cloud-init should support setting apply_network_config through Azure instance metadata

This bug was originally filed in Launchpad as [LP: #1889112](https://bugs.launchpad.net/cloud-init/+bug/1889112)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2020-07-27T17:49:49.392976+00:00

date_fix_committed = None

date_fix_released = None

id = 1889112

importance = undecided

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1889112

milestone = None

owner = johnsonshi

owner_name = Johnson Shi

private = False

status = triaged

submitter = johnsonshi

submitter_name = Johnson Shi

tags = []

duplicates = []

_Launchpad user **Johnson Shi(johnsonshi)** wrote on 2020-07-27T17:49:49.392976+00:00_

cloud-init currently only supports reading and setting the Azure apply_network_config option from disk (see https://cloudinit.readthedocs.io/en/latest/topics/datasources/azure.html#configuration).

This means that for customers using images that have "Azure apply_network_config" set to true on disk, there is no way for customers to opt out of this behavior during VM deployment. This is because the sole location that cloud-init reads for the "Azure apply_network_config" option is from the disk.

For customers that want to opt out of this behavior, the mitigation for customers would be to (1) deploy the VM, (2) ssh into the VM, (3) set the "Azure apply_network_config" option to false on disk, (4) then reboot the VM in order for the changes to take effect and prevent cloud-init from applying network config on subsequent boots.

Since there is no way to opt out of this behavior on first boot, a good feature request would be for cloud-init to support reading the "Azure apply_network_config" option through cloud-configs passed in through Azure instance metadata.