Docs: Add reproducible Unikernel examples and build documentation (Nginx, Redis, Httpreply)

Signed-off-by: Nachiket Roy <nachiket.roy.2@gmail.com>

Author: Nachiket-Roy

docs/examples.md

@@ -0,0 +1,32 @@
+# Building Unikernel Images for urunc
+
+This guide demonstrates how to build Unikernel applications and package them as OCI container images so they can be seamlessly deployed over `urunc`.
+
+## Prerequisites
+
+To follow these examples, you must have the following tools available on your host system:
+- **[urunc](https://urunc.io/):** The unikernel container runtime.
+- **[containerd](https://containerd.io/):** The container daemon for managing the images.
+- **[kraftkit](https://unikraft.org/docs/cli):** The Unikraft CLI, used to build the raw unikernel binaries.
+- **Docker:** We use Docker along with the [nubificus/bunny](https://github.com/nubificus/bunny) BuildKit frontend to package the binaries.
+
+## The Building Process
+
+The recommended, robust way to build unikernel images for `urunc` is a two-step process. Rather than writing a monolithic Dockerfile that executes `kraft build` internally (which can cause BuildKit-in-BuildKit nesting issues), we separate the compilation from the packaging:
+
+1. **Compile the Unikernel:** Use standard Unikraft tooling (e.g., `kraft build`) to compile your application into a unikernel binary and generate its corresponding root filesystem (`initrd`).
+2. **Package with Bunny:** Create a `bunnyfile` that points to the compiled binaries. When you run `docker build -f bunnyfile`, the `bunny` frontend kicks in. It takes the binary and rootfs, packages them into a standard OCI container image, and automatically injects all the necessary `com.urunc.unikernel.*` annotations so that `urunc` knows exactly how to execute it.
+
+## Storage Support
+
+`urunc` supports standard container storage patterns. When you package your image using `bunny`, you specify a `rootfs` (typically a `cpio` archive) which `urunc` will mount at runtime as the base filesystem. 
+
+If your application requires persistent data (e.g., a database like Redis), you can also mount additional persistent volumes via standard Kubernetes or `nerdctl` volume mounts. These will be passed through to the unikernel.
+
+## End-to-End Examples
+
+We provide three complete examples of this process:
+
+- [Nginx](../examples/nginx/README.md)
+- [Redis](../examples/redis/README.md)
+- [Httpreply](../examples/httpreply/README.md)

examples/httpreply/README.md

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+# Httpreply Unikernel Example
+
+This example demonstrates how to build and package a simple HTTP reply unikernel using `kraft` and `bunny`.
+
+## Step 1: Compile the Unikernel
+
+First, clone the Unikraft httpreply repository (or a similar simple web server example) and build the binary:
+
+```bash
+git clone https://github.com/unikraft/app-httpreply.git
+cd app-httpreply
+kraft build --target qemu-x86_64
+```
+
+> [!WARNING]
+> The `kraft build` step MUST succeed and produce a valid kernel binary. `bunny` only packages existing files; if the compilation fails or produces an empty file, the resulting OCI image will not be able to boot in `urunc`.
+
+## Step 2: Package with Bunny
+
+Copy the `bunnyfile` from this directory into your project directory, along with the kernel. 
+Since `httpreply` is a simple unikernel, it generally does not require a complex root filesystem, so our `bunnyfile` just uses `scratch`.
+
+For example:
+```bash
+cp /path/to/urunc/examples/httpreply/bunnyfile .
+cp .unikraft/build/httpreply_qemu-x86_64 ./httpreply-qemu-x86_64
+```
+
+Then, build the OCI image using Docker and the `bunny` BuildKit frontend:
+
+```bash
+docker build -f bunnyfile -t urunc-httpreply:latest .
+```
+
+You now have a fully-packaged HTTP unikernel image ready to be run with `urunc`!

