# App settings

> The environment variables hello-kubernetes reads, for running the image without the Helm chart.

The app reads its settings from environment variables. The Helm chart sets them for you from its [values](https://paulbouwer.github.io/hello-kubernetes/docs/configure/values.md). Use them directly when you run the image another way: with `docker run`, in your own manifests, or by patching the release file [with Kustomize](https://paulbouwer.github.io/hello-kubernetes/docs/deploy/kustomize.md#what-each-chart-value-changes).

| Variable | Default | What it does |
| - | - | - |
| `MESSAGE` | `Hello world!` | The message on the page. Chart value: `message`. |
| `PORT` | `8080` | The port the app listens on. Chart value: `deployment.container.port`. |
| `HANDLER_PATH_PREFIX` | none | The path the app serves under, such as `/app/hello`. Set it when the proxy passes the prefix on. Chart value: `pathPrefix`, when `rewritePath` is `false`. |
| `RENDER_PATH_PREFIX` | none | The path the page’s links use, so the browser asks the proxy for the stylesheet and images under the prefix. Chart value: `pathPrefix`. |
| `KUBERNETES_NAMESPACE` | `-` | The namespace shown on the page. The chart sets it from the pod. |
| `KUBERNETES_POD_NAME` | the host name | The pod shown on the page. The chart sets it from the pod. |
| `KUBERNETES_NODE_NAME` | `-` | The node shown on the page, with its operating system and kernel. The chart sets it from the pod. |
| `CONTAINER_IMAGE` | the app’s image | The image shown on the page. Chart value: `deployment.container.image.*`. |
| `LOG_LEVEL` | `info` | The log level, such as `debug`, `info`, `warn` or `error`. At `debug`, the app logs its settings when it starts. |

Leading and trailing slashes in the two path prefixes are optional. The page also shows the image’s architecture, such as `linux/amd64`, which the app reads from itself.

## The pod details

The chart sets the three `KUBERNETES_` variables with the [Downward API](https://kubernetes.io/docs/concepts/workloads/pods/downward-api/). In your own manifest:

*File: deployment.yaml (part)*

```yaml
env:
  - name: KUBERNETES_NAMESPACE
    valueFrom:
      fieldRef:
        fieldPath: metadata.namespace
  - name: KUBERNETES_POD_NAME
    valueFrom:
      fieldRef:
        fieldPath: metadata.name
  - name: KUBERNETES_NODE_NAME
    valueFrom:
      fieldRef:
        fieldPath: spec.nodeName
```

## Run it with Docker

```bash
docker run --rm -p 8080:8080 -e MESSAGE="Hello from Docker" paulbouwer/hello-kubernetes:1.11.0
```

Open `http://localhost:8080/`. You see **Hello from Docker**, with `-` for the namespace and node, and the container ID as the pod. Press Ctrl+C to stop.

## What the app serves

| Path | What |
| - | - |
| `/` | The page. Under a prefix, `<prefix>/`. |
| `/css/`, `/images/`, `/fonts/`, `/favicon.ico` | The stylesheet, the logo, the Ubuntu font and its licence, and the icon. |

There is no separate health endpoint. The chart’s probes ask for the page.