Move to conditional networking

We have all the piece in place now to move to conditional networking. So
let's drop the firstboot kargs, as well as
coreos-liveiso-network-kargs.service, which is no longer needed (i.e.
the live ISO will now enable initrd networking as required given the
embedded Ignition config).

Fixes: coreos/fedora-coreos-tracker#443

image.yaml

@@ -9,10 +9,9 @@ extra-kargs:
     # https://fedoraproject.org/wiki/Changes/CGroupsV2
     - systemd.unified_cgroup_hierarchy=0
 
-# Kernel arguments to be used on first-boot.
-ignition-network-kcmdline:
-    - 'rd.neednet=1'
-    - 'ip=dhcp,dhcp6'
+# Disable networking by default on firstboot. We can drop this once cosa stops
+# defaulting to `ip=dhcp,dhcp6 rd.neednet=1` when it doesn't see this key.
+ignition-network-kcmdline: []
 
 # Optional remote by which to prefix the deployed OSTree ref
 ostree-remote: fedora

overlay.d/05core/usr/lib/dracut/modules.d/20live/live-generator

@@ -31,7 +31,6 @@ add_requires sysroot.mount     initrd-root-fs.target
 add_requires sysroot-etc.mount initrd-root-fs.target
 add_requires sysroot-var.mount initrd-root-fs.target
 
-add_requires coreos-liveiso-network-kargs.service              initrd.target
 add_requires coreos-liveiso-reconfigure-nm-wait-online.service initrd.target
 
 mkdir -p "${UNIT_DIR}/ostree-prepare-root.service.d"

overlay.d/05core/usr/lib/dracut/modules.d/20live/module-setup.sh

@@ -34,12 +34,6 @@ install() {
     inst_simple "$moddir/writable.mount" \
         "$systemdsystemunitdir/writable.mount"
 
-    inst_simple "$moddir/coreos-liveiso-network-kargs.sh" \
-        "/usr/sbin/coreos-liveiso-network-kargs"
-
-    inst_simple "$moddir/coreos-liveiso-network-kargs.service" \
-        "$systemdsystemunitdir/coreos-liveiso-network-kargs.service"
-
     inst_simple "$moddir/coreos-liveiso-reconfigure-nm-wait-online.service" \
         "$systemdsystemunitdir/coreos-liveiso-reconfigure-nm-wait-online.service"
 }

overlay.d/05core/usr/lib/systemd/system/coreos-liveiso-success.service

@@ -4,8 +4,7 @@
 [Unit]
 Description=CoreOS Live ISO virtio success
 Documentation=https://github.com/coreos/fedora-coreos-config
-# Only run on the Live ISO, and only if there's no Ignition config;
-# the second bits here invert the conditionals in coreos-liveiso-network-kargs.service.
+# Only run on the Live ISO, and only if there's no Ignition config
 ConditionKernelCommandLine=coreos.liveiso
 ConditionPathExists=!/config.ign
 ConditionVirtualization=|kvm