(docs): Update plain bundle docs

Signed-off-by: Bryce Palmer <bpalmer@redhat.com>

docs/bundles/plain.md

@@ -2,43 +2,151 @@
 
 ## Overview
 
-This document is meant to define the `plain` bundle format as a reference for those publishing `plain` bundles
-for use with RukPak. For more information on the concept of a bundle, click [here](https://github.com/operator-framework/rukpak#bundle).
+This document is meant to define the plain bundle format as a reference for those publishing plain bundles for use with
+RukPak. A bundle is a collection of Kubernetes resources that are packaged together for the purposes of installing onto
+a Kubernetes cluster.
+
+Users can specify a resource bundle to unpack or install via the
+[`Bundle`](https://github.com/operator-framework/rukpak#bundle)
+and [`BundleDeployment`](https://github.com/operator-framework/rukpak#bundledeployment) resources.
+Controllers, called provisioners, consume the bundle referenced in the `Bundle(Deployment)` resource and store or apply the embedded manifests
+
+A plain bundle is a static collection of arbitrary Kubernetes YAML manifests. These manifests are contained in a directory
+that can be packaged in a container image layer , a `git` repository or any other content source that the
+[plain bundle provisioner](../provisioners/plain.md) supports.
+
+Supported source types for a plain bundle currently include the following:
+
+* A directory in a [container image](../sources/image.md)
+* A directory in a [`git` repository](../sources/git.md)
+* A set of keys in a [`ConfigMap`](../sources/local.md)
+* An [upload](../sources/upload.md)
+* A `.tgz` file returned by a [http endpoint](../sources/http.md)
 
-A plain bundle is simply a collection of static, arbitrary, Kubernetes YAML manifests in a given directory.
 
 The currently implemented plain bundle format is the `plain+v0` format. The name of the bundle format, `plain+v0`
-combines the type of bundle (plain) with the current schema version (v0).
+combines the type of bundle (plain) with the current schema version (v0). The
+[plain bundle provisioner](../provisioners/plain.md) is able to source
+`plain+v0` bundles and install them onto a Kubernetes cluster.
 
-> Note: the plain+v0 bundle format is at schema version v0, which means it's an experimental format that is subject
+> Note: the `plain+v0` bundle format is at schema version v0, which means it's an experimental format that is subject
 > to change.
 
-## Example
+## Common Terminology
+
+* *bundle* is a collection of Kubernetes manifests that define content to be deployed to a cluster
+* *bundle image* is a container image that contains a bundle within its filesystem
+* *bundle git repo* is a git repository that contains a bundle within a directory
+
+## Technical Details
+
+* The [plain bundle provisioner](../provisioners/plain.md) is opinionated and expects the
+plain bundle to be located in the root-level `/manifests` directory.
+* The manifests directory should be flat: all manifests should be at the top-level with no subdirectories.
+* It is required that `kubectl apply` is able to process all .yaml files in the directory that make up a plain bundle. For example,
+multi-object YAML files are acceptable, but Ansible playbooks would not be.
 
-For example, below is an example of a file tree in a `plain+v0` bundle. It must have a `manifests` directory contains
-the Kubernetes resources required to deploy an application.
+## Building a plain bundle
+### Prerequisites
 
-```tree
+In order to create a plain bundle for RukPak, ensure your Kubernetes manifests are in a flat directory at the root of
+your project called `manifests/`. This allows the contents to be sourced and unpacked by the
+[plain provisioner](..provisioners/plain.md). It should look similar to:
+
+```bash
+$ tree manifests
 manifests
 ├── namespace.yaml
+├── service_account.yaml
 ├── cluster_role.yaml
-├── role.yaml
-├── serviceaccount.yaml
 ├── cluster_role_binding.yaml
-├── role_binding.yaml
 └── deployment.yaml
 ```
 
 > Note: there must be at least one resource in the manifests directory in order for the bundle to be a valid
-> plain+v0 bundle.
+> `plain+v0` bundle.
 
-## Technical Details
+If you are using [kustomize](https://kustomize.io/) for building your manifests from templates, redirect the output into a single file under the `manifests/` directory. For example:
+```bash
+$ tree templates
+templates
+├── namespace.yaml
+├── service_account.yaml
+├── cluster_role.yaml
+├── cluster_role_binding.yaml
+├── deployment.yaml.yaml
+└── kustomization.yaml
+```
 
-* The static manifests must be located in the /manifests directory for the bundle to be a
-valid `plain+v0` bundle that the provisioner can unpack. A plain bundle image without a /manifests directory is
-invalid and will not be successfully unpacked onto the cluster.
-* The manifests directory should be flat: all manifests should be at the top-level with no subdirectories.
-* Including any content in the /manifests directory of a plain bundle that is not static manifests will result in
-a failure when creating content on-cluster from that bundle. Essentially, any file that would not
-successfully `kubectl apply` will result in an error, but multi-object YAML files, or JSON files, are fine. There will
-be validation tooling provided that can determine whether a given artifact is a valid bundle.
+```bash
+kustomize build templates > manifests/manifests.yaml
+```
+
+### Git source
+
+For using the bundle with a [`git` source](../sources/git.md), commit your `manifests/` directory to your `git` repository.
+
+### HTTP source
+
+For using the bundle with a [HTTP source](../sources/http.md), create a `.tgz` file that contains the `manifests/` directory and its manifests. This `.tgz` file should be served when hitting the HTTP endpoint.
+
+### Image source
+
+For using the bundle with an [image source](../sources/image.md), follow the below steps:
+
+1. Create a Dockerfile at the root of the project
+```bash
+touch Dockerfile.plainbundle
+```
+
+2. Edit the Dockerfile to include the following:
+```bash
+cat <<EOF >Dockerfile.plainbundle
+FROM scratch
+COPY manifests /manifests
+EOF
+```
+
+> Note: The Dockerfile can have any `FROM ...` directive, but it is recommended to use the `FROM scratch`
+> directive to keep the resulting image size minimal
+
+3. Build an OCI-compliant image using any build tooling you prefer. Use an image tag that references a repository that you have push access to. For example,
+
+```bash
+docker build -f Dockerfile.plainbundle -t quay.io/operator-framework/rukpak:example .
+```
+
+4. Push the image to the remote registry
+
+```bash
+docker push quay.io/operator-framework/rukpak:example
+```
+
+If you are looking to use a private image registry for sourcing your bundle content, see the ["Private image registries" section of the image source documentation](../sources/image.md#private-image-registries)
+
+### Upload source
+
+For using the bundle with an [upload source](../sources/upload.md), follow the below steps:
+
+1. Download the `rukpakctl` CLI tool
+```bash
+go install github.com/operator-framework/rukpak/cmd/rukpakctl
+```
+
+2. Ensure RukPak is running. For more info on how to install RukPak on your cluster see the [Installation section of the README](../../README.md#installation)
+
+3. Use `rukpakctl` to create a `BundleDeployment` using the `manifests/` directory
+```bash
+rukpakctl run <bundle-name> .
+```
+
+### ConfigMap source
+
+For using the bundle with a [`ConfigMap` source (also known as a local source)](../sources/local.md), follow the below steps:
+
+1. Ensure RukPak is running. For more info on how to install RukPak on your cluster see the [Installation section of the README](../../README.md#installation)
+
+2. Create a `ConfigMap` from the `manifests/` directory
+```bash
+kubectl create configmap my-configmap --from-file=manifests -n rukpak-system
+```