systemd: Default to non-stateless images

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

(From OE-Core rev: c5fb399f5894c16cf8eeadd507dc38c29b0fd657)

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/meta/recipes-core/systemd/systemd-systemctl/systemctl b/meta/recipes-core/systemd/systemd-systemctl/systemctl
index d7d4e0d29a..7fdaf8ce03 100755
--- a/meta/recipes-core/systemd/systemd-systemctl/systemctl
+++ b/meta/recipes-core/systemd/systemd-systemctl/systemctl
@@ -241,6 +241,15 @@ 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"