Docker Engine is a client-server application with these major components:
- A server which is a type of long-running program called a daemon process (the
dockerd command).The Docker daemon (dockerd) listens for Docker API requests and manages Docker objects such as images, containers, networks, and volumes. A daemon can also communicate with other daemons to manage Docker services.
- A REST API which specifies interfaces that programs can use to talk to the daemon and instruct it what to do.
- A command line interface (CLI) client (the
docker command).The Docker client (docker) is the primary way that many Docker users interact with Docker. When you use commands such as docker run, the client sends these commands to dockerd, which carries them out. The docker command uses the Docker API. The Docker client can communicate with more than one daemon.
The CLI uses the Docker REST API to control or interact with the Docker daemon through scripting or direct CLI commands. Many other Docker applications use the underlying API and CLI.The daemon creates and manages Docker objects, such as images, containers, networks, and volumes.
Docker registries
A Docker registry stores Docker images. Docker Hub is a public registry that anyone can use, and Docker is configured to look for images on Docker Hub by default. You can even run your own private registry. If you use Docker Datacenter (DDC), it includes Docker Trusted Registry (DTR).
When you use the docker pull or docker run commands, the required images are pulled from your configured registry. When you use the docker push command, your image is pushed to your configured registry.
Docker objects
When you use Docker, you are creating and using images, containers, networks, volumes, plugins, and other objects. This section is a brief overview of some of those objects.
IMAGES
An image is a read-only template with instructions for creating a Docker container. Often, an image is based on another image, with some additional customization. For example, you may build an image which is based on the ubuntu image, but installs the Apache web server and your application, as well as the configuration details needed to make your application run.
You might create your own images or you might only use those created by others and published in a registry. To build your own image, you create a Dockerfile with a simple syntax for defining the steps needed to create the image and run it. Each instruction in a Dockerfile creates a layer in the image. When you change the Dockerfile and rebuild the image, only those layers which have changed are rebuilt. This is part of what makes images so lightweight, small, and fast, when compared to other virtualization technologies.
CONTAINERS
A container is a runnable instance of an image. You can create, start, stop, move, or delete a container using the Docker API or CLI. You can connect a container to one or more networks, attach storage to it, or even create a new image based on its current state.
By default, a container is relatively well isolated from other containers and its host machine. You can control how isolated a container’s network, storage, or other underlying subsystems are from other containers or from the host machine.
A container is defined by its image as well as any configuration options you provide to it when you create or start it. When a container is removed, any changes to its state that are not stored in persistent storage disappear.
SERVICES
Services allow you to scale containers across multiple Docker daemons, which all work together as a swarm with multiple managersand workers. Each member of a swarm is a Docker daemon, and the daemons all communicate using the Docker API. A service allows you to define the desired state, such as the number of replicas of the service that must be available at any given time. By default, the service is load-balanced across all worker nodes. To the consumer, the Docker service appears to be a single application. Docker Engine supports swarm mode in Docker 1.12 and higher.
## List Docker CLI commands
docker
docker container --help
## Display Docker version and info
docker --version
docker version
docker info
## Execute Docker image
docker run hello-world
## List Docker images
docker image ls
## List Docker containers (running, all, all in quiet mode)
docker container ls
docker container ls --all
docker container ls -aq
docker build -t friendlyhello . # Create image using this directory's Dockerfile
docker run -p 4000:80 friendlyhello # Run "friendlyhello" mapping port 4000 to 80
docker run -d -p 4000:80 friendlyhello # Same thing, but in detached mode
docker container ls # List all running containers
docker container ls -a # List all containers, even those not running
docker container stop <hash> # Gracefully stop the specified container
docker container kill <hash> # Force shutdown of the specified container
docker container rm <hash> # Remove specified container from this machine
docker container rm $(docker container ls -a -q) # Remove all containers
docker image ls -a # List all images on this machine
docker image rm <image id> # Remove specified image from this machine
docker image rm $(docker image ls -a -q) # Remove all images from this machine
docker login # Log in this CLI session using your Docker credentials
docker tag <image> username/repository:tag # Tag <image> for upload to registry
docker push username/repository:tag # Upload tagged image to registry
docker run username/repository:tag # Run image from a registry
docker stack ls # List stacks or apps
docker stack deploy -c <composefile> <appname> # Run the specified Compose file
docker service ls # List running services associated with an app
docker service ps <service> # List tasks associated with an app
docker inspect <task or container> # Inspect task or container
docker container ls -q # List container IDs
docker stack rm <appname> # Tear down an application
docker swarm leave --force # Take down a single node swarm from the managerdocker-machine create --driver virtualbox myvm1 # Create a VM (Mac, Win7, Linux)
docker-machine create -d hyperv --hyperv-virtual-switch "myswitch" myvm1 # Win10
docker-machine env myvm1 # View basic information about your node
docker-machine ssh myvm1 "docker node ls" # List the nodes in your swarm
docker-machine ssh myvm1 "docker node inspect <node ID>" # Inspect a node
docker-machine ssh myvm1 "docker swarm join-token -q worker" # View join token
docker-machine ssh myvm1 # Open an SSH session with the VM; type "exit" to end
docker node ls # View nodes in swarm (while logged on to manager)
docker-machine ssh myvm2 "docker swarm leave" # Make the worker leave the swarm
docker-machine ssh myvm1 "docker swarm leave -f" # Make master leave, kill swarm
docker-machine ls # list VMs, asterisk shows which VM this shell is talking to
docker-machine start myvm1 # Start a VM that is currently not running
docker-machine env myvm1 # show environment variables and command for myvm1
eval $(docker-machine env myvm1) # Mac command to connect shell to myvm1
& "C:\Program Files\Docker\Docker\Resources\bin\docker-machine.exe" env myvm1 | Invoke-Expression # Windows command to connect shell to myvm1
docker stack deploy -c <file> <app> # Deploy an app; command shell must be set to talk to manager (myvm1), uses local Compose file
docker-machine scp docker-compose.yml myvm1:~ # Copy file to node's home dir (only required if you use ssh to connect to manager and deploy the app)
docker-machine ssh myvm1 "docker stack deploy -c <file> <app>" # Deploy an app using ssh (you must have first copied the Compose file to myvm1)
eval $(docker-machine env -u) # Disconnect shell from VMs, use native docker
docker-machine stop $(docker-machine ls -q) # Stop all running VMs
docker-machine rm $(docker-machine ls -q) # Delete all VMs and their disk images
