# Traefik & Docker

A Story of Labels & Containers
{: .subtitle }

![Docker](../assets/img/providers/docker.png)

Attach labels to your containers and let Traefik do the rest!

Traefik works with both [Docker (standalone) Engine](https://docs.docker.com/engine/)
and [Docker Swarm Mode](https://docs.docker.com/engine/swarm/).

!!! tip "The Quick Start Uses Docker"
    If you haven't already, maybe you'd like to go through the [quick start](../getting-started/quick-start.md) that uses the docker provider!

## Configuration Examples

??? example "Configuring Docker & Deploying / Exposing Services"

    Enabling the docker provider
    
    ```toml tab="File (TOML)"
    [providers.docker]
    ```
    
    ```yaml tab="File (YAML)"
    providers:
      docker: {}
    ```
    
    ```bash tab="CLI"
    --providers.docker=true
    ```

    Attaching labels to containers (in your docker compose file)

    ```yaml
    version: "3"
    services:
      my-container:
        # ...
        labels:
          - traefik.http.routers.my-container.rule=Host(`example.com`)
    ```

??? example "Configuring Docker Swarm & Deploying / Exposing Services"

    Enabling the docker provider (Swarm Mode)

    ```toml tab="File (TOML)"
    [providers.docker]
      # swarm classic (1.12-)
      # endpoint = "tcp://127.0.0.1:2375"
      # docker swarm mode (1.12+)
      endpoint = "tcp://127.0.0.1:2377"
      swarmMode = true
    ```
    
    ```yaml tab="File (YAML)"
    providers:
      docker:
        # swarm classic (1.12-)
        # endpoint = "tcp://127.0.0.1:2375"
        # docker swarm mode (1.12+)
        endpoint: "tcp://127.0.0.1:2375"
        swarmMode: true
    ```
    
    ```bash tab="CLI"
    --providers.docker.endpoint=tcp://127.0.0.1:2375
    --providers.docker.swarmMode=true
    ```

    Attach labels to services (not to containers) while in Swarm mode (in your docker compose file)

    ```yaml
    version: "3"
    services:
      my-container:
        deploy:
          labels:
            - traefik.http.routers.my-container.rule=Host(`example.com`)
            - traefik.http.services.my-container-service.loadbalancer.server.port=8080
    ```

## Routing Configuration

When using Docker as a [provider](./overview.md),
Traefik uses [container labels](https://docs.docker.com/engine/reference/commandline/run/#set-metadata-on-container--l---label---label-file) to retrieve its routing configuration.

See the list of labels in the dedicated [routing](../routing/providers/docker.md) section.

### Routing Configuration with Labels

By default, Traefik watches for [container level labels](https://docs.docker.com/config/labels-custom-metadata/) on a standalone Docker Engine.

When using Docker Compose, labels are specified by the directive
[`labels`](https://docs.docker.com/compose/compose-file/#labels) from the
["services" objects](https://docs.docker.com/compose/compose-file/#service-configuration-reference).

!!! tip "Not Only Docker"
    Please note that any tool like Nomad, Terraform, Ansible, etc.
    that is able to define a Docker container with labels can work
    with Traefik & the Docker provider.

### Port Detection

Traefik retrieves the private IP and port of containers from the Docker API.

Ports detection works as follows:

- If a container [exposes](https://docs.docker.com/engine/reference/builder/#expose) only one port,
  then Traefik uses this port for private communication.
- If a container [exposes](https://docs.docker.com/engine/reference/builder/#expose) multiple ports,
  or does not expose any port, then you must manually specify which port Traefik should use for communication 
  by using the label `traefik.http.services.<service_name>.loadbalancer.server.port`
  (Read more on this label in the dedicated section in [routing](../routing/providers/docker.md#port)).

### Host networking

When exposing containers that are configured with [host networking](https://docs.docker.com/network/host/),
the IP address of the host is resolved as follows:

<!-- TODO: verify and document the swarm mode case with container.Node.IPAddress coming from the API -->
- try a lookup of `host.docker.internal`
- otherwise fall back to `127.0.0.1`

On Linux, (and until [github.com/moby/moby/pull/40007](https://github.com/moby/moby/pull/40007) is included in a release),
for `host.docker.internal` to be defined, it should be provided as an `extra_host` to the Traefik container,
using the `--add-host` flag. For example, to set it to the IP address of the bridge interface (docker0 by default):
`--add-host=host.docker.internal:172.17.0.1`

### Docker API Access

Traefik requires access to the docker socket to get its dynamic configuration.

