flaf/cloud-init-network-config.md

## cloud-init-network-config.md

      
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              cloud-init-network-config.md
            
          
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It seems that the device ID (id0 in my example) is always used in the rendered configuration, but a udev rule is added to rename this interface to the device ID. The only way where the device ID is not used for me it's when I use set-name: <ifname> to force another name for the interface.
A match: rule with the name property doesn't work for me, in any case, with a fixed name or with globbing in name. The doc says that globbing in name can work only with networkd renderer (ie --output-kind networkd), but for me name has never worked in any case (the device ID is used and no udev rule is present).


Here is my environment:
root@flaf-ubuntu-tmp:~# lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 20.04.3 LTS
Release:	20.04
Codename:	focal

root@flaf-ubuntu-tmp:~# cloud-init --version
/usr/bin/cloud-init 21.3-1-g6803368d-0ubuntu1~20.04.4

root@flaf-ubuntu-tmp:~# ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: ens192: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 00:50:56:a4:a2:c0 brd ff:ff:ff:ff:ff:ff
I use this metadata file to test a basic network configuration:
network:
  version: 2
  ethernets:
    id0: # because `match:` is present, id0 is just an internal ID.
      match:
        name: ens*
      dhcp4: yes
I use match: but this config just says "set ens192 in dhcp configuration".
If I test this metadata for centos/sysconfig or debian/eni, the config is
bad because cloud-init thinks (wrongly) that id0 is the name of an interface:
root@flaf-ubuntu-tmp:~# cat /tmp/network-data.yml 
network:
  version: 2
  ethernets:
    id0:
      match:
        name: ens*
      dhcp4: yes

root@flaf-ubuntu-tmp:~# rm -rf /tmp/network-conf/ && \
    python3 /usr/lib/python3/dist-packages/cloudinit/cmd/devel/net_convert.py \
    --network-data /tmp/network-data.yml --kind yaml --directory /tmp/network-conf/ \
    --distro centos --output-kind sysconfig

Read input format 'yaml' from '/tmp/network-data.yml'.
Wrote output format 'sysconfig' to '/tmp/network-conf/'

root@flaf-ubuntu-tmp:~# LC_ALL=C tree /tmp/network-conf/
/tmp/network-conf/
`-- etc
    |-- sysconfig
    |   |-- network
    |   `-- network-scripts
    |       `-- ifcfg-id0
    `-- udev
        `-- rules.d
            `-- 70-persistent-net.rules

5 directories, 3 files
root@flaf-ubuntu-tmp:~# cat /tmp/network-conf/etc/sysconfig/network-scripts/ifcfg-id0 
# Created by cloud-init on instance boot automatically, do not edit.
#
BOOTPROTO=dhcp
DEVICE=id0
NM_CONTROLLED=no
ONBOOT=yes
TYPE=Ethernet
USERCTL=no


root@flaf-ubuntu-tmp:~# rm -rf /tmp/network-conf/ && \
    python3 /usr/lib/python3/dist-packages/cloudinit/cmd/devel/net_convert.py
    --network-data /tmp/network-data.yml --kind yaml --directory /tmp/network-conf/ \
    --distro debian --output-kind eni

Read input format 'yaml' from '/tmp/network-data.yml'.
Wrote output format 'eni' to '/tmp/network-conf/'

root@flaf-ubuntu-tmp:~# LC_ALL=C tree /tmp/network-conf/
/tmp/network-conf/
`-- etc
    |-- network
    |   `-- interfaces.d
    |       `-- 50-cloud-init
    `-- udev
        `-- rules.d
            `-- 70-persistent-net.rules

5 directories, 2 files
root@flaf-ubuntu-tmp:~# cat /tmp/network-conf/etc/network/interfaces.d/50-cloud-init 
# 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}
auto lo
iface lo inet loopback

auto id0
iface id0 inet dhcp
Have I missed something or is it a bug of cloud-init concerning the support of the "networking config version 2" support?
I have just tried to follow this doc.
Thanks for you help.