WIP: dracut/30ignition: Add mount stage and drop OSTree-specific bits

Add support for the new Ignition `mount` and `umount` stages. The
`mount` stage runs *after* the `disks` stage and
`initrd-root-fs.target`, since we need to be able to mount under
`/sysroot`, but *before* the `files` stage, which will of course drop
files under those mounts.

Combined with coreos/fedora-coreos-config#70,
this allows us to drop all OSTree-specific bits and no longer rely on
`ostree-prepare-root.service` to mount `/var` for us.

dracut/30ignition/ignition-files.service

@@ -5,27 +5,13 @@ Before=ignition-complete.target
 OnFailure=emergency.target
 OnFailureJobMode=isolate
 
-# Ignition files stage starts after /sysroot is mounted.
-Requires=initrd-root-fs.target
-After=initrd-root-fs.target
-
-# Run after ignition-setup has run because ignition-setup
-# may copy in new/different ignition configs for us to consume.
-After=ignition-setup.service
-
-# Make sure root filesystem is mounted read-write
-After=ignition-remount-sysroot.service
+# We need all the filesystems already mounted.
+Requires=ignition-mount.service
+After=ignition-mount.service
 
 # Run before initrd-parse-etc so that we can drop files it then picks up.
 Before=initrd-parse-etc.service
 
-# Network may be required to fetch userdata content.
-After=network.target
-
-# This is guaranteed through After=initrd-root-fs.target but just to
-# be explicit we'll add an After=ignition-disks.service here.
-After=ignition-disks.service
-
 [Service]
 Type=oneshot
 EnvironmentFile=/run/ignition.env

dracut/30ignition/ignition-mount.service

@@ -0,0 +1,23 @@
+[Unit]
+Description=Ignition (mount)
+DefaultDependencies=false
+OnFailure=emergency.target
+OnFailureJobMode=isolate
+
+# Make sure the final /sysroot is ready first, since we're mounting under there
+Requires=initrd-root-fs.target
+After=initrd-root-fs.target
+
+# Make sure root filesystem is remounted read-write if needed
+After=ignition-remount-sysroot.service
+
+# This is guaranteed through After=initrd-root-fs.target but just to
+# be explicit.
+After=ignition-disks.service
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+EnvironmentFile=/run/ignition.env
+ExecStart=/usr/bin/ignition --root=/sysroot --platform=${PLATFORM_ID} --stage=mount --log-to-stdout
+ExecStop=/usr/bin/ignition --root=/sysroot --platform=${PLATFORM_ID} --stage=umount --log-to-stdout

dracut/30ignition/ignition-setup.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
-set -eu
+set -euo pipefail
 
 copy_file_if_exists() {
     src="${1}"; dst="${2}"

dracut/30ignition/module-setup.sh

@@ -49,8 +49,8 @@ install() {
 
     install_ignition_unit ignition-setup.service
     install_ignition_unit ignition-disks.service
+    install_ignition_unit ignition-mount.service
     install_ignition_unit ignition-files.service
-    install_ignition_unit ignition-ask-var-mount.service
     install_ignition_unit ignition-remount-sysroot.service
 }