Docker

Docker Products
• Docker Engine is an open source containerization technology for building and
containerizing your applications.
• Docker Desktop is an easy-to-install application for Mac or Windows environment that can
build and share containerized applications and microservices. Docker Desktop
includes Docker Engine, Docker CLI client, Docker Compose, Notary, Kubernetes,
and Credential Helper.
• Docker Compose is a tool for defining and running multi-container Docker applications.
• Docker Hub is a public registry that anyone can use.
• Docker Swarm is a cluster manager of Docker Engines.
• Docker Machine is a tool that lets you install Docker Engine on one or more virtual hosts.

Docker architecture (1/2)
• Docker Daemon (dockerd) listens for Docker API requests and manages
Docker objects.
• Docker Client (docker) is the primary way that many Docker users interact
with Docker. The docker command uses the Docker API.
• Docker Registry stores Docker images. Docker is configured to look for
images on Docker Hub by default.
• Docker Objects such as images, containers, networks, and volumes.

Docker Objects
Docker Objects Description
images An image is a read-only template with instructions for creating a Docker container.
containers A container is a runnable instance of an image. When a container is removed, any
changes to its state that are not stored in persistent storage disappear.
networks A network connects docker containers and services together.
volumes Volumes are the preferred mechanism for persisting data generated by and used by
Docker containers.

Volume Types
• Volumes are the best way to persist data in Docker.
• Bind mounts should be only used in development environments.
• tmpfs mounts are only stored in the host system’s memory.

Docker Commands
Command Description
docker image Manage images.
docker container Manage containers.
docker run Run a command in a new container.
docker exec Run a command in a running container.
docker volume Manage volumes.
docker network Manage networks.
docker logs Fetch logs of a container.

Docker Swarm
• A node is an instance of Docker Engine. We can run one or more nodes on
a single physical computer or a cloud server.
• A swarm consists of multiple Docker nodes which run in swarm mode and
act as managers and workers.
• A task is a running container which is part of a swarm service and managed
by a swarm manager, as opposed to a standalone container.

Manager Nodes
• Manager nodes handle cluster management tasks:
• Maintaining a cluster state.
• Scheduling services.
• Serving swarm mode HTTP API endpoints.
• To take advantage of swarm mode’s fault-tolerance features, we can have multiple
manager nodes to recover from the failure of a manager node without downtime.
• An N manager cluster tolerates the loss of at most (N-1)/2 managers.
• Docker recommends a maximum of seven manager nodes for a swarm.

Swarm Management Commands
Command Description
docker swarm Manage swarm mode.
docker node Manage Docker Swarm nodes.
docker service Manage Docker Swarm services.
docker stack Manage stacks of Docker Swarm services.

Docker Machine (1/2)
Docker Machine is a tool that lets you install Docker Engine on one or
more virtual hosts and manage the hosts with docker-machine commands.

Docker Machine Installation
1. Run the command below with Git Bash program.
$ if [[ ! -d "$HOME/bin" ]]; then mkdir -p "$HOME/bin"; fi
&& base=https://github.com/docker/machine/releases/download/v0.16.2
&& curl -L $base/docker-machine-Windows-x86_64.exe > "$HOME/bin/docker-machine.exe"
&& chmod +x "$HOME/bin/docker-machine.exe"
2. Check the installation by displaying the Docker Machine version.
$ docker-machine version

Create an external virtual switch. (1/3)

Create Docker hosts.
docker-machine create
--driver <driver name>
--hyperv-virtual-switch <Hyper-V external virtual switch name>
--hyperv-memory <size of memory in MB>
<machine name>
docker-machine create
--driver hyperv
--hyperv-virtual-switch "External Virtual Switch"
--hyperv-memory 768
worker1

List all Docker hosts.
$ docker-machine ls

Create a swarm.
$ docker-machine ssh <Docker hostname>
$ docker swarm init --advertise-addr <Docker manager node IP address>

Add a worker node to the swarm.

Add a manager node to the swarm.

AVAILABILITY
• Active means that the scheduler can assign tasks to the node.
• Pause means that the scheduler does not assign new tasks to the node, but
existing tasks remain running.
• Drain means that the scheduler does not assign new tasks to the node. The
scheduler shuts down any existing tasks and schedules them on an available
node.

MANAGER STATUS
• No value indicates a worker node that does not participate in swarm management.
• Leader means that the node is the primary manager node that makes all swarm
management and orchestration decisions for the swarm.
• Reachable means that the node is a manager node participating in the Raft
consensus quorum. If the leader node becomes unavailable, the node is eligible for
election as the new leader.
• Unavailable means that the node is a manager that cannot communicate with other
managers. If a manager node becomes unavailable, you should either join a new
manager node to the swarm or promote a worker node to be a manager.

Deploy a service in the swarm.
$ docker service create --name <service name> <image name> [command] [arguments…]

Scale the service in the swarm.
$ docker service scale <service name>=<number of tasks>

Delete the service running in the swarm.
$ docker service rm <service name>

Stack Deployment Example
$ docker stack deploy --compose-file <compose file path> <stack name>

Troubleshoot your network problems. (1/5)
If you face some network problems, for example, your machine state is
timeout.

These are steps that you can follow.
1. Check your machine problem with docker-machine env <machine name>
command.
2. In this example, you face a problem with your network certificates and the system
recommend that you can attempt to regenerate your network certificates.

3. In this case, I recommend that you should restart your machine(s) first with
docker-machine restart <machine name(s)> command.

4. And then regenerate your network certificates with
docker-machine regenerate-certs <machine name(s)> command.

5. Check your machine state again.

Docker

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