Bug#881771: release-notes: No mention of "predictable network interface names" in Debian 10
Andrei POPESCU wrote:
>> In issues.dbk:
>>
>> <section id="migrate-interface-names">
>> <title>Migrating from legacy network interface names</title>
>> <para>
>> If your system was upgraded from an earlier release, and still uses
>> the old-style network interface names that were deprecated with
>> stretch (such as <literal>eth0</literal> or <literal>wlan</literal>),
>
> s/eth0/eth/ ? (since you used the non-numbered names also in upgrading.dbk)
Here I'm just giving a familiar example to identify the scheme from.
(Oh, you're right, I'm inconsistent.)
>> you should be aware that <systemitem role="package">udev</systemitem>
>> in buster no longer supports the mechanism of defining their names via
>> <filename>/etc/udev/rules.d/70-persistent-net.rules</filename>. To
>> avoid the danger of your machine losing networking after the upgrade
>> to buster, it is recommended that you migrate in advance to the new
>> naming scheme (usually meaning names like <literal>enp0s1</literal> or
>> <literal>wlp2s5</literal>, which incorporate PCI bus- and
>> slot-numbers). Take care to update any interface names hard-coded in
>> configuration for firewalls, <systemitem role="package">ifupdown</systemitem>.
>> and so on.
>> </para>
>> <para>
>> The alternative is to switch to a supported mechanism for enforcing
>> the old naming scheme, such as the <literal>net.ifname=0</literal>
>> kernel commandline option or a systemd <filename>.link</filename>
>> file.
>
> Point to systemd.link(5)?
Oh yes, I forgot to come back to this. It's not completely clear what
the approved method of doing manpage links is, but one option is to
point at
<ulink url="https://manpages.debian.org/stretch/udev/systemd.link.5.html";>systemd.link(5)</ulink>.
or maybe just
<ulink url="https://manpages.debian.org/systemd.link";>systemd.link(5)</ulink>.
>> </para>
>> <para>
>> To find the new-style names that will be used, first find the
>> current names of the relevant interfaces:
>> </para>
>> <screen
>> $ echo /sys/class/net/[ew]*
>> </screen>
>> <para>
>> For each one, check whether it is used in configuration files:
>> </para>
>> <screen>
>> $ sudo rgrep -w eth0 /etc
>> </screen>
>> <para>
>> And what name <systemitem role="package">udev</systemitem> would prefer to
>> use for it:
>> </para>
>> <screen>
>> $ udevadm test-builtin net_id /sys/class/net/eth0 2>/dev/null
>> </screen>
>> <para>
>> (One of these may be a fallback MAC-based name, sometimes needed
>> for USB network hardware.)
>> </para>
>>
>> [Possibly add extra details there for other special cases]
(In particular there are onboard cards and PCI hotplug cards, but the
upstream docs explain these better than I could.)
>>
>> <para>
>> To switch over, disable <filename>70-persistent-net.rules</filename>
>> either by renaming it or by commenting out individual lines.
>> On virtual machines you will need to remove the files
>> <filename>/etc/systemd/network/99-default.link</filename> and
>> (if using virtio network devices)
>> <filename>/etc/systemd/network/50-virtio-kernel-names.link</filename>.
>> Then rebuild the <filename>initrd</filename>:
>> </para>
>> <screen>
>> $ sudo update-initramfs -u
>> </screen>
>> <para>
>> and reboot. Your system should now have new-style network interface
>> names. Adjust any remaining configuration files, and test your system.
>> </para>
>
> https://wiki.debian.org/NetworkConfiguration#Predictable_Network_Interface_Names
> suggests this might not be sufficient to activate the predictable naming
> on stretch, is this tested?
It was enough for me, but there are also at least two other ways of
complicating matters:
* a net.ifnames=0 option in your grub config
* masking /dev/null symlinks in /etc/systemd/network/
Setting up one of those then forgetting about it might cause problems.
>> [possibly a paragraph about safe upgrades over SSH]
>
> I believe your text above provides sufficient information to enable a
> remote sysadmin to deal with this without further help.
Given unlimited space and copious reliable sources we could also
produce a decision tree for which configuration files to modify before
or after the reboot, and whether to do test-runs with one-off kernel
options and dead-man's-handle cronjobs, and so on, but a small and
inaccurate version would probably do more harm than good.
>
>> <para>
>> See the
>> <ulink url="https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/";>upstream
>> documentation</link> and the <literal>udev</literal>
>> <filename>README.Debian</file> for further information.
>> </para>
>> </section>
>>
>> And/or maybe a pointer to some useful page in the Debian Wiki, but I
>> suspect we'd need to write one first.
>>
>> Then in upgrading.dbk
>>
>> <section id="review-interface-names">
>> <title>Verify network interface name support</title>
>> <para>
>> Systems upgraded from older releases that still use network interfaces
>> with names like <literal>eth</literal> or <literal>wlan</literal> are
>> at risk of losing networking once they switch to buster; see
>> <xref linkend="migrate-interface-names"/> for migration instructions.
>> </para>
>> </section>
Oh, you're right; there's no reason for that to say "eth" that
wouldn't also apply in the previous one. This should either say "like
eth0 or wlan0" or "with names starting with eth- or wlan-".
--
JBR with qualifications in linguistics, experience as a Debian
sysadmin, and probably no clue about this particular package
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