Docker

Docker is a set of platform as a service products that uses OS-level virtualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries and configuration files; they can communicate with each other through well-defined channels.

Key

Command	Explanation
docker	Reference the Docker client.
exec	Run another command.
-it	Allow us to provide input to the container. Combination of -i (attach to standard in) and -t (attach to standard out, nicely displays output).
<container id>	ID of the container.
<command>	Command to execute.
-a	Display all results. Attach this option to the container.

Run Containers

docker run

Command	Functionality	Output
docker run <image>	Start a new container from an image. docker run = docker create + docker start	docker run nodejs
docker run -d <image>	Start a new container from an image in a detached state. You can continue to use the CLI without seeing its immediate output.	docker run -d nginx
docker run --name <container name> <image>	Assign the container a name.	docker run --name webapp nginx
docker run -p <host port>:<container port> <image>	Map the container’s ports.	docker run -p 8080:80 nginx
docker run -P <image>	Map all ports.	docker run -P nginx

docker create

Command	Functionality	Output
docker create <image name>	Creates a container from an image.	docker create nginx

docker start

Command	Functionality	Output
docker start -a <id>	Start a container.	docker start -a 7fb44b5f5e7a7fcd1320d7c01de4e32479679d594ce97416ae6d70d3810a421a

Manage Containers

docker ps

Command	Functionality	Output
docker ps	List containers.	See table below.
docker ps --all or docker ps -a	List all containers, even if they’ve been stopped or exited.	See table below.

CONTAINER ID   IMAGE                    COMMAND                  CREATED      STATUS                PORTS                  NAMES
a2506c9c4550   httpd                    "/usr/sbin/init"         4 days ago   Up 4 days             0.0.0.0:8000->80/tcp   httpd
b7ca26bf433b   mysql/mysql-server:5.5   "/entrypoint.sh mysq…"   4 days ago   Up 4 days (healthy)   3306/tcp               cw-mysql

Manage Various

Command	Functionality	Output
docker images	Display a list of all available images that have been downloaded.
docker pull <container id>	Download the container immediately without checking if it exists locally first.	docker pull nginx
docker logs <container id>	Get logs from a container.	docker logs e19f6f828ddc9254752388a474e50635db3cf4885cd7c3aa8d414d8ccd104ee6

docker exec

Command	Functionality	Output
docker exec <container> <command>	Execute a command within the image.	docker exec silly_sammet cat /etc/hosts
docker exec -it	Execute an additional command in a container.	docker exec -it 0d2ccab14d7d redis-cli or docker exec -it 0d2ccab14d7d sh

Get shell.

docker run -it busybox sh

Clean Up

Clean All

Command	Functionality
docker system prune	Cleans up dangling images, containers, volumes, and networks (ie, not associated with a container).
docker system prune -a	Additionally remove any stopped containers and all unused images (not just dangling images).

Clean Containers

Command	Functionality
docker stop <container id>	Stop a container. If it doesn’t shut down in 10 seconds it will automatically kill the container.
docker kill <container id>	Kill a container.
docker rm <container id>	Removes a container.	docker rm silly_sammet
docker container prune	Delete stopped containers.

Clean Images

Command	Functionality
docker rmi <image>	Remove the image permanently.	docker rmi nginx
docker image prune -a	Delete all the images.

Images vs. Container

An image is a package or template, similar to a VM template. It is used to create 1 or more containers.

Containers are running instances of images that are isolated and have their own environments and processes.

To Categorize

Writing a dockerfile is similar to being given a computer with no OS and being told to install Chrome.

Tag an image docker build -t mmaether/redis:latest .

copy ./ ./ Command, path to folder to copy from on your machine relative to build context, Place to copy stuff to inside the container.

Port Mapping

Common Images

Jenkins

Jenkins:

docker run -p 8080:8080 jenkins, then go to localhost:8080

Sometimes after running these commands, you may need to run docker inspect <container id> to find the IPAddress.

You may also need to download a different version to get this to work.

docker run -p 8080:8080 -v /root/my-jenkins-data:/var/jenkins_home -u root jenkins/jenkins:lts

Creating my own image

1. Install OS - Ubuntu
2. Update apt repo
3. Install dependencies using apt
4. Install Python dependencies using pip
5. Copy source code to /opt folder
6. Run the server using “flask” command

docker build Dockerfile -t mmaether/my-custom-app

docker build -t webapp-color .

docker push mmaether/my-custom-app - Add image to Docker Hub repo.

docker build . -t my-simple-webapp

docker push mmaether/my-simple-webapp: Publish to Docker Hub.