfwd=tcp:127.0.0.1:2222-:22 -cdrom debian-8.6.0-amd64-netinst.iso -kernel vmlinuz -initrd initrd.gz -vnc 127.0.0.1:1 -append 'priority=critical language=C country=FR keymap=fr(latin9) anna/choose_modules=network-console,openssh-client-udeb network-console/password=root network-console/password-again=root'

where vmlinuz & initrd.gz are extracted from the iso (from install.amd folder).

In order to easily reproduce the issue, I added the following line to the
/etc/inittab file in the initrd:

  tty5::once:tail -f -n 0 /var/log/syslog |(grep -m1 'rdnssd started'; reboot)

Now, the really strange thing is that the issue disappears if I add

  fb=false

to the kernel command line. At least, I have a workaround, but for how long?


Tested with qemu-system-x86 1:2.7+dfsg-1 on amd64.
Using '-net nic,model=virtio' does not change anything.