dracut: add ignition-kargs stage

Adds a new kargs stage, as well as a binary implementation that prompts
the user to contact their distribution to implement a kargs helper
binary.

dracut/30ignition/ignition-disks.service

@@ -5,7 +5,7 @@ ConditionPathExists=/etc/initrd-release
 DefaultDependencies=false
 Before=ignition-complete.target
 
-# Stage order: setup -> fetch-offline [-> fetch] -> disks -> mount -> files.
+# Stage order: setup -> fetch-offline [-> fetch] [-> kargs] -> disks -> mount -> files.
 After=ignition-fetch.service
 Before=ignition-mount.service
 

dracut/30ignition/ignition-fetch-offline.service

@@ -11,7 +11,7 @@ DefaultDependencies=false
 Before=ignition-complete.target
 After=basic.target
 
-# Stage order: setup -> fetch-offline [-> fetch] -> disks -> mount -> files.
+# Stage order: setup -> fetch-offline [-> fetch] [-> kargs] -> disks -> mount -> files.
 # We run after the setup stage has run because it may copy in new/different
 # ignition configs for us to consume.
 After=ignition-setup-base.service

dracut/30ignition/ignition-fetch.service

@@ -9,7 +9,7 @@ ConditionPathExists=/run/ignition/neednet
 # Don't run if the `fetch-offline` stage successfully fetched a config
 ConditionPathExists=!/run/ignition.json
 
-# Stage order: setup -> fetch-offline [-> fetch] -> disks -> mount -> files.
+# Stage order: setup -> fetch-offline [-> fetch] [-> kargs] -> disks -> mount -> files.
 # We run after the setup stage has run because it may copy in new/different
 # ignition configs for us to consume.
 After=ignition-fetch-offline.service

dracut/30ignition/ignition-files.service

@@ -8,7 +8,7 @@ Before=ignition-complete.target
 OnFailure=emergency.target
 OnFailureJobMode=isolate
 
-# Stage order: setup -> fetch-offline [-> fetch] -> disks -> mount -> files.
+# Stage order: setup -> fetch-offline [-> fetch] [-> kargs] -> disks -> mount -> files.
 After=ignition-mount.service
 
 # Run before initrd-parse-etc so that we can drop files it then picks up.

dracut/30ignition/ignition-kargs-helper.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+set -euxo pipefail
+
+# Send out a warning message to contact the distribution and exit.
+# Distributions implementing Ignition kargs can override this binary
+# with the actual implementation.
+echo "Ignition kernelArguments is not supported by this Linux distribution.\nAsk your distribution to implement ignition-kargs-helper."
+exit 1

dracut/30ignition/ignition-kargs.service

@@ -0,0 +1,22 @@
+[Unit]
+Description=Ignition (kargs)
+Documentation=https://github.com/coreos/ignition
+ConditionPathExists=/etc/initrd-release
+DefaultDependencies=false
+Before=ignition-complete.target
+
+# Stage order: setup -> fetch-offline [-> fetch] [-> kargs] -> disks -> mount -> files.
+After=ignition-fetch.service
+Before=ignition-disks.service
+
+OnFailure=emergency.target
+OnFailureJobMode=isolate
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+EnvironmentFile=/run/ignition.env
+ExecStart=/usr/bin/ignition --root=/sysroot --platform=${PLATFORM_ID} --stage=kargs
+# MountFlags=slave is so the umount of /boot is guaranteed to happen.
+# /boot will only be mounted for the lifetime of the unit.
+MountFlags=slave

dracut/30ignition/ignition-mount.service

@@ -5,7 +5,7 @@ ConditionPathExists=/etc/initrd-release
 DefaultDependencies=false
 Before=ignition-complete.target
 
-# Stage order: setup -> fetch-offline [-> fetch] -> disks -> mount -> files.
+# Stage order: setup -> fetch-offline [-> fetch] [-> kargs] -> disks -> mount -> files.
 # We need to make sure the partitions and filesystems are set up before
 # mounting. This is also guaranteed through After=initrd-root-fs.target but
 # just to be explicit.

dracut/30ignition/ignition-setup-user.service

@@ -8,7 +8,7 @@ Before=ignition-complete.target
 OnFailure=emergency.target
 OnFailureJobMode=isolate
 
-# Stage order: setup -> fetch-offline [-> fetch] -> disks -> mount -> files.
+# Stage order: setup -> fetch-offline [-> fetch] [-> kargs] -> disks -> mount -> files.
 Before=ignition-fetch-offline.service
 
 # We want to make sure we're not racing with multipath taking ownership of the

dracut/30ignition/module-setup.sh

@@ -59,6 +59,9 @@ install() {
     inst_script "$moddir/ignition-setup-user.sh" \
         "/usr/sbin/ignition-setup-user"
 
+    inst_script "$moddir/ignition-kargs-helper.sh" \
+        "/usr/sbin/ignition-kargs-helper"
+
     # Distro packaging is expected to install the ignition binary into the
     # module directory.
     inst_simple "$moddir/ignition" \
@@ -83,6 +86,7 @@ install() {
     install_ignition_unit ignition-setup-user.service
     install_ignition_unit ignition-fetch.service
     install_ignition_unit ignition-fetch-offline.service
+    install_ignition_unit ignition-kargs.service
     install_ignition_unit ignition-disks.service
     install_ignition_unit ignition-mount.service
     install_ignition_unit ignition-files.service