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Is there a command that I can evaluate (eval $COMMAND) or an environment variable that I can inspect to get the URI of the locally running docker host? I need to be this an expression to evaluate at runtime, since I need to use it in a script intended to run on hosts where docker engine may not be running on the standard ports.

Thanks.

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  • The command on local docker host or the pc which run docker daemon & configured to use local docker host? Commented May 17, 2019 at 1:53
  • When from a terminal connected to the localhost I execute docker ps, that command goes to some docker engine. I want to resolve the URI of the daemon that answers to that command. Commented May 17, 2019 at 1:58
  • You should be able to get this from ${DOCKER_HOST} Commented May 17, 2019 at 2:02
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    I thought so; but that variable seems user preference more than docker state handled. I am running docker commands here and echo ${DOCKER_HOST} returns empty. Commented May 17, 2019 at 2:10
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    In my particular case, it is not a remote host, it is the local host. Somehow when I issue docker ..., the docker client knows how to reach a docker engine or fail trying, I just need a command that can evaluate to such URI, maybe even some docker utility? Commented May 17, 2019 at 2:47

2 Answers 2

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I am not sure I have fully understood your question but hopefully this may shed some light.

The docker command is just a REST client. By default the client connects to the unix-socket /var/run/docker.sock to send requests to the docker daemon. You can practically achieve the same thing by running curl:

curl --unix-socket /var/run/docker.sock http:/localhost/version

Now if your docker daemon was configured for remote access, you probably have the URI information in the docker.service service file. See this post How do I find the Docker REST API URL?.

Hope that helps

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Nice! that's exactly what I was looking for. I didn't have very clear how the client addressed the daemon though; but this totally clear things up in the direction I needed, thanks!
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Hey you can use ps command on the host and grep docker like below

>ps aux | grep docker root 1729 0.0 0.3 2222936 56288 ? Ssl May08 8:05 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

then you can get which port(s) or sock it is linked with

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That doesn't give me the URI, nor portions of it reliably; and it most hosts there are plenty of entries in ps matching docker
then grep whole path /usr/bin/dockerd
It doesn't work. If you don't know, that's alright, no need to keep guessing or hacking away until finding something that may stick.

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