# Interacting with the balena Supervisor

The balena Supervisor is balena's agent that runs on devices. Its main role is to ensure your app is running, and keep communications with the balenaCloud API server.

The Supervisor itself has its own API, with means for user applications to communicate and execute some special actions that affect the host OS or the application itself. There are two main ways for the application to interact with the Supervisor: the update lockfile and the HTTP API.

Only Supervisors after version 1.1.0 have this functionality, and some of the endpoints appeared in later versions (we've noted it down where this is the case). Supervisor version 1.1.0 corresponds to OS images downloaded after October 14th 2015.

## HTTP API reference

The supervisor exposes an HTTP API on port 48484 (`BALENA_SUPERVISOR_PORT`).

**All endpoints require an apikey parameter, which is exposed to the application as `BALENA_SUPERVISOR_API_KEY`.**

The full address for the API, i.e. `"http://127.0.0.1:48484"`, is available as `BALENA_SUPERVISOR_ADDRESS`. **Always use these variables when communicating via the API, since address and port could change**.

Alternatively, the balena API (api.balena-cloud.com) has a proxy endpoint at `POST /supervisor/<url>` (where `<url>` is one of the API URLs described below) from which you can send API commands to the supervisor remotely, using your Auth Token instead of your API key. Commands sent through the proxy can specify either an `appId` to send the request to all devices in an application, or a `deviceId` or `uuid` to send to a particular device. These requests default to POST unless you specify a `method` parameter (e.g. "GET"). In the examples below, we show how to use a uuid to specify a device, but in any of those you can replace `uuid` for a `deviceId` or `appId`.

The API is versioned (currently at v1), except for `/ping`.

You might notice that the formats of some responses differ. This is because they were implemented later, and in Go instead of node.js - even if the Go pieces were later removed, so we kept the response format for backwards compatibility.

Here's the full list of endpoints implemented so far. In all examples, replace everything between `< >` for the corresponding values.

<hr>

### GET /ping

Responds with a simple "OK", signaling that the supervisor is alive and well.

#### Examples:
From the app on the device:
```bash
$ curl -X GET --header "Content-Type:application/json" \
	"$BALENA_SUPERVISOR_ADDRESS/ping?apikey=$BALENA_SUPERVISOR_API_KEY"
```
Response:
```none
OK
```

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>, "method": "GET"}' \
	"https://api.balena-cloud.com/supervisor/ping"
```

<hr>

### POST /v1/blink

Starts a blink pattern on a LED for 15 seconds, if your device has one.
Responds with an empty 200 response. It implements the "identify device" feature from the dashboard.

#### Examples:
From the app on the device:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	"$BALENA_SUPERVISOR_ADDRESS/v1/blink?apikey=$BALENA_SUPERVISOR_API_KEY"
```

(Empty response)

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>}' \
	"https://api.balena-cloud.com/supervisor/v1/blink"
```

<hr>

### POST /v1/update

Triggers an update check on the supervisor. Optionally, forces an update when updates are locked.

Responds with an empty 204 (No Content) response.

#### Request body
Can be a JSON object with a `force` property. If this property is true, the update lock will be overridden.
```json
{
	"force": true
}
```

#### Examples:
From the app on the device:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--data '{"force": true}' \
	"$BALENA_SUPERVISOR_ADDRESS/v1/update?apikey=$BALENA_SUPERVISOR_API_KEY"
```
(Empty response)

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>, "data": {"force": true}}' \
	"https://api.balena-cloud.com/supervisor/v1/update"
```

<hr>

### POST /v1/reboot

Reboots the device. This will first try to stop applications, and fail if there is an update lock.
An optional "force" parameter in the body overrides the lock when true (and the lock can also be overridden from
the dashboard).

When successful, responds with 202 accepted and a JSON object:
```json
{
	"Data": "OK",
	"Error": ""
}
```

#### Request body
Can contain a `force` property, which if set to `true` will cause the update lock to be overridden.

#### Examples:
From the app on the device:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	"$BALENA_SUPERVISOR_ADDRESS/v1/reboot?apikey=$BALENA_SUPERVISOR_API_KEY"
```
Response:
```json
{"Data":"OK","Error":""}
```

