Bug#1105204: udev: networking broken by interface name change upgrading from bookworm to trixie enp1s0 -> ens1

[Luca Boccassi]

Control: forcemerge 1105204 1105223
Control: tags 1105204 wontfix
Control: close 1105204

On Tue, 13 May 2025 12:31:41 +0200 Emanuele Rocca <ema at debian.org>
wrote:
> Package: udev
> Version: 257.5-2
> Severity: important
> 
> Hi!
> 
> We tested a bookworm to trixie update on one of our systems. The host
> did not come back online after reboot, and the issue seems to be
caused
> by the 252 -> 257 systemd update.
> 
> The main network interface on the system was named "enp1s0" by
systemd
> 252.36 shipped with bookworm. After upgrading the machine to trixie
and
> rebooting, the host was unreachable via the network. Logging in via
> out-of-bound console it became evident that systemd v257 on trixie
chose
> a different name for the network interface: "ens1".
> 
> After rebooting the machine passing net.naming_scheme=v252 to the
kernel
> command line, we verified that the interface name went back to
"enp1s0".

This is expected due to kernel changes. Names can always change if the
kernel changes its internal behaviour, you have to fix them if you
don't want that to happen. This is documented at:

https://www.freedesktop.org/software/systemd/man/latest/systemd.net-naming-scheme.html