Args passed via `--firstboot-args` are lost if also using `--config-file`

[jlebon]

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

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:

coreos-installer/src/install.rs

Line 40 in 91c9f7f

let config = config.expand_config_files()?;

.

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.

[jlebon]

For anyone hitting this, a workaround is to add a pre-install script which just creates an install config drop-in. E.g. for the ip karg:

#!/bin/bash
set -euo pipefail

# copied from https://github.com/coreos/coreos-installer/blob/91c9f7f4081e19a8f1b5aae6c001fb17ccad6a00/scripts/coreos-installer-service#L21
IFS=" " read -r -a cmdline <<< "$(</proc/cmdline)"
karg() {
    local name="$1" value="${2:-}"
    for arg in "${cmdline[@]}"; do
        if [[ "${arg%%=*}" == "${name}" ]]; then
            value="${arg#*=}"
        fi
    done
    echo "${value}"
}

ip_karg="$(karg ip)"
if [ -n "${ip_karg}" ]; then
    echo "append-karg: [ip=$ip_karg]" > /etc/coreos/installer.d/02-ip-karg.yaml
fi

And then

$ coreos-installer iso customize --pre-install issue-1689-workaround.sh ...

(I'm using the ISO here but the same idea applies to PXE.)

[dustymabe]

Fix proposed in #1699