From e721413233f62baca4e60cc47340e8890488637f Mon Sep 17 00:00:00 2001
From: Jonathan Lebon <jonathan@jlebon.com>
Date: Apr 24 2024 19:51:36 +0000
Subject: Add Containerfile to make building locally easier


This is a simplified version of the one in centos-bootc. The focus is
purely on wrapping the rpm-ostree compose step.

Add instructions on how to use this Containerfile.

Copy in the necessary `fedora-bootc-config.json` file from centos-bootc.

---

diff --git a/Containerfile b/Containerfile
new file mode 100644
index 0000000..5eb95eb
--- /dev/null
+++ b/Containerfile
@@ -0,0 +1,20 @@
+# This Containerfile provides a more friendly way to build base images locally.
+# To build this Containerfile, you *must* use podman/buildah. See README.md for
+# details. For more information about the techniques used here, see the CentOS
+# equivalent of this approach:
+#
+# https://github.com/CentOS/centos-bootc/blob/main/Containerfile.centos-stream9
+
+# This is just a convenient image which has rpm-ostree in it.
+FROM quay.io/centos-bootc/bootc-image-builder:latest as builder
+COPY . /src
+WORKDIR /src
+RUN --mount=type=cache,target=/workdir \
+    --mount=type=bind,rw=true,src=.,dst=/buildcontext,bind-propagation=shared \
+      rpm-ostree compose image \
+        --image-config fedora-bootc-config.json --cachedir=/workdir --format=ociarchive --initialize fedora-bootc.yaml /buildcontext/out.ociarchive
+
+FROM oci-archive:./out.ociarchive
+# Need to reference builder here to force ordering. But since we have to run
+# something anyway, we might as well cleanup after ourselves.
+RUN --mount=type=bind,from=builder,src=.,target=/var/tmp --mount=type=bind,rw=true,src=.,dst=/buildcontext,bind-propagation=shared rm /buildcontext/out.ociarchive
diff --git a/README.md b/README.md
index 6e7bd17..7479717 100644
--- a/README.md
+++ b/README.md
@@ -4,8 +4,31 @@ This repo contains the definition files for the base Fedora bootable container.
 Note that while the repo is currently hosted under the `fedora-iot` namespace,
 it is not tied to the IoT use case; these are generic base images.
 
-The images here are built in Fedora by pungi and pushed to
-quay.io/fedora/fedora-bootc.
+The images here are built in Fedora by [pungi](https://pagure.io/pungi/) and
+pushed to quay.io/fedora/fedora-bootc.
+
+## Building
+
+While the canonical images built in pungi directly call
+[rpm-ostree](https://github.com/coreos/rpm-ostree), we also provide a
+`Containerfile` to make it convenient for anyone to build these images locally
+using only podman or buildah. Full privileges must be provided:
+
+```
+podman build --security-opt=label=disable --cap-add=all \
+  --device /dev/fuse -t localhost/fedora-bootc .
+```
+
+## Customizing
+
+The easiest way to customize the image is by adding more directives to the
+`Containerfile` in the last stage of the build (e.g. `COPY`ing files, or
+`RUN`ning commands).
+
+It is also possible to modify the rpm-ostree treefiles directly, though that
+approach is expected to lose relevance in the future. The treefile format is
+documented [here](https://coreos.github.io/rpm-ostree/treefile/). You will most
+likely be interested in the `packages` and `postprocess` keys.
 
 ## Motivation
 
diff --git a/fedora-bootc-config.json b/fedora-bootc-config.json
new file mode 100644
index 0000000..f5429f9
--- /dev/null
+++ b/fedora-bootc-config.json
@@ -0,0 +1,9 @@
+{
+    "Labels": {
+        "containers.bootc": "1",
+        "bootc.diskimage-builder": "quay.io/centos-bootc/bootc-image-builder",
+        "redhat.id": "fedora",
+        "redhat.version-id": "40"
+    },
+    "StopSignal": "SIGRTMIN+3"
+}