cloud-init isn't the source of this configuration, so I'm marking our
task Incomplete and adding subiquity (which I believe generates this
config).
(Regardless, I've responded to a couple of things below for background.)
> I think with the right tooling (ip, ifconfig, ethtool or even the
network-manager UI) you can even change MAC addresses today on other
platforms.
There's a substantial difference between people being able to opt into
changing MACs and the platform not providing stable MACs. In the former
case, we can tell people to stop doing it, or tell them other manual
steps that they can perform when they are manually changing their MAC.
In the latter case, we don't have that option. ;)
> Nowadays interface names are based on their underlying physical
device/address (here in this case '600' or to be precise '0600' -
leading '0' are removed), which makes the interface and it's name
already quite unique - since it is not possible to have two devices (in
one system) with the exact same address.
This may be true for Z, but it isn't for cloud instances because the
"physical" device can move between PCI ports on reboot, for example, or
be named differently based on the order in which the kernel detects each
interface. In these cases, using the MAC address is a lot more reliable
than using the physical address.
** Changed in: cloud-init
Status: New => Incomplete
** Also affects: subiquity
Importance: Undecided
Status: New
** Summary changed:
- Cloud-init uses macaddress keyword on s390x where MAC addresses are not
necessarily stable/unique across reboots
+ When installing with subiquity, the generated network config uses the
macaddress keyword on s390x (where MAC addresses are not necessarily stable
across reboots)
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https://bugs.launchpad.net/bugs/1869155
Title:
When installing with subiquity, the generated network config uses the
macaddress keyword on s390x (where MAC addresses are not necessarily
stable across reboots)
Status in cloud-init:
Incomplete
Status in subiquity:
New
Status in Ubuntu on IBM z Systems:
New
Bug description:
While performing a subiquity focal installation on an s390x LPAR (where the
LPAR is connected to a VLAN trunk) I saw a section like this:
match:
macaddress: 02:28:0b:00:00:53
So the macaddress keyword is used, but on several s390x machine generation
MAC addresses are
not necessarily stable and uniquie across reboots.
(z14 GA2 and newer system have in between a modified firmware that ensures
that MAC addresses are stable and uniquire across reboots, but for z14 GA 1 and
older systems, incl. the z13 that I used this is not the case - and a backport
of the firmware modification is very unlikely)
The configuration that I found is this:
$ cat /etc/netplan/50-cloud-init.yaml
# This file is generated from information provided by the datasource. Changes
# to it will not persist across an instance reboot. To disable cloud-init's
# network configuration capabilities, write a file
# /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
# network: {config: disabled}
network:
ethernets:
enc600:
addresses:
- 10.245.236.26/24
gateway4: 10.245.236.1
match:
macaddress: 02:28:0b:00:00:53
nameservers:
addresses:
- 10.245.236.1
set-name: enc600
version: 2
(This is a spin-off of ticket LP 1868246.)
It's understood that the initial idea for the MAC addresses was to have a
unique identifier, but
I think with the right tooling (ip, ifconfig, ethtool or even the
network-manager UI) you can even change MAC addresses today on other platforms.
Nowadays interface names are based on their underlying physical
device/address (here in this case '600' or to be precise '0600' -
leading '0' are removed), which makes the interface and it's name
already quite unique - since it is not possible to have two devices
(in one system) with the exact same address.
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