From 254583d8b749df9d6c2fe90de227b0cc115376db Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timoth=C3=A9e=20Ravier?= <tim@siosm.fr>
Date: Fri, 26 Jan 2024 11:16:51 +0100
Subject: [PATCH] docs: Add generic container image configuration support

See: https://github.com/coreos/rpm-ostree/pull/4703
See: https://github.com/ostreedev/ostree-rs-ext/pull/567
See: https://github.com/opencontainers/image-spec/blob/main/config.md
Fixes: https://github.com/coreos/rpm-ostree/issues/4712
---
 docs/container.md | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/docs/container.md b/docs/container.md
index d80b9ccec4..2301d26807 100644
--- a/docs/container.md
+++ b/docs/container.md
@@ -157,6 +157,39 @@ for historical reasons.
 $ rpm-ostree compose image  --initialize-mode=if-not-exists --format=registry workstation-ostree-config/fedora-silverblue.yaml quay.io/example/exampleos:latest
 ```
 
+## Adding container image configuration
+
+By default, the `rpm-ostree compose image` command creates containers with a
+minimal config. It notably does not include a default command or entrypoint.
+
+To add more configuration to the created OCI images, you can pass an image
+configuration JSON document via the `--image-config=` argument.
+
+Example image configuration JSON (`config.json`):
+
+```
+{
+    "Env": [
+        "FOO=BAR",
+    ],
+    "Cmd": [
+        "/bin/bash"
+    ],
+    "Labels": {
+        "license": "MIT",
+    }
+}
+```
+
+Example `rpm-ostree compose image` command:
+
+```
+rpm-ostree compose image --initialize --format=ociarchive --image-config=config.json manifest.yaml image.ociarchive
+```
+
+You can find the reference for the image configuration JSON format in the
+[OCI Image Format Specification](https://github.com/opencontainers/image-spec/blob/main/config.md).
+
 ## Converting OSTree commits to new base images
 
 The ostree-container model creates a bidirectional bridge between ostree and OCI