You can specify which Docker API Endpoint to use with the directive [`endpoint`](#endpoint).

!!! warning "Security Note"

    Accessing the Docker API without any restriction is a security concern:
    If Traefik is attacked, then the attacker might get access to the underlying host.
    {: #security-note }
    
    As explained in the Docker documentation: ([Docker Daemon Attack Surface page](https://docs.docker.com/engine/security/security/#docker-daemon-attack-surface)):

    !!! quote
        [...] only **trusted** users should be allowed to control your Docker daemon [...]

    ??? success "Solutions"

        Expose the Docker socket over TCP or SSH, instead of the default Unix socket file.
        It allows different implementation levels of the [AAA (Authentication, Authorization, Accounting) concepts](https://en.wikipedia.org/wiki/AAA_(computer_security)), depending on your security assessment:

        - Authentication with Client Certificates as described in ["Protect the Docker daemon socket."](https://docs.docker.com/engine/security/https/)
        - Authorize and filter requests to restrict possible actions with [the TecnativaDocker Socket Proxy](https://github.com/Tecnativa/docker-socket-proxy).
        - Authorization with the [Docker Authorization Plugin Mechanism](https://web.archive.org/web/20190920092526/https://docs.docker.com/engine/extend/plugins_authorization/)
        - Accounting at networking level, by exposing the socket only inside a Docker private network, only available for Traefik.
        - Accounting at container level, by exposing the socket on a another container than Traefik's.
          With Swarm mode, it allows scheduling of Traefik on worker nodes, with only the "socket exposer" container on the manager nodes.
        - Accounting at kernel level, by enforcing kernel calls with mechanisms like [SELinux](https://en.wikipedia.org/wiki/Security-Enhanced_Linux), to only allows an identified set of actions for Traefik's process (or the "socket exposer" process).
        - SSH public key authentication (SSH is supported with Docker > 18.09)

    ??? info "More Resources and Examples"
        - ["Paranoid about mounting /var/run/docker.sock?"](https://medium.com/@containeroo/traefik-2-0-paranoid-about-mounting-var-run-docker-sock-22da9cb3e78c)
        - [Traefik and Docker: A Discussion with Docker Captain, Bret Fisher](https://blog.containo.us/traefik-and-docker-a-discussion-with-docker-captain-bret-fisher-7f0b9a54ff88)
        - [KubeCon EU 2018 Keynote, Running with Scissors, from Liz Rice](https://www.youtube.com/watch?v=ltrV-Qmh3oY)
        - [Don't expose the Docker socket (not even to a container)](https://www.lvh.io/posts/dont-expose-the-docker-socket-not-even-to-a-container/)
        - [A thread on Stack Overflow about sharing the `/var/run/docker.sock` file](https://news.ycombinator.com/item?id=17983623)
        - [To DinD or not to DinD](https://blog.loof.fr/2018/01/to-dind-or-not-do-dind.html)
        - [Traefik issue GH-4174 about security with Docker socket](https://github.com/containous/traefik/issues/4174)
        - [Inspecting Docker Activity with Socat](https://developers.redhat.com/blog/2015/02/25/inspecting-docker-activity-with-socat/)
        - [Letting Traefik run on Worker Nodes](https://blog.mikesir87.io/2018/07/letting-traefik-run-on-worker-nodes/)
        - [Docker Socket Proxy from Tecnativa](https://github.com/Tecnativa/docker-socket-proxy)

## Docker Swarm Mode

To enable Docker Swarm (instead of standalone Docker) as a configuration provider,
set the [`swarmMode`](#swarmmode) directive to `true`.

### Routing Configuration with Labels

While in Swarm Mode, Traefik uses labels found on services, not on individual containers.

Therefore, if you use a compose file with Swarm Mode, labels should be defined in the
[`deploy`](https://docs.docker.com/compose/compose-file/#labels-1) part of your service.

This behavior is only enabled for docker-compose version 3+ ([Compose file reference](https://docs.docker.com/compose/compose-file)).

### Port Detection

Docker Swarm does not provide any [port detection](#port-detection) information to Traefik.

