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` part of your service.
If you're in a hurry, maybe you'd rather go through the [static](../reference/static-configuration/overview.md) and the [dynamic](../reference/dynamic-configuration/docker.md) configuration references.
Traefik requires access to the docker socket to get its dynamic configuration.
??? warning "Security Notes"
Depending on your context, accessing the Docker API without any restriction can be a security concern: If Traefik is attacked, then the attacker might get access to the Docker (or Swarm Mode) backend.
As explained in the Docker documentation: ([Docker Daemon Attack Surface page](https://docs.docker.com/engine/security/security/#docker-daemon-attack-surface)):
`[...] only **trusted** users should be allowed to control your Docker daemon [...]`
[TraefikEE](https://containo.us/traefikee) solves this problem by separating the control plane (connected to Docker) and the data plane (handling the requests).
Expose the Docker socket over TCP, 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/)
- Authorization with the [Docker Authorization Plugin Mechanism](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).
When used in conjunction with the `traefik.http.services.XXX.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.XXX.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.XXX.loadbalancer.server.port` that is set in the label.
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", and IntPort stands for "internal network container's port."
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 `LabelRegexp("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`
To update the configuration of the Router automatically attached to the container, add labels starting with `traefik.http.routers.{name-of-your-choice}.` and followed by the option you want to change. For example, to change the rule, you could add the label `traefik.http.routers.my-container.rule=Host(my-domain)`.
To update the configuration of the Service automatically attached to the container, add labels starting with `traefik.http.services.{name-of-your-choice}.`, followed by the option you want to change. For example, to change the passhostheader behavior, you'd add the label `traefik.http.services.{name-of-your-choice}.loadbalancer.passhostheader=false`.
You can declare pieces of middleware using labels starting with `traefik.http.middlewares.{name-of-your-choice}.`, followed by the middleware type/options. For example, to declare a middleware [`redirectscheme`](../middlewares/redirectscheme.md) named `my-redirect`, you'd write `traefik.http.middlewares.my-redirect.redirectscheme.scheme: https`.
If you declare a TCP Router/Service, it will prevent Traefik from automatically creating an HTTP Router/Service (like it does by default if no TCP Router/Service is defined).
If a container is linked to several networks, be sure to set the proper network name (you can check this with `docker inspect <container_id>`), otherwise it will randomly pick one (depending on how docker is returning them).
