[3343031496] Upstream Reporter: Jonathan Lebon
Upstream issue status: Open
Upstream description:

Normally, parameters specified in a config file (and passed to coreos-installer via `--config-file`) should combine. E.g. with a config file like:

```yaml
append-karg: [foobar]
```

And doing `coreos-installer install --config-file config.yaml --append-karg bazboo`, you'd get both `foobar` and `bazboo` appended.

But `--firstboot-args` is special because it doesn't have any correspondence to a config file entry (and is in fact a hidden option) because it's only meant as an implementation detail of `coreos-installer-service` to help automatically forward certain network-related kargs.

The clobbering happens here: https://github.com/coreos/coreos-installer/blob/91c9f7f4081e19a8f1b5aae6c001fb17ccad6a00/src/install.rs#L40.

A real world scenario of this is basically customizing PXE artifacts once and then booting those customized PXE artifacts on multiple machines where you want different network kargs that you want to specify directly via the PXE config.