[PATCH v2] classes/image-postproc-extension: Remove /etc/machine-id

[Quirin Gylstorff <Quirin.Gylstorff@siemens.com>]

From: kas <kas@example.com>

In a read-only system the machine id should be deleted or
set to `unitialized\n`[1]. 

Systemd will generate a new machine-id during the first boot.
In the case of a read-only root file system Systemd generates a mount point with
the machine id. If an overlay for /etc is used this creates a mount conflict.
To avoid the conflict between the overlay filesystem and systemd /etc/machine-id
mount point deleted the file /etc/machine-id.


This partly reverts 98d6a72d3064. The man page[2] was updated for Debian Bullseye to
allow a missing machine id. For Debian Bullseye it reads:

```
For operating system images which are created once and used on multiple machines,
for example for containers or in the cloud, /etc/machine-id should be either missing
or an empty file in the generic file system image
```

[1]: https://systemd.io/BUILDING_IMAGES/
[2]: https://manpages.debian.org/bullseye/systemd/machine-id.5.en.html

Signed-off-by: Quirin Gylstorff <quirin.gylstorff@siemens.com>
---

Changes V2:
 - add information about revert of 98d6a72d3064

 meta/classes/image-postproc-extension.bbclass | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/meta/classes/image-postproc-extension.bbclass b/meta/classes/image-postproc-extension.bbclass
index ca520273..0c412c0d 100644
--- a/meta/classes/image-postproc-extension.bbclass
+++ b/meta/classes/image-postproc-extension.bbclass
@@ -57,7 +57,7 @@ ROOTFS_POSTPROCESS_COMMAND =+ "image_postprocess_machine_id"
 image_postprocess_machine_id() {
     # systemd(1) takes care of recreating the machine-id on first boot
     sudo rm -f '${IMAGE_ROOTFS}/var/lib/dbus/machine-id'
-    sudo install -m 644 '/dev/null' '${IMAGE_ROOTFS}/etc/machine-id'
+    sudo rm -f '${IMAGE_ROOTFS}/etc/machine-id'
 }
 
 ROOTFS_POSTPROCESS_COMMAND =+ "image_postprocess_sshd_key_regen"
-- 
2.35.1