Cannot Connect to docker daemon. is docker daemon running?

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I'm using Jenkins on Docker on my local Mac Machine. And I'm running another Docker on ubuntu VirtualBox. So now, there are 2 docker machines. one is on my mac machine and one is on my Ubuntu VirtualBox machine. I'm running Jenkins on Mac Docker. Now in the Jenkins pipeline, I want to build an image on my ubuntu machine. I've configured Jenkins docker cloud and in the docker host URL, it is connected to the ubuntu docker-machine. But while building a new image, I'm getting the error. Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

I've tried even adding ExecStart=/usr/bin/dockerd -H tcp://0.0.0.0:4243 -H unix:///var/run/docker.sock at /lib/systemd/system/docker.service

WHen i check ps -aux, image

Can someone please help me out? help is appreciated.

docker-machine jenkins-plugins jenkins-pipeline docker jenkins
2 Answers

First personally if I had a setup like that I would not bother connecting to the remote docker and would just install a Jenkins agent on the ubuntu machine and make it talk to the Jenkins master.

But if you want to do it they way you have it set up right now we a Jenkins talking from inside out one docker host into another docker host I suggest looking into the following:

  1. Your Jenkins master and the ubuntu machine a very isolated they might as well just be on different machines not even in the same room. Unix domain sockets, the ones that are identified by unix://* are made for communicating within a single local OS kernel, trying to bridge them into remote machine will lead to disaster.

  2. So the only way Jenkins could communicate to the remote host is via a remote protocol like TCP. Most of the time when you install docker with the default settings it doesn't even listen to TCP at all, mostly for security reasons.

  3. First thing you should do is to configure a docker inside of the ubuntu machine to listen on TCP port and accept connections from remote hosts. You can use netstat -nat to see if anything is listening on TCP 4243. When things are configured correctly you see the line that stats with 0.0.0.0:4243 or something like that in the output of the nestat

  4. Second you need to make sure your the firewalls/iptables/netfilter configuration on the Ubuntu host lets in connections from outside. A good test to try is to telnet <ubuntu-ip> 4243 from a terminal session on your Mac.

  5. Then you need to make sure you that docker networking is configured correctly so that connections from the inside of the container that is running Jenkins end up on your ubuntu box. To test you need to exec -it into your jenkins container and repeat the telnet test. On modern linuxes telnet is usually not installed, so you can use curl -vvv which will always end up with an error, so just look at the verbose output to see if the error because things cannot communicate (timeout, connection reset etc) or the error occurs because your curl tried to talk HTTP to docker and got gibberish response. In the later case you can consider things to be set up correctly.

  6. Finally you need to tell Jenkins Docker to communicate to the remote docker via TCP. Usually that is given on the command line to your docker run, docker ps, docker exec

user_1860990

I've configured it by defining the slave label in my Jenkins Pipeline. Jenkins agents run on a variety of different environments such as physical machines, virtual machines, Kubernetes clusters, and Docker images. In your Jenkins Pipeline or In your JenkinsFile, you've to set the agent accordingly to what you're using either using Docker image or any virtual machine. Also Thank you so much @Vlad, all the things you told me, were really helpful.

user_165849360
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