Exposing Docker containers: port mapping with -p and -P

Andrew Dorokhov schedule 1 min read

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`-p` — explicit port mapping

docker run -d -p 8000:80 nginx
curl localhost:8000

-p 8000:80 maps host port 8000 to container port 80.

With -P, Docker picks a free host port for each EXPOSEd container port:

ID=$(docker run -d -P nginx)
docker port $ID 80
curl localhost:32771

Useful when you run many containers with exposed ports and do not want to assign host ports manually. Check assignments with docker port.

-P, --publish-all

Publish all container ports to the host. Docker assigns a high, free host port for each exposed port.

--expose

Like Dockerfile EXPOSE: documents ports for the container but does not publish them. Meaningful with -P or when linking containers .

code

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