Comment 15 for bug 1899487

Adding some excerpts from cloud-init logs differences between Focal and Bionic, appears to be quite a bit difference in how config is handled.

I also went back and compared if there were other differences like image properties or similar stuff that could find their way into qemu config, but found none.

If you say cloud-init should be equal on Bionic and Focal, where does this information come from apart from the cloud metadata (which also is equal for both instances)?

Focal:
# grep fa:16:3e:d6:d0:91 /var/log/cloud-init.log
2020-10-15 14:48:15,982 - stages.py[DEBUG]: applying net config names for {'version': 1, 'config': [{'type': 'physical', 'mtu': 8942, 'subnets': [{'type': 'dhcp4'}], 'mac_address': 'fa:16:3e:d6:d0:91', 'name': 'ens2'}]}
2020-10-15 14:48:15,991 - __init__.py[DEBUG]: no work necessary for renaming of [['fa:16:3e:d6:d0:91', 'ens2', 'virtio_net', '0x0001']]
2020-10-15 14:48:15,991 - stages.py[INFO]: Applying network configuration from ds bringup=False: {'version': 1, 'config': [{'type': 'physical', 'mtu': 8942, 'subnets': [{'type': 'dhcp4'}], 'mac_address': 'fa:16:3e:d6:d0:91', 'name': 'ens2'}]}
2020-10-15 14:48:18,268 - stages.py[DEBUG]: applying net config names for {'version': 1, 'config': [{'type': 'physical', 'mtu': 8942, 'subnets': [{'type': 'dhcp4'}], 'mac_address': 'fa:16:3e:d6:d0:91', 'name': 'ens2'}]}
2020-10-15 14:48:18,277 - __init__.py[DEBUG]: no work necessary for renaming of [['fa:16:3e:d6:d0:91', 'ens2', 'virtio_net', '0x0001']]

Bionic:
$ grep fa:16:3e:f7:fc:c4 /var/log/cloud-init.log
2020-10-14 19:08:10,670 - stages.py[DEBUG]: applying net config names for {'ethernets': {'ens2': {'dhcp4': True, 'set-name': 'ens2', 'match': {'macaddress': 'fa:16:3e:f7:fc:c4'}}}, 'version': 2}
2020-10-14 19:08:10,679 - __init__.py[DEBUG]: no work necessary for renaming of [['fa:16:3e:f7:fc:c4', 'ens2', 'virtio_net', '0x0001']]
2020-10-14 19:08:10,680 - stages.py[INFO]: Applying network configuration from fallback bringup=False: {'ethernets': {'ens2': {'dhcp4': True, 'set-name': 'ens2', 'match': {'macaddress': 'fa:16:3e:f7:fc:c4'}}}, 'version': 2}
{'type': 'physical', 'name': 'ens2', 'mac_address': 'fa:16:3e:f7:fc:c4', 'match': {'macaddress': 'fa:16:3e:f7:fc:c4'}, 'subnets': [{'type': 'dhcp4'}]}
{'ens2': {'dhcp4': True, 'set-name': 'ens2', 'match': {'macaddress': 'fa:16:3e:f7:fc:c4'}}}
2020-10-14 19:08:12,659 - stages.py[DEBUG]: applying net config names for {'ethernets': {'ens2': {'dhcp4': True, 'set-name': 'ens2', 'match': {'macaddress': 'fa:16:3e:f7:fc:c4'}}}, 'version': 2}
2020-10-14 19:08:12,666 - __init__.py[DEBUG]: no work necessary for renaming of [['fa:16:3e:f7:fc:c4', 'ens2', 'virtio_net', '0x0001']]