Therefore you **must** specify the port to use for communication by using the label `traefik.http.services.<service_name>.loadbalancer.server.port`
(Check the reference for this label in the [routing section for Docker](../routing/providers/docker.md#port)).

### Docker API Access

Docker Swarm Mode follows the same rules as Docker [API Access](#docker-api-access).

As the Swarm API is only exposed on the [manager nodes](https://docs.docker.com/engine/swarm/how-swarm-mode-works/nodes/#manager-nodes), you should schedule Traefik on the Swarm manager nodes by default,
by deploying Traefik with a [constraint](https://success.docker.com/article/using-contraints-and-labels-to-control-the-placement-of-containers) on the node's "role":

```shell tab="With Docker CLI"
docker service create \
  --constraint=node.role==manager \
  #... \
```

```yml tab="With Docker Compose"
version: '3'

services:
  traefik:
    # ...
    deploy:
      placement:
        constraints:
          - node.role == manager
```

!!! tip "Scheduling Traefik on Worker Nodes"
    
    Following the guidelines given in the previous section ["Docker API Access"](#docker-api-access),
    if you expose the Docker API through TCP, then Traefik can be scheduled on any node if the TCP
    socket is reachable.
    
    Please consider the security implications by reading the [Security Note](#security-note).
    
    A good example can be found on [Bret Fisher's repository](https://github.com/BretFisher/dogvscat/blob/master/stack-proxy-global.yml#L124).

## Provider Configuration

### `endpoint`

_Required, Default="unix:///var/run/docker.sock"_

```toml tab="File (TOML)"
[providers.docker]
  endpoint = "unix:///var/run/docker.sock"
```

```yaml tab="File (YAML)"
providers:
  docker:
    endpoint: "unix:///var/run/docker.sock"
```

```bash tab="CLI"
--providers.docker.endpoint=unix:///var/run/docker.sock
```

See the sections [Docker API Access](#docker-api-access) and [Docker Swarm API Access](#docker-api-access_1) for more information.

??? example "Using the docker.sock"

    The docker-compose file shares the docker sock with the Traefik container

    ```yaml
    version: '3'

    services:
      traefik:
         image: traefik:v2.3 # The official v2 Traefik docker image
         ports:
           - "80:80"
         volumes:
           - /var/run/docker.sock:/var/run/docker.sock
    ```

    We specify the docker.sock in traefik's configuration file.

    ```toml tab="File (TOML)"
    [providers.docker]
      endpoint = "unix:///var/run/docker.sock"
      # ...
    ```
    
    ```yaml tab="File (YAML)"
    providers:
      docker:
        endpoint: "unix:///var/run/docker.sock"
         # ...
    ```
    
    ```bash tab="CLI"
    --providers.docker.endpoint=unix:///var/run/docker.sock
    # ...
    ```

??? example "Using SSH"

    Using Docker 18.09+ you can connect Traefik to daemon using SSH
    We specify the SSH host and user in Traefik's configuration file.
    Note that is server requires public keys for authentication you must have those accessible for user who runs Traefik.

    ```toml tab="File (TOML)"
    [providers.docker]
      endpoint = "ssh://traefik@192.168.2.5:2022"
      # ...
    ```
    
    ```yaml tab="File (YAML)"
    providers:
      docker:
        endpoint: "ssh://traefik@192.168.2.5:2022"
         # ...
    ```
    
    ```bash tab="CLI"
    --providers.docker.endpoint=ssh://traefik@192.168.2.5:2022
    # ...
    ```

### `useBindPortIP`

_Optional, Default=false_

```toml tab="File (TOML)"
[providers.docker]
  useBindPortIP = true
  # ...
```

```yaml tab="File (YAML)"
providers:
  docker:
    useBindPortIP: true
    # ...
```

```bash tab="CLI"
--providers.docker.useBindPortIP=true
# ...
```

Traefik routes requests to the IP/Port of the matching container.
When setting `useBindPortIP=true`, you tell Traefik to use the IP/Port attached to the container's _binding_ instead of its inner network IP/Port.

When used in conjunction with the `traefik.http.services.<name>.loadbalancer.server.port` label (that tells Traefik to route requests to a specific port),
Traefik tries to find a binding on port `traefik.http.services.<name>.loadbalancer.server.port`.
If it can't find such a binding, Traefik falls back on the internal network IP of the container,
but still uses the `traefik.http.services.<name>.loadbalancer.server.port` that is set in the label.