examples/httpreply/bunnyfile

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+#syntax=harbor.nbfc.io/nubificus/bunny:latest
+version: v0.1
+platforms:
+  framework: unikraft
+  monitor: qemu
+  architecture: x86_64
+rootfs:
+  from: scratch
+  type: raw
+kernel:
+  from: local
+  path: httpreply-qemu-x86_64
+cmdline: "/httpreply"

examples/nginx/README.md

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+# Nginx Unikernel Example
+
+This example demonstrates how to build and package an Nginx unikernel using `kraft` and `bunny`.
+
+## Step 1: Compile the Unikernel
+
+First, clone the Unikraft Nginx repository and build the binary and rootfs:
+
+```bash
+git clone https://github.com/unikraft/app-nginx.git
+cd app-nginx
+kraft build --target qemu-x86_64
+```
+
+> [!WARNING]
+> The `kraft build` step MUST succeed and produce a valid kernel binary and rootfs. `bunny` only packages existing files; if the compilation fails or produces an empty file, the resulting OCI image will not be able to boot in `urunc`.
+
+After a successful build, you will have the compiled kernel and a root filesystem archive in the output directory.
+
+## Step 2: Package with Bunny
+
+Copy the `bunnyfile` from this directory into your `app-nginx` project directory, along with the kernel and rootfs so they match the paths in the `bunnyfile`.
+
+For example:
+```bash
+cp /path/to/urunc/examples/nginx/bunnyfile .
+cp .unikraft/build/nginx_qemu-x86_64 ./nginx-qemu-x86_64
+cp .unikraft/build/initrd.cpio ./rootfs.cpio
+```
+
+Then, build the OCI image using Docker and the `bunny` BuildKit frontend:
+
+```bash
+docker build -f bunnyfile -t urunc-nginx:latest .
+```
+
+You now have a fully-packaged Nginx unikernel image ready to be run with `urunc`!

examples/nginx/bunnyfile

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+#syntax=harbor.nbfc.io/nubificus/bunny:latest
+version: v0.1
+platforms:
+  framework: unikraft
+  monitor: qemu
+  architecture: x86_64
+rootfs:
+  from: local
+  path: rootfs.cpio
+kernel:
+  from: local
+  path: nginx-qemu-x86_64
+cmdline: "nginx -c /nginx/conf/nginx.conf"

examples/redis/README.md

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+# Redis Unikernel Example
+
+This example demonstrates how to build and package a Redis unikernel using `kraft` and `bunny`.
+
+One of the great features of `bunny` is that it can dynamically create the `initrd` (root filesystem) for you. Instead of dealing with complex build-system hacks to embed `redis.conf`, we can simply tell `bunny` to include our local `redis.conf` in the final image!
+
+## Step 1: Compile the Unikernel
+
+First, clone the Unikraft Redis repository and build the binary:
+
+```bash
+git clone https://github.com/unikraft/app-redis.git
+cd app-redis
+kraft build --target qemu-x86_64
+```
+
+> [!WARNING]
+> The `kraft build` step MUST succeed and produce a valid kernel binary. `bunny` only packages existing files; if the compilation fails or produces an empty file, the resulting OCI image will not be able to boot in `urunc`.
+
+## Step 2: Package with Bunny
+
+Copy the `bunnyfile` from this directory into your `app-redis` project directory, along with the kernel. Create a default `redis.conf` file as well.
+
+For example:
+```bash
+cp /path/to/urunc/examples/redis/bunnyfile .
+cp .unikraft/build/redis_qemu-x86_64 ./redis-qemu-x86_64
+
+# Create a basic redis.conf
+echo "port 6379" > redis.conf
+```
+
+Notice the `rootfs` section in our `bunnyfile`:
+```yaml
+rootfs:
+  from: scratch
+  type: initrd
+  include:
+  - redis.conf:/conf/redis.conf
+```
+This instructs `bunny` to generate a new `initrd` from scratch and embed our local `redis.conf` into `/conf/redis.conf`.
+
+Finally, build the OCI image:
+
+```bash
+docker build -f bunnyfile -t urunc-redis:latest .
+```
+
+You now have a fully-packaged Redis unikernel image ready to be run with `urunc`!

examples/redis/bunnyfile

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+#syntax=harbor.nbfc.io/nubificus/bunny:latest
+version: v0.1
+platforms:
+  framework: unikraft
+  monitor: qemu
+  architecture: x86_64
+rootfs:
+  from: scratch
+  type: initrd
+  include:
+  - redis.conf:/conf/redis.conf
+kernel:
+  from: local
+  path: redis-qemu-x86_64
+cmdline: "redis-server /conf/redis.conf"

mkdocs.yml

@@ -35,6 +35,7 @@ nav:
   - Developer Guide: 
       - developer-guide/*.md
       - API Reference: https://pkg.go.dev/github.com/urunc-dev/urunc/pkg/unikontainers
+  - Examples: examples.md
   - Tutorials:
       - tutorials/*.md