Simple instruction for build (#688)

build.md

@@ -0,0 +1,47 @@
+# Build luet packages for kairos
+
+kairos uses github action to build packages and push it to quay.io/kairos/packages(amd64 version) or quay.io/kairos/packages-arm64 (arm64 version),
+in case you wanna build it manually, e.g. testing a new added package locally, or create your own repo to serve it offline/privately, it can be done with this steps:
+
+## build packages
+
+To build all packages, go to the repo root dir, and issue commands like this (note, you need to run as root user, otherwise you will get some permission issues):
+
+```shell
+sudo luet build --all --tree packages
+```
+
+To build an individual package, e.g. k8s/k3s-openrc from amd64
+
+```shell
+sudo luet build --values=values/amd64.yaml k8s/k3s-openrc
+```
+
+for arm64 version, the additional args `--backend-args` are needed, e.g.
+
+```shell
+sudo luet --backend-args --load --backend-args --platform --backend-args linux/arm64 build --values=values/arm64.yaml  k8s/k3s-systemd
+```
+
+## Create repo
+
+After packages are build, you may create your repo using luet command, e.g. to create a docker repo for hosting your packages,
+
+```shell
+luet create-repo --type=docker  --output=myorg.org/packages --push-images
+```
+
+After that, you need to push all popluated package into your registry, in this myorg.org
+
+## Consuming the packages
+
+When package is available in registry, it can be used via enabling Kairos add in /etc/luet/luet.yaml as the following:
+
+```yaml
+repositories:
+  - name: "Kairos"
+    type: "docker"
+    enable: true
+    urls:
+    - "myorg.org/packages"
+```