diff --git a/engine/userguide/networking/index.md b/engine/userguide/networking/index.md index bcb7f94812..acea6ce8c0 100644 --- a/engine/userguide/networking/index.md +++ b/engine/userguide/networking/index.md @@ -525,16 +525,16 @@ network and user-defined bridge networks. - You expose ports using the `EXPOSE` keyword in the Dockerfile or the `--expose` flag to `docker run`. Exposing ports is a way of documenting which - ports are used, but does not actually map or open any ports. Exposing ports + ports are used, but **does not actually map or open any ports**. Exposing ports is optional. -- You publish ports using the `PUBLISH` keyword in the Dockerfile or the - `--publish` flag to `docker run`. This tells Docker which ports to open on the - container's network interface. When a port is published, it is mapped to an +- You publish ports using the `--publish` or `--publish-all` flag to `docker run`. + This tells Docker which ports to open on the container's network interface. + When a port is published, it is mapped to an available high-order port (higher than `30000`) on the host machine, unless you specify the port to map to on the host machine at runtime. You cannot - specify the port to map to on the host machine in the Dockerfile, because - there is no way to guarantee that the port will be available on the host - machine where you run the image. + specify the port to map to on the host machine when you build the image (in the + Dockerfile), because there is no way to guarantee that the port will be available + on the host machine where you run the image. This example publishes port 80 in the container to a random high port (in this case, `32768`) on the host machine. The `-d` flag causes the