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>}' \
	"https://api.balena-cloud.com/supervisor/v1/reboot"
```

<hr>

### POST /v1/shutdown

**Dangerous**. Shuts down the device. This will first try to stop applications, and fail if there is an update lock.
An optional "force" parameter in the body overrides the lock when true (and the lock can also be overridden from
the dashboard).

When successful, responds with 202 accepted and a JSON object:
```json
{
	"Data": "OK",
	"Error": ""
}
```

#### Request body
Can contain a `force` property, which if set to `true` will cause the update lock to be overridden.

#### Examples:
From the app on the device:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	"$BALENA_SUPERVISOR_ADDRESS/v1/shutdown?apikey=$BALENA_SUPERVISOR_API_KEY"
```
Response:

```json
{"Data":"OK","Error":""}
```

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>}' \
	"https://api.balena-cloud.com/supervisor/v1/shutdown"
```

<hr>

### POST /v1/purge

Clears the user application's `/data` folder.

When successful, responds with 200 and a JSON object:
```json
{
	"Data": "OK",
	"Error": ""
}
```

#### Request body
Has to be a JSON object with an `appId` property, corresponding to the ID of the application the device is running.

Example:

```json
{
	"appId": 2167
}
```

#### Examples:
From the app on the device:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--data '{"appId": <appId>}' \
	"$BALENA_SUPERVISOR_ADDRESS/v1/purge?apikey=$BALENA_SUPERVISOR_API_KEY"
```
Response:

```none
{"Data":"OK","Error":""}
```

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>, "data": {"appId": <appId>}}' \
	"https://api.balena-cloud.com/supervisor/v1/purge"
```

<hr>

### POST /v1/restart

Restarts a user application container

When successful, responds with 200 and an "OK"

#### Request body
Has to be a JSON object with an `appId` property, corresponding to the ID of the application the device is running.

Example:

```json
{
	"appId": 2167
}
```

#### Examples:
From the app on the device:

```bash
$ curl -X POST --header "Content-Type:application/json" \
	--data '{"appId": <appId>}' \
	"$BALENA_SUPERVISOR_ADDRESS/v1/restart?apikey=$BALENA_SUPERVISOR_API_KEY"
```

Response:

```none
OK
```

Remotely via the API proxy:

```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>, "data": {"appId": <appId>}}' \
	"https://api.balena-cloud.com/supervisor/v1/restart"
```

### POST /v1/regenerate-api-key

Invalidates the current `BALENA_SUPERVISOR_API_KEY` and generates a new one. Responds with the new API key, but **the application will be restarted on the next update cycle** to update the API key environment variable.

#### Examples:
From the app on the device:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	"$BALENA_SUPERVISOR_ADDRESS/v1/regenerate-api-key?apikey=$BALENA_SUPERVISOR_API_KEY"
```

Response:

```none
480af7bb8a9cf56de8a1e295f0d50e6b3bb46676aaddbf4103aa43cb57039364
```

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>}' \
	"https://api.balena-cloud.com/supervisor/v1/regenerate-api-key"
```

<hr>

### GET /v1/device

Introduced in supervisor v1.6.
Returns the current device state, as reported to the balenaCloud API and with some extra fields added to allow control over pending/locked updates.
The state is a JSON object that contains some or all of the following:
* `api_port`: Port on which the supervisor is listening.
* `commit`: Hash of the current commit of the application that is running.
* `ip_address`: Space-separated list of IP addresses of the device.
* `status`: Status of the device regarding the app, as a string, i.e. "Stopping", "Starting", "Downloading", "Installing", "Idle".
* `download_progress`: Amount of the application image that has been downloaded, expressed as a percentage. If the update has already been downloaded, this will be `null`.
* `os_version`: Version of the host OS running on the device.
* `supervisor_version`: Version of the supervisor running on the device.
* `update_pending`: This one is not reported to the balenaCloud API. It's a boolean that will be true if the supervisor has detected there is a pending update.
* `update_downloaded`: Not reported to the balenaCloud API either. Boolean that will be true if a pending update has already been downloaded.
* `update_failed`: Not reported to the balenaCloud API. Boolean that will be true if the supervisor has tried to apply a pending update but failed (i.e. if the app was locked, there was a network failure or anything else went wrong).

Other attributes may be added in the future, and some may be missing or null if they haven't been set yet.

#### Examples:
From the app on the device:
```bash
$ curl -X GET --header "Content-Type:application/json" \
	"$BALENA_SUPERVISOR_ADDRESS/v1/device?apikey=$BALENA_SUPERVISOR_API_KEY"
```
Response:
```json
{"api_port":48484,"ip_address":"192.168.0.114 10.42.0.3","commit":"414e65cd378a69a96f403b75f14b40b55856f860","status":"Downloading","download_progress":84,"os_version":"Resin OS 1.0.4 (fido)","supervisor_version":"1.6.0","update_pending":true,"update_downloaded":false,"update_failed":false}
```

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>, "method": "GET"}' \
	"https://api.balena-cloud.com/supervisor/v1/device"
```

<hr>

### POST /v1/apps/:appId/stop

Introduced in supervisor v1.8.
Temporarily stops a user application container. A reboot or supervisor restart will cause the container to start again.
The container is not removed with this endpoint.