??? example "Examples of `usebindportip` in different situations."

    | port label         | Container's binding                                | Routes to      |
    |--------------------|----------------------------------------------------|----------------|
    |          -         |           -                                        | IntIP:IntPort  |
    |          -         | ExtPort:IntPort                                    | IntIP:IntPort  |
    |          -         | ExtIp:ExtPort:IntPort                              | ExtIp:ExtPort  |
    | LblPort            |           -                                        | IntIp:LblPort  |
    | LblPort            | ExtIp:ExtPort:LblPort                              | ExtIp:ExtPort  |
    | LblPort            | ExtIp:ExtPort:OtherPort                            | IntIp:LblPort  |
    | LblPort            | ExtIp1:ExtPort1:IntPort1 & ExtIp2:LblPort:IntPort2 | ExtIp2:LblPort |

    !!! info ""
        In the above table:
        
        - `ExtIp` stands for "external IP found in the binding"
        - `IntIp` stands for "internal network container's IP",
        - `ExtPort` stands for "external Port found in the binding"
        - `IntPort` stands for "internal network container's port."

### `exposedByDefault`

_Optional, Default=true_

```toml tab="File (TOML)"
[providers.docker]
  exposedByDefault = false
  # ...
```

```yaml tab="File (YAML)"
providers:
  docker:
    exposedByDefault: false
    # ...
```

```bash tab="CLI"
--providers.docker.exposedByDefault=false
# ...
```

Expose containers by default through Traefik.
If set to false, containers that don't have a `traefik.enable=true` label will be ignored from the resulting routing configuration.

See also [Restrict the Scope of Service Discovery](./overview.md#restrict-the-scope-of-service-discovery).

### `network`

_Optional, Default=empty_

```toml tab="File (TOML)"
[providers.docker]
  network = "test"
  # ...
```

```yaml tab="File (YAML)"
providers:
  docker:
    network: test
    # ...
```

```bash tab="CLI"
--providers.docker.network=test
# ...
```

Defines a default docker network to use for connections to all containers.

This option can be overridden on a container basis with the `traefik.docker.network` label.

### `defaultRule`

_Optional, Default=```Host(`{{ normalize .Name }}`)```_

```toml tab="File (TOML)"
[providers.docker]
  defaultRule = "Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
  # ...
```

```yaml tab="File (YAML)"
providers:
  docker:
    defaultRule: "Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)"
    # ...
```

```bash tab="CLI"
--providers.docker.defaultRule=Host(`{{ .Name }}.{{ index .Labels \"customLabel\"}}`)
# ...
```

For a given container if no routing rule was defined by a label, it is defined by this defaultRule instead.
It must be a valid [Go template](https://golang.org/pkg/text/template/),
augmented with the [sprig template functions](http://masterminds.github.io/sprig/).
The container service name can be accessed as the `Name` identifier,
and the template has access to all the labels defined on this container.

### `swarmMode`

_Optional, Default=false_

```toml tab="File (TOML)"
[providers.docker]
  swarmMode = true
  # ...
```

```yaml tab="File (YAML)"
providers:
  docker:
    swarmMode: true
    # ...
```

```bash tab="CLI"
--providers.docker.swarmMode=true
# ...
```

Activates the Swarm Mode (instead of standalone Docker).

### `swarmModeRefreshSeconds`

_Optional, Default=15_

```toml tab="File (TOML)"
[providers.docker]
  swarmModeRefreshSeconds = 30
  # ...
```

```yaml tab="File (YAML)"
providers:
  docker:
    swarmModeRefreshSeconds: 30
    # ...
```

```bash tab="CLI"
--providers.docker.swarmModeRefreshSeconds=30
# ...
```

Defines the polling interval (in seconds) in Swarm Mode.

### `watch`

_Optional, Default=true_

```toml tab="File (TOML)"
[providers.docker]
  watch = false
  # ...
```

```yaml tab="File (YAML)"
providers:
  docker:
    watch: false
    # ...
```

```bash tab="CLI"
--providers.docker.watch=false
# ...
```

Watch Docker Swarm events.

