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问题:

I installed docker-machine 0.1.0 and docker-compose 1.1.0 on Mac OS 10.8.5.
Docker-machine is running normally and able to connect by docker-machine ssh.

$ docker-machine ls NAME   ACTIVE   DRIVER       STATE     URL                         SWARM dev    *        virtualbox   Running   tcp://192.168.99.100:2376

However can't connect from docker-compose.

$ docker-compose up Couldn't connect to Docker daemon at http+unix://var/run/docker.sock - is it running?  If it's at a non-standard location, specify the URL with the DOCKER_HOST environment variable.

My Dockerfile and docker-compose.yml is here.

Dockerfile

FROM centos:centos7 DOCKER_HOST tcp://192.168.99.100:2376

docker-compose.yml

web:   build: .

Why can't connect? Any ideas?

回答1:

The Docker machine is running. But you need to export some environment to connect to the Docker machine. By default, the docker CLI client is trying to communicate to the daemon using http+unix://var/run/docker.sock (as shown in the error message).

Export the correct environment variables using eval $(docker-machine env dev) and then try again. You can also just run docker-machine env dev to see the environment variables it will export. Notice that one of them is DOCKER_HOST, just as the error message suggests you may need to set.

回答2:

Simple solution for me: sudo docker-compose up

UPDATE 2016-3-14: At some point in the docker install process (or docker-compose ?) there is a suggestion and example to add your username to the "docker" group. This allows you to avoid needing "sudo" before all docker commands, like so:

~ > docker run -it ubuntu /bin/bash root@665d1ea76b8d:/# date Mon Mar 14 23:43:36 UTC 2016 root@665d1ea76b8d:/# exit exit ~ >

Look carefully at the output of the install commands (both docker & the 2nd install for docker-compose) and you'll find the necessary step. It is also documented here: https://subosito.com/posts/docker-tips/

Sudo? No!

Tired of typing sudo docker everytime you issue a command? Yeah, there is a way for dealing with that. Although naturally docker is require a root user, we can give a root-equivalent group for docker operations.

You can create a group called docker, then add desired user to that group. After restarting docker service, the user will no need to type sudo each time do docker operations. How it looks like on a shell commands? as a root, here you go:

> sudo groupadd docker > sudo gpasswd -a username docker > sudo service docker restart

Done!

UPDATE 2017-3-9

Docker installation instructions have been updated here.

Post-installation steps for Linux

This section contains optional procedures for configuring Linux hosts to work better with Docker.

Manage Docker as a non-root user

The docker daemon binds to a Unix socket instead of a TCP port. By default that Unix socket is owned by the user root and other users can only access it using sudo. The docker daemon always runs as the root user.

If you don’t want to use sudo when you use the docker command, create a Unix group called docker and add users to it. When the docker daemon starts, it makes the ownership of the Unix socket read/writable by the docker group.

To create the docker group and add your user:

# 1. Create the docker group. $ sudo groupadd docker  # 2. Add your user to the docker group. $ sudo usermod -aG docker $USER  # 3. Log out and log back in so that your group membership is re-evaluated.  # 4. Verify that you can run docker commands without sudo. $ docker run hello-world

This command downloads a test image and runs it in a container. When the container runs, it prints an informational message and exits.

回答3:

By default the docker daemon always runs as the root user, therefore you need to prepend sudo to your Docker command(s).

To create the docker group and add your user:

Create the docker group.

$ sudo groupadd docker
Add your user to the docker group.

$ sudo usermod -aG docker $USER
Log out and log back in so that your group membership is re-evaluated.
Verify that you can docker commands without sudo.

$ docker run hello-world

This command downloads a test image and runs it in a container. When the container runs, it prints an informational message and exits.

The steps outlined above comes from the official Docker documentation.

回答4:

If you are on Linux you may not have docker-machine installed since it is only installed by default on Windows and Mac computers.

If so you will need to got to: https://docs.docker.com/machine/install-machine/ to find instructions for how to install it on your version of Linux.

After installing, retry running docker-compose up before trying anything listed above.

Hope this helps someone. This worked for my devilbox installation in Fedora 25.

回答5:

Anyone checked log ?

In my case error message in /var/log/upstart/docker.log was:

Listening for HTTP on unix (/var/run/docker.sock)  [graphdriver] using prior storage driver "aufs"  Running modprobe bridge nf_nat failed with message: , error: exit status 1  Error starting daemon: Error initializing network controller: Error creating default "bridge" network: can't find an address range for interface "docker0"

Worth to mentioned I had vpn turned on, so: $ sudo service openvpn stop $ sudo service docker restart $ docker-compose up|start $ sudo service openvpn start was the solution.

回答6:

I've had the same symptoms.

Only diff that it happened only during docker-compose build docker ps worked. Happened with version 2.x as well as 3.x. Restarted docker service, then the machine... Even re-installed docker + docker-compose.

Tried everything but nothing helped.

Finally I tried building the Dockerfile "manually" by using docker build.

Apparently I had a permission issue on a file/folder inside the Docker context. It was trying to read the context when starting the build and failed with a proper error message. However this error message did not propagate to docker-compose which only shows Couldn't connect to Docker daemon at http+unix://var/run/docker.sock - is it running?

Having found that the solution was simply adding the file/folder to the .dockerignore file since it wasn't needed for the build. Another solution might have been to chown or chmod it.

Anyway maybe this could help someone coming across the same issue that really has nothing to do with docker and the misleading error message being displayed.

回答7:

Answer from @srfrnk works for me.

In my situation, I had the next docker-compose.yml file:

  nginx:     build:       context: ./       dockerfile: "./docker/nginx.staging/Dockerfile"     depends_on:       - scripts     environment:       NGINX_SERVER_NAME: "some.host"       NGINX_STATIC_CONTENT_OPEN_FILE_CACHE: "off"       NGINX_ERROR_LOG_LEVEL: debug       NGINX_BACKEND_HOST: scripts       NGINX_SERVER_ROOT: /var/www/html     volumes:       - ./docker-runtime/drupal/files:/var/www/html/sites/default/files:rw     ports:       - 80:80

./docker-runtime owner and group - is root when the other files owner - my user. When I tried to build nginx

Couldn't connect to Docker daemon at http+docker://localunixsocket - is it running?

I added ./docker-runtime to .dockerignore and it is solved my problem.

回答8:

sudo systemctl start docker - to start the Docker service.

sudo docker-compose up after that.

I have Fedora 26, and trying to solve the same issue I eventually entered Docker Compose on Fedora Developers' page and then Docker on Fedora Developers' page, which helped me.

Probably, docker service considered by community to start with the system and run in background all the time, but for me it was not so obvious, and that's the reason I can think of why there's no popular answer like this one.

On the Fedora Developers' page there's instruction how to enable Docker to start with the system:

sudo systemctl enable docker