Ubuntu cloud images have network information “hard coded” in /etc/network/interfaces (ENI). For cloud images, this configuration has always amounted to “dhcp on eth0”. For MAAS images /etc/network/interfaces is a symlink to /run/network/dynamic-interfaces which is populated from within the initramfs by the cloud-initramfs-dyn-netconf package based on the result of ‘ip=’ parameters on the kernel command line. Both of these networking configurations came from the initial use case for the image type. For cloud-images, this was EC2 and for maas-images, the maas ephemeral environment.
The ‘static’ nature of network configuration in these images makes the difficult to use for anything other than their original use case. It also makes specific images required simply for networking configuration.
Items to be fixed with in cloud-init are:
* remove need for xenial images to have persistent networking disabled via kernel command line
* allow easy disabling of cloud-init via kernel command line or file in filesystem
* Defined and sane behavior on re-writing ENI
* Support single and multi-nic network info from by openstack config-drive
* Support dynamic naming of single network device system
* MAAS / iscsi root with ip= but no symlink from ENI to /run/network/dyn-interfaces
* General Cloud-init ‘disable’ kernel command line.
* Cloud-localds support for configuring networking
Many thanks for addressing this. Fixing this for an LTS is much appreciated indeed, as it will make the cloud images much more useful particularly for "real hardware" use cases, and also get rid of some gross hacks in e. g. autopkgtest, and fix the broken ppc64el images along the way (bug 1541757).
Do you have a plan how to test and roll this out? I can help testing this on various architectures and cloud+QEMU, but I think before this lands in the official cloud images this should be tested from a PPA (e. g. by running dist-upgrade on a current cloud image and removing the ifnames=0 hack from the grub config).
FF approved, thanks!