This is only supported on single-container devices, and will return 400 on devices running multiple containers.

When successful, responds with 200 and the Id of the stopped container.

The appId must be specified in the URL.

#### Request body
Can contain a `force` property, which if set to `true` will cause the update lock to be overridden.

#### Examples:
From the app on the device:

```bash
$ curl -X POST --header "Content-Type:application/json" \
	"$BALENA_SUPERVISOR_ADDRESS/v1/apps/<appId>/stop?apikey=$BALENA_SUPERVISOR_API_KEY"
```

Response:

```json
{"containerId":"5f4d4a857742e9ecac505ba5710834d3852ad7d71e10389fc6f61d8655a21806"}
```

Remotely via the API proxy:

```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>}' \
	"https://api.balena-cloud.com/supervisor/v1/apps/<appId>/stop"
```

<hr>

### POST /v1/apps/:appId/start

Introduced in supervisor v1.8.
Starts a user application container, usually after it has been stopped with `/v1/stop`.

This is only supported on single-container devices, and will return 400 on devices running multiple containers.

When successful, responds with 200 and the Id of the started container.

The appId must be specified in the URL.

#### Examples:
From the app on the device:

```bash
$ curl -X POST --header "Content-Type:application/json" \
	"$BALENA_SUPERVISOR_ADDRESS/v1/apps/<appId>/start?apikey=$BALENA_SUPERVISOR_API_KEY"
```

Response:

```json
{"containerId":"6d9e1efdb9aad90fdb2df911f785b6aa00270e9448e75226a9a7361c8a9500cf"}
```

Remotely via the API proxy:

```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>}' \
	"https://api.balena-cloud.com/supervisor/v1/apps/<appId>/start"
```

<hr>

### GET /v1/apps/:appId

Introduced in supervisor v1.8.
Returns the application running on the device
The app is a JSON object that contains the following:
* `appId`: The id of the app as per the balenaCloud API.
* `commit`: Application commit that is running.
* `imageId`: The docker image of the current application build.
* `containerId`: ID of the docker container of the running app.
* `env`: A key-value store of the app's environment variables.

The appId must be specified in the URL.

This is only supported on single-container devices, and will return 400 on devices running multiple containers.

#### Examples:
From the app on the device:
```bash
$ curl -X GET --header "Content-Type:application/json" \
	"$BALENA_SUPERVISOR_ADDRESS/v1/apps/<appId>?apikey=$BALENA_SUPERVISOR_API_KEY"
```
Response:
```json
{"appId": 3134,"commit":"414e65cd378a69a96f403b75f14b40b55856f860","imageId":"registry.balena-cloud.com/superapp/414e65cd378a69a96f403b75f14b40b55856f860","containerId":"e5c1eace8b4e","env":{"FOO":"bar"}}
```

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>, "method": "GET"}' \
	"https://api.balena-cloud.com/supervisor/v1/apps/<appId>"
```

<hr>

### GET /v1/healthy

Added in supervisor v6.5.0.

Used internally to check whether the supervisor is running correctly, according to some heuristics that help determine
whether the internal components, application updates and reporting to the balenaCloud API are functioning.

Responds with an empty 200 response if the supervisor is healthy, or a 500 status code if something is not working
correctly.

#### Examples:
From the app on the device:
```bash
$ curl "$BALENA_SUPERVISOR_ADDRESS/v1/healthy"
```
(Empty response)

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>, "method": "GET"}' \
	"https://api.balena-cloud.com/supervisor/v1/healthy"
```

<hr>

### PATCH /v1/device/host-config

Added in supervisor v6.6.0.

This endpoint allows setting some configuration values for the host OS. Currently it supports
proxy and hostname configuration.

For proxy configuration, balenaOS 2.0.7 and higher provides a transparent proxy redirector (redsocks) that makes all connections be routed to a SOCKS or HTTP proxy. This endpoint allows user applications to modify these proxy settings at runtime.


