recipes: add multi-layer OCI example recipes

Add example recipes demonstrating multi-layer OCI image building:

alpine-oci-base_3.19.bb:
  - Fetches Alpine 3.19 from Docker Hub using container-bundle
  - Uses CONTAINER_BUNDLE_DEPLOY for use as OCI_BASE_IMAGE source
  - Pinned digest for reproducible builds

app-container-alpine.bb:
  - Demonstrates external base image usage
  - Layers Yocto packages (busybox) on top of Alpine
  - Uses OCI_IMAGE_CMD for Docker-like behavior

app-container-layered.bb:
  - Demonstrates local base image usage
  - Layers Yocto packages on top of container-base
  - Uses OCI_IMAGE_CMD for Docker-like behavior

Both app containers produce 2-layer OCI images where the base layer
is shared, reducing storage and transfer costs.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

2 files changed, 71 insertions, 0 deletions

diff --git a/recipes-demo/images/app-container-alpine.bb b/recipes-demo/images/app-container-alpine.bb
new file mode 100644
index 00000000..a685f011
--- /dev/null
+++ b/recipes-demo/images/app-container-alpine.bb
@@ -0,0 +1,35 @@
+SUMMARY = "Container image based on Alpine OCI base"
+LICENSE = "MIT"
+LIC_FILES_CHKSUM = "file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
+
+# Use fetched Alpine as base layer
+OCI_BASE_IMAGE = "alpine-oci-base"
+
+# Use CMD (not ENTRYPOINT) so `docker run image /bin/sh` works as expected
+OCI_IMAGE_CMD = "/bin/sh -c 'echo Hello from Alpine-based Yocto container'"
+
+IMAGE_FSTYPES = "container oci"
+inherit image
+inherit image-oci
+
+IMAGE_FEATURES = ""
+IMAGE_LINGUAS = ""
+NO_RECOMMENDATIONS = "1"
+
+# Add Yocto-built packages on top of Alpine
+IMAGE_INSTALL = " \
+       base-files \
+       base-passwd \
+       netbase \
+       busybox \
+"
+
+# Allow build with or without a specific kernel
+IMAGE_CONTAINER_NO_DUMMY = "1"
+
+# Workaround /var/volatile for now
+ROOTFS_POSTPROCESS_COMMAND += "rootfs_fixup_var_volatile ; "
+rootfs_fixup_var_volatile () {
+    install -m 1777 -d ${IMAGE_ROOTFS}/${localstatedir}/volatile/tmp
+    install -m 755 -d ${IMAGE_ROOTFS}/${localstatedir}/volatile/log
+}
diff --git a/recipes-demo/images/app-container-layered.bb b/recipes-demo/images/app-container-layered.bb
new file mode 100644
index 00000000..2762aae1
--- /dev/null
+++ b/recipes-demo/images/app-container-layered.bb
@@ -0,0 +1,36 @@
+SUMMARY = "Layered Application container - test OCI_BASE_IMAGE"
+LICENSE = "MIT"
+LIC_FILES_CHKSUM = "file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
+
+# Use container-base as the base layer
+OCI_BASE_IMAGE = "container-base"
+
+# Use CMD so `docker run image /bin/sh` works as expected
+OCI_IMAGE_CMD = "/bin/sh -c 'echo Hello from layered container'"
+
+IMAGE_FSTYPES = "container oci"
+inherit image
+inherit image-oci
+
+IMAGE_FEATURES = ""
+IMAGE_LINGUAS = ""
+NO_RECOMMENDATIONS = "1"
+
+# Only add packages not in base - this is the "app layer"
+IMAGE_INSTALL = " \
+       base-files \
+       base-passwd \
+       netbase \
+       busybox \
+       curl \
+"
+
+# Allow build with or without a specific kernel
+IMAGE_CONTAINER_NO_DUMMY = "1"
+
+# Workaround /var/volatile for now
+ROOTFS_POSTPROCESS_COMMAND += "rootfs_fixup_var_volatile ; "
+rootfs_fixup_var_volatile () {
+    install -m 1777 -d ${IMAGE_ROOTFS}/${localstatedir}/volatile/tmp
+    install -m 755 -d ${IMAGE_ROOTFS}/${localstatedir}/volatile/log
+}