Cloud Init not reading drop-ins sections since Flatcar 3975.2.0.

[snikhil1998]

Description

CoreOS Cloud Init is not reading the drop-ins sections in cloud-config.yml since Flatcar 3975.2.0.

Impact

Some fixes implemented by us are not being read from cloud-config.yml.

Environment and steps to reproduce

1. Set-up: VMware ESXi
2. Task: Freshly deploying the OVA, modifications for drop-ins sections in cloud-config.yml

Expected behavior

The drop-ins sections should be read and the drop-in files should be created/modified accordingly.

[jepio]

This is called out in the release notes for 3975.2.0:
"Removed coreos-cloudinit support for automatic keys conversion (e.g reboot-strategy -> reboot_strategy) (scripts#1687)"

We needed to remove this to upgrade the yaml library used in cloudinit, the previously used one was unmaintained and had vulnerabilities.

Changing it to drop_ins should work.

[snikhil1998]

Does changing drop-ins to drop_ins work on Flatcar Linux 3815.2.x and older?

[jepio]

Yes, the canonical name of that section was always drop_ins but the old yaml parser performed automatic conversion for drop-ins. This isn't supported in newer parser versions. It's also unfortunate that the examples in docs used drop-ins.