[OE-core] [OE-Core][PATCH] systemd: Default to non-stateless images

[Alex Kiernan]

When creating images, for anything other than the explicitly stateless
case, touch /etc/machine-id so that the images can be booted without an
initramfs and with `ro` set on the kernel command line, otherwise system
refuses to start:

  [    7.222134] systemd[1]: No hostname configured.
  [    7.227266] systemd[1]: Set hostname to <localhost>.
  [    7.232622] systemd[1]: System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.
  [    7.241750] systemd[1]: Booting up is supported only when:
  [    7.247362] systemd[1]: 1) /etc/machine-id exists and is populated.
  [    7.253752] systemd[1]: 2) /etc/machine-id exists and is empty.
  [    7.259757] systemd[1]: 3) /etc/machine-id is missing and /etc is writable.

If DISTRO_FEATURES includes `stateless` then systemctl-native is not run
on the image leaving the image for population at runtime by systemd.

Signed-off-by: Alex Kiernan <alex.kiernan at gmail.com>
---

 meta/classes/image.bbclass                            | 7 +++----
 meta/recipes-core/systemd/systemd-systemctl/systemctl | 8 ++++++++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
index a23403c0827a..3cb185dd2045 100644
--- a/meta/classes/image.bbclass
+++ b/meta/classes/image.bbclass
@@ -665,12 +665,11 @@ reproducible_final_image_task () {
     fi
 }
 
-IMAGE_EXTRADEPENDS += "${@bb.utils.contains('DISTRO_FEATURES', 'systemd', 'systemd-systemctl-native', '', d)}"
-
 systemd_preset_all () {
-	systemctl --root="${IMAGE_ROOTFS}" --preset-mode=enable-only preset-all
+    systemctl --root="${IMAGE_ROOTFS}" --preset-mode=enable-only preset-all
 }
 
-IMAGE_PREPROCESS_COMMAND_append = " ${@bb.utils.contains('DISTRO_FEATURES', 'systemd', 'systemd_preset_all;', '', d)} reproducible_final_image_task; "
+IMAGE_EXTRADEPENDS += "${@ 'systemd-systemctl-native' if bb.utils.contains('DISTRO_FEATURES', 'systemd', True, False, d) and not bb.utils.contains('DISTRO_FEATURES', 'stateless', True, False, d) else ''}"
+IMAGE_PREPROCESS_COMMAND_append = " ${@ 'systemd_preset_all;' if bb.utils.contains('DISTRO_FEATURES', 'systemd', True, False, d) and not bb.utils.contains('DISTRO_FEATURES', 'stateless', True, False, d) else ''} reproducible_final_image_task; "
 
 CVE_PRODUCT = ""
diff --git a/meta/recipes-core/systemd/systemd-systemctl/systemctl b/meta/recipes-core/systemd/systemd-systemctl/systemctl
index d7d4e0d29a09..7da8f23ab893 100755
--- a/meta/recipes-core/systemd/systemd-systemctl/systemctl
+++ b/meta/recipes-core/systemd/systemd-systemctl/systemctl
@@ -241,6 +241,14 @@ def preset_all(root):
         if state == "enable" or state is None:
             enable(root, service, location, services)
 
+    # If we populate the systemd links we also create /etc/machine-id, which
+    # allows systemd to boot with the filesystem read-only before generating
+    # a real value and then committing it back.
+    #
+    # For the stateless configuration, where /etc is generated at runtime
+    # (for example on a tmpfs), this script shouldn't run at all and we
+    # allow systemd to completely populate /etc.
+    (root / SYSCONFDIR / "machine-id").touch()
 
 def mask(root, *services):
     systemdir = root / SYSCONFDIR / "systemd" / "system"
-- 
2.17.1