### `constraints`

_Optional, Default=""_

```toml tab="File (TOML)"
[providers.docker]
  constraints = "Label(`a.label.name`,`foo`)"
  # ...
```

```yaml tab="File (YAML)"
providers:
  docker:
    constraints: "Label(`a.label.name`,`foo`)"
    # ...
```

```bash tab="CLI"
--providers.docker.constraints=Label(`a.label.name`,`foo`)
# ...
```

Constraints is an expression that Traefik matches against the container's labels to determine whether to create any route for that container.
That is to say, if none of the container's labels match the expression, no route for the container is created.
If the expression is empty, all detected containers are included.

The expression syntax is based on the `Label("key", "value")`, and `LabelRegex("key", "value")` functions, as well as the usual boolean logic, as shown in examples below.

??? example "Constraints Expression Examples"

    ```toml
    # Includes only containers having a label with key `a.label.name` and value `foo`
    constraints = "Label(`a.label.name`, `foo`)"
    ```
    
    ```toml
    # Excludes containers having any label with key `a.label.name` and value `foo`
    constraints = "!Label(`a.label.name`, `value`)"
    ```
    
    ```toml
    # With logical AND.
    constraints = "Label(`a.label.name`, `valueA`) && Label(`another.label.name`, `valueB`)"
    ```
    
    ```toml
    # With logical OR.
    constraints = "Label(`a.label.name`, `valueA`) || Label(`another.label.name`, `valueB`)"
    ```
    
    ```toml
    # With logical AND and OR, with precedence set by parentheses.
    constraints = "Label(`a.label.name`, `valueA`) && (Label(`another.label.name`, `valueB`) || Label(`yet.another.label.name`, `valueC`))"
    ```
    
    ```toml
    # Includes only containers having a label with key `a.label.name` and a value matching the `a.+` regular expression.
    constraints = "LabelRegex(`a.label.name`, `a.+`)"
    ```

See also [Restrict the Scope of Service Discovery](./overview.md#restrict-the-scope-of-service-discovery).

### `tls`

_Optional_

#### `tls.ca`

Certificate Authority used for the secured connection to Docker.

```toml tab="File (TOML)"
[providers.docker.tls]
  ca = "path/to/ca.crt"
```

```yaml tab="File (YAML)"
providers:
  docker:
    tls:
      ca: path/to/ca.crt
```

```bash tab="CLI"
--providers.docker.tls.ca=path/to/ca.crt
```

#### `tls.caOptional`

Policy followed for the secured connection with TLS Client Authentication to Docker.
Requires `tls.ca` to be defined.

- `true`: VerifyClientCertIfGiven
- `false`: RequireAndVerifyClientCert
- if `tls.ca` is undefined NoClientCert

```toml tab="File (TOML)"
[providers.docker.tls]
  caOptional = true
```

```yaml tab="File (YAML)"
providers:
  docker:
    tls:
      caOptional: true
```

```bash tab="CLI"
--providers.docker.tls.caOptional=true
```

#### `tls.cert`

Public certificate used for the secured connection to Docker.

```toml tab="File (TOML)"
[providers.docker.tls]
  cert = "path/to/foo.cert"
  key = "path/to/foo.key"
```

```yaml tab="File (YAML)"
providers:
  docker:
    tls:
      cert: path/to/foo.cert
      key: path/to/foo.key
```

```bash tab="CLI"
--providers.docker.tls.cert=path/to/foo.cert
--providers.docker.tls.key=path/to/foo.key
```

#### `tls.key`

Private certificate used for the secured connection to Docker.

```toml tab="File (TOML)"
[providers.docker.tls]
  cert = "path/to/foo.cert"
  key = "path/to/foo.key"
```

```yaml tab="File (YAML)"
providers:
  docker:
    tls:
      cert: path/to/foo.cert
      key: path/to/foo.key
```

```bash tab="CLI"
--providers.docker.tls.cert=path/to/foo.cert
--providers.docker.tls.key=path/to/foo.key
```

#### `tls.insecureSkipVerify`

If `insecureSkipVerify` is `true`, TLS for the connection to Docker accepts any certificate presented by the server and any host name in that certificate.

```toml tab="File (TOML)"
[providers.docker.tls]
  insecureSkipVerify = true
```

```yaml tab="File (YAML)"
providers:
  docker:
    tls:
      insecureSkipVerify: true
```

```bash tab="CLI"
--providers.docker.tls.insecureSkipVerify=true
```