Bug#1143094: hw-detect: Fails to detect network card under BIOS boot in qemu

Hi Roland,

Thanks for the report.

Roland Clobus <[email protected]> (2026-07-30):
> Hello maintainers of hw-detect,
> 
> The new version of ethdetect.sh does not detect the network interfaces when booting from BIOS.
> 
> This can be seen on openQA [1] where the installer fails to find the network interfaces for the BIOS scenarios. The UEFI scenarios still work.
> 
> From the d-i syslog (broken, BIOS) [2]:
> Jul 29 21:33:12 main-menu[430]: INFO: Menu item 'ethdetect' selected
> Jul 29 21:33:17 net/hw-detect.hotplug: Detected hotpluggable network interface lo
> Jul 29 21:33:18 net/hw-detect.hotplug: Detected hotpluggable network interface ens4
> Jul 29 21:33:18 kernel: [   30.969705] virtio_net virtio0 ens4: renamed from eth0
> Jul 29 21:33:19 check-missing-firmware: looking at dmesg for the first time
> Jul 29 21:33:19 check-missing-firmware: saving timestamp for a later use: [   30.969705]
> Jul 29 21:33:19 check-missing-firmware: no missing firmware in loaded kernel modules
> 
> From the d-i syslog (last working, BIOS) [3]:
> Jul 29 16:03:07 main-menu[430]: INFO: Menu item 'ethdetect' selected
> Jul 29 16:03:13 net/hw-detect.hotplug: Detected hotpluggable network interface lo
> Jul 29 16:03:13 kernel: [   31.465192] virtio_net virtio0 ens4: renamed from eth0
> Jul 29 16:03:13 net/hw-detect.hotplug: Detected hotpluggable network interface ens4
> Jul 29 16:03:14 check-missing-firmware: looking at dmesg for the first time
> Jul 29 16:03:14 check-missing-firmware: saving timestamp for a later use: [   31.465192]
> Jul 29 16:03:14 check-missing-firmware: no missing firmware in loaded kernel modules
> Jul 29 16:03:14 check-missing-firmware: taking network interface ens4 up/down
> Jul 29 16:03:15 check-missing-firmware: looking at dmesg again, restarting from timestamp: [   31.465192]
> Jul 29 16:03:15 check-missing-firmware: timestamp found, truncating dmesg accordingly
> Jul 29 16:03:15 check-missing-firmware: keeping timestamp (no new lines): [   31.465192]
> Jul 29 16:03:15 check-missing-firmware: no missing firmware in loaded kernel modules
> 
> After 1.176 entered unstable, all BIOS installer tests started to fail. There are no version differences in the other udebs, so that's why I report against hw-detect.
> 
> I think it might be caused by the 'Change hw-detect/firmware-lookup
> type to string' change, since that influences whether the network
> interface is taken down and up again.

Commit 619ba547da555a9a87290c8ce9315c3db5376cf0 looks much more plausible
to me, as interface names can be preceeded by a number of spaces, with a
first column that's right-aligned. Depending on if and how the heading is
word-wrapped (I'm seeing Inter-\nface in several cases but I'm not
checking the actual implementation), the number of interfaces, and their
name length, a number of them can go missing. With default QEMU settings
on bookworm, latest mini.iso gets:

    Inter-|
     face |
        lo:
      ens3:

which probably explains the issue down the line.


Cheers,
-- 
Cyril Brulebois ([email protected])            <https://debamax.com/>
D-I release manager -- Release team member -- Freelance Consultant

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