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WoJ
Asked: 2016-12-02 05:08:43 +0800 CST

How to edit the options of an existing container?

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I have a container created (docker create) from an image which was using EXPOSE 22 in the Dockerfile

I start it via docker start <container name or ID> and access it via ssh.

I now need to expose one more port, of a service running in this container. I cannot recreate it, it has to have its startup parameters changed in order to expose that extra port. Is this possible?

I was hoping that docker start would allow for the same parameters as docker create or docker run but this is not the case.

Note: I know that the philosophy of docker is to create ephemeral containers. It is a fact of life that I have to deal with this heavily customized container (as opposed to recreating it)

docker

2 Answers

  1. Best Answer

    You're implying you didn't use docker-compose to start it, but a normal docker run. I would look into docker-compose, because then you could have stopped it, and started it again with a new config file. This allows for reproducible creation of a container. All the examples of just using docker run you see everywhere don't help matters.

    In your particular case, I think all you have to do add an iptables rule. By default, dockerd manipulates the iptables rules to redirect traffic (it may even be the only thing EXPOSE does). If you do iptables -t nat -L -n you can probably see how your ports were exposed. You can create a similar rule.

    This does mean that when you restart your server, the rule is gone again. You'll have to save your iptables state. And this then also touches the inconvenience of dockerd manipulating iptables. It's hard to manage next to other services touching iptables (like central configuration systems, fail2ban, or even a simple auto-save of your rules).

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  2. you can open the port in the create command. to open port 80 for example one would run.

    docker create -p 80:80 container/name

    more info can be found on https://docs.docker.com/engine/reference/commandline/create/

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