#### Request body

Is a JSON object with several optional fields. Proxy and hostname configuration go under a "network" key. If "proxy" or "hostname" are not present (undefined), those values will not be modified, so that a request can modify hostname
without changing proxy settings and viceversa.

```json
{
	"network": {
		"proxy": {
			"type": "http-connect",
			"ip": "myproxy.example.com",
			"port": 8123,
			"login": "username",
			"password": "password",
			"noProxy": [ "152.10.30.4", "253.1.1.0/16" ]
		},
		"hostname": "mynewhostname"
	}
}
```

In the proxy settings, `type`, `ip`, `port`, `login` and `password` are the settings for the proxy redirector to
be able to connnect to the proxy, based on how [redsocks.conf](https://github.com/darkk/redsocks/blob/master/redsocks.conf.example) works. `type` can be `socks4`, `socks5`, `http-connect` or `http-relay` (not all proxies are
guaranteed to work, especially if they block connections that the balena services may require).

Keep in mind that, even if transparent proxy redirection will take effect immediately after the API call (i.e. all new connections will go through the proxy), open connections will not be closed. So, if for example, the device has managed to connect to the balenaCloud VPN without the proxy, it will stay connected directly without trying to reconnect through the proxy, unless the connection breaks - any reconnection attempts will then go through the proxy. To force *all* connections to go through the proxy, the best way is to reboot the device (see the /v1/reboot endpoint). In most networks were no connections to the Internet can be made if not through a proxy, this should not be necessary (as there will be no open connections before configuring the proxy settings).

The "noProxy" setting for the proxy is an optional array of IP addresses/subnets that should not be routed through the
proxy. Keep in mind that local/reserved subnets are already [excluded by balenaOS automatically](https://github.com/resin-os/meta-resin/blob/master/meta-resin-common/recipes-connectivity/resin-proxy-config/resin-proxy-config/resin-proxy-config#L48).

If either "proxy" or "hostname" are null or empty values (i.e. `{}` for proxy or an empty string for hostname), they will be cleared to their default values (i.e. not using a proxy, and a hostname equal to the first 7 characters of the device's uuid, respectively).

#### Examples:
From the app on the device:
```bash
$ curl -X PATCH --header "Content-Type:application/json" \
	--data '{"network": {"hostname": "newhostname"}}' \
	"$BALENA_SUPERVISOR_ADDRESS/v1/device/host-config?apikey=$BALENA_SUPERVISOR_API_KEY"
```

Response:
```none
OK
```

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>, "method": "PATCH", "data": {"network": {"hostname": "newhostname"}}}' \
	"https://api.balena-cloud.com/supervisor/v1/device/host-config"
```

<hr>

### GET /v1/device/host-config

Added in supervisor v6.6.0.

This endpoint allows reading some configuration values for the host OS, previously set with `PATCH /v1/device/host-config`. Currently it supports
proxy and hostname configuration.

Please refer to the PATCH endpoint above for details on the behavior and meaning of the fields in the response.

#### Examples:
From the app on the device:
```bash
$ curl "$BALENA_SUPERVISOR_ADDRESS/v1/device/host-config?apikey=$BALENA_SUPERVISOR_API_KEY"
```

Response:
```json
{"network":{"proxy":{"ip":"192.168.0.199","port":"8123","type":"socks5"},"hostname":"27b0fdc"}}
```

Remotely via the API proxy:
```bash
$ curl -X POST --header "Content-Type:application/json" \
	--header "Authorization: Bearer <auth token>" \
	--data '{"uuid": <uuid>, "method": "GET"}' \
	"https://api.balena-cloud.com/supervisor/v1/device/host-config"
```

### GET /v2/applications/state

Added in supervisor v7.12.0

Get a list of applications, services and their statuses. This will reflect the
current state of the supervisor, and not the target state.

From the user container:
```bash
$ curl "$BALENA_SUPERVISOR_ADDRESS/v2/applications/state?apikey=$BALENA_SUPERVISOR_API_KEY"
```

Response:
```json
{
  "appname": {
    "appId": 1011165,
    "commit": "217d55237092995e4576367e529ebb03",
    "services": {
      "main": {
        "status": "Downloaded",
        "releaseId": 557617,
        "downloadProgress": null
      },
      "frontend": {
        "status": "Downloading",
        "releaseId": 557631,
        "downloadProgress": 0
      },
      "proxy": {
        "status": "Downloaded",
        "releaseId": 557631,
        "downloadProgress": null
      },
      "data": {
        "status": "Downloading",
        "releaseId": 557631,
        "downloadProgress": 7
      },
      "metrics": {
        "status": "Downloading",
        "releaseId": 557631,
        "downloadProgress": 35
      }
    }
  }
}
```