More random docs

docs/customizing.md

@@ -0,0 +1,42 @@
+# Custom Images
+
+RancherOS image can be easily remaster using a docker build.
+For example, to add `cowsay` to RancherOS you would use the
+following Dockerfile
+
+## Docker image
+
+```Dockerfile
+FROM rancher/os2:v0.0.1-test01
+RUN zypper install -y cowsay
+
+# IMPORTANT: Setup rancheros-release used for versioning/upgrade. The
+# values here should reflect the tag of the image being built
+ARG IMAGE_REPO=norepo
+ARG IMAGE_TAG=latest
+RUN echo "IMAGE_REPO=${IMAGE_REPO}"          > /usr/lib/rancheros-release && \
+    echo "IMAGE_TAG=${IMAGE_TAG}"           >> /usr/lib/rancheros-release && \
+    echo "IMAGE=${IMAGE_REPO}:${IMAGE_TAG}" >> /usr/lib/rancheros-release
+```
+
+And then the following commands
+
+```bash
+docker build --build-arg IMAGE_REPO=myrepo/custom-build \
+             --build-arg IMAGE_TAG=v1.1.1 \
+             -t myrepo/custom-build:v1.1.1 .
+docker push myrepo/custom-build:v1.1.1
+```
+
+## Bootable images
+
+To create bootable images from the docker image you just created
+run the below command
+
+```bash
+curl -o ros-image-build https://raw.githubusercontent.com/rancher/os2/main/ros-image-build
+bash ros-image myrepo/custom-build:v1.1.1 qcow,iso,ami
+```
+
+The above command will create an ISO, a qcow image, and publish AMIs. You need not create all
+three types and can change to comma seperated list to the types you care for.