The Basics

Starting Docker

If you have used one of the quick install paths', Docker may have been installed with upstart, Ubuntu's system for starting processes at boot time. You should be able to run docker help and get output.

If you get docker: command not found or something like /var/lib/docker/repositories: permission denied you will need to specify the path to it and manually start it.

# Run docker in daemon mode
sudo <path to>/docker -d &

Running an interactive shell

# Download a base image
docker pull base

# Run an interactive shell in the base image,
# allocate a tty, attach stdin and stdout
docker run -i -t base /bin/bash

Bind Docker to another host/port or a unix socket

With -H it is possible to make the Docker daemon to listen on a specific ip and port. By default, it will listen on 127.0.0.1:4243 to allow only local connections but you can set it to 0.0.0.0:4243 or a specific host ip to give access to everybody.

Similarly, the Docker client can use -H to connect to a custom port.

-H accepts host and port assignment in the following format: tcp://[host][:port] or unix://path For example:

tcp://host -> tcp connection on host:4243
tcp://host:port -> tcp connection on host:port
tcp://:port -> tcp connection on 127.0.0.1:port
unix://path/to/socket -> unix socket located at path/to/socket

# Run docker in daemon mode
sudo <path to>/docker -H 0.0.0.0:5555 -d &
# Download a base image
docker -H :5555 pull base

You can use multiple -H, for example, if you want to listen on both tcp and a unix socket

# Run docker in daemon mode
sudo <path to>/docker -H tcp://127.0.0.1:4243 -H unix:///var/run/docker.sock -d &
# Download a base image
docker pull base
# OR
docker -H unix:///var/run/docker.sock pull base

Starting a long-running worker process

# Start a very useful long-running process
JOB=$(docker run -d base /bin/sh -c "while true; do echo Hello world; sleep 1; done")

# Collect the output of the job so far
docker logs $JOB

# Kill the job
docker kill $JOB

Listing all running containers

docker ps

Expose a service on a TCP port

# Expose port 4444 of this container, and tell netcat to listen on it
JOB=$(docker run -d -p 4444 base /bin/nc -l -p 4444)

# Which public port is NATed to my container?
PORT=$(docker port $JOB 4444)

# Connect to the public port via the host's public address
# Please note that because of how routing works connecting to localhost or 127.0.0.1 $PORT will not work.
# Replace *eth0* according to your local interface name.
IP=$(ip -o -4 addr list eth0 | perl -n -e 'if (m{inet\s([\d\.]+)\/\d+\s}xms) { print $1 }')
echo hello world | nc $IP $PORT

# Verify that the network connection worked
echo "Daemon received: $(docker logs $JOB)"

Committing (saving) a container state

Save your containers state to a container image, so the state can be re-used.

When you commit your container only the differences between the image the container was created from and the current state of the container will be stored (as a diff). See which images you already have using docker images

# Commit your container to a new named image
docker commit <container_id> <some_name>

# List your containers
docker images

You now have a image state from which you can create new instances.

Read more about working_with_the_repository or continue to the complete cli

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