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GettingStartedDocker

Install Docker

For detailed instruction see: https://docs.docker.com/engine/installation/

TL;DR

If you are running OSX or Windows: Turn on your shared drives Settings -> Shared Drives

Container Basics

First Container

docker run -i -t busybox sh

Unable to find image 'busybox:latest' locally
latest: Pulling from library/busybox
1cae461a1479: Pull complete
Digest: sha256:c79345819a6882c31b41bc771d9a94fc52872fa651b36771fbe0c8461d7ee558
Status: Downloaded newer image for busybox:latest
/ #
  • run downloads image if doesn't exist, creates and starts the container
  • -i interactive (keep stdin open)
  • -t alocate a tty
  • busybox the name of the image
  • sh command to run

See running containers

In a new shell:

docker ps

CONTAINER ID    IMAGE        COMMAND        CREATED         STATUS           PORTS            NAMES
153a7c63af4a    busybox      "sh"           2 minutes ago   Up 2 minutes                      happy_meninsky
  • 153a7c63af4a The short id for the container
  • busybox image name
  • sh the command that the container was started with
  • happy_meninsky randomly generated names

See installed Images

List images

docker images

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
busybox             latest              c75bebcdd211        3 weeks ago         1.11 MB

The names of things

Most objects in Docker are identified by a sha256 hash.
You can refere to Images, Containers, Volumes, etc... by

  • Full hash c75bebcdd211f41b3a460c7bf82970ed6c75acaab9cd4c9a4e125b03ca113798
  • Short ID (first 12 characters) c75bebcdd211
  • Friendly Name
    • Containers:
      • Random: emotion_scientist
      • Defined: --name friendly-name
    • Images on Docker Hub:
      • user/repository:tag jgreat/cool-image:1.0.2
        • "Offical" Images don't require a user
        • Default tag is latest

Container Processes

Docker monitors the process of the command. If that process dies or is put in the background the container will stop.

Switch back to the origional shell with the running busybox container. Exit the shell with exit

/ # exit

You should be returned back to your local shell.

See stopped containers

Docker ps will by default just list running containers. Use the -a option to see all containers.

docker ps -a

CONTAINER ID    IMAGE        COMMAND        CREATED         STATUS                   PORTS            NAMES
153a7c63af4a    busybox      "sh"           2 minutes ago   Exited (0) 2 minutes ago                  happy_meninsky

Start a stopped container

docker start happy_meninsky
happy_meninsky

Existing containers that are started are put in the background. This is the same as starting a container with -d.

You can see the container running in the background with docker ps.

View console output from background containes (Logs)

Best Practice: Leave your application running in the forground and log to console.

To view the logs:

docker logs -f happy_meninsky

/ # / #
  • -f "follow" the log.

Stop a running container

Issue a stop command to the running container

docker stop happy_meninsky
happy_meninsky

Delete a Container

Use the rm command to delete a stopped container. You can delete a running container with the -f option.

docker rm happy_meninsky
happy_meninsky

Delete an Image

Delete the busybox image

docker rmi busybox:latest

Untagged: busybox:latest
Untagged: busybox@sha256:c79345819a6882c31b41bc771d9a94fc52872fa651b36771fbe0c8461d7ee558
Deleted: sha256:c75bebcdd211f41b3a460c7bf82970ed6c75acaab9cd4c9a4e125b03ca113798
Deleted: sha256:4ac76077f2c741c856a2419dfdb0804b18e48d2e1a9ce9c6a3f0605a2078caba

Networking

Lets grab an nginx web server and connect with our browser

Pull the image

You can pull an image without running it.

docker pull nginx:latest

latest: Pulling from library/nginx
ff3d52d8f55f: Pull complete
226f4ec56ba3: Pull complete
53d7dd52b97d: Pull complete
Digest: sha256:41ad9967ea448d7c2b203c699b429abe1ed5af331cd92533900c6d77490e0268
Status: Downloaded newer image for nginx:latest

Inspect the Image and Find the Exposed ports

"Exposed" port are hints to you and other docker containers about what ports the containerized process runs on. When containers are "linked" exposed port information and container IP address are passed to the linked container via Environment Variables.

Inspecting an image allows you to see information about the image including the exposed ports.

docker inspect nginx:latest

[
    {
        "Id": "sha256:958a7ae9e56979be256796dabd5845c704f784cd422734184999cf91f24c2547",
        "RepoTags": [
            "nginx:latest"
        ],
        "RepoDigests": [
            "nginx@sha256:41ad9967ea448d7c2b203c699b429abe1ed5af331cd92533900c6d77490e0268"
        ],
        "Parent": "",
        "Comment": "",
        "Created": "2017-05-30T17:10:45.958244153Z",
        "Container": "d7194c56a9009e7e69c9b0414467547357c50f0c74b94d73236d5ddb67f4975a",
        "ContainerConfig": {
            "Hostname": "77fbea4a3f5b",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "ExposedPorts": {
                "80/tcp": {}
            },
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "NGINX_VERSION=1.13.1-1~stretch",
                "NJS_VERSION=1.13.1.0.1.10-1~stretch"
            ],
            "Cmd": [
                "/bin/sh",
                "-c",
                "#(nop) ",
                "CMD [\"nginx\" \"-g\" \"daemon off;\"]"
            ],
            "ArgsEscaped": true,
            "Image": "sha256:c5ddc4e4bd79d5b5c4f2e76f2359cb00accb99bb6a545957dfd3a9708ea24b4d",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": [],
            "Labels": {},
            "StopSignal": "SIGTERM"
        },
        "DockerVersion": "17.03.1-ce",
        "Author": "NGINX Docker Maintainers \"[email protected]\"",
        "Config": {
            "Hostname": "77fbea4a3f5b",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "ExposedPorts": {
                "80/tcp": {}
            },
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "NGINX_VERSION=1.13.1-1~stretch",
                "NJS_VERSION=1.13.1.0.1.10-1~stretch"
            ],
            "Cmd": [
                "nginx",
                "-g",
                "daemon off;"
            ],
            "ArgsEscaped": true,
            "Image": "sha256:c5ddc4e4bd79d5b5c4f2e76f2359cb00accb99bb6a545957dfd3a9708ea24b4d",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": [],
            "Labels": {},
            "StopSignal": "SIGTERM"
        },
        "Architecture": "amd64",
        "Os": "linux",
        "Size": 109388645,
        "VirtualSize": 109388645,
        "GraphDriver": {
            "Name": "overlay2",
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/8d638753473f42e01d4bb65f1e3de271ae8777502c316405d49376282c154842/diff:/var/lib/docker/overlay2/bcbf43862ec169c8e4d85be2c7b971d7110a0928fbd6128d71cc61da1dc5bf1f/diff",
                "MergedDir": "/var/lib/docker/overlay2/55fddff7c7dc42b6f57efd03263bc7148e6110eef779e4250ea70fffe65d2ca8/merged",
                "UpperDir": "/var/lib/docker/overlay2/55fddff7c7dc42b6f57efd03263bc7148e6110eef779e4250ea70fffe65d2ca8/diff",
                "WorkDir": "/var/lib/docker/overlay2/55fddff7c7dc42b6f57efd03263bc7148e6110eef779e4250ea70fffe65d2ca8/work"
            }
        },
        "RootFS": {
            "Type": "layers",
            "Layers": [
                "sha256:8781ec54ba04ce83ebcdb5d0bf0b2bb643e1234a1c6c8bec65e8d4b20e58a90d",
                "sha256:7487bf0353a783b96a4c3bd1176847416d449940caa7592a0d31844ad16b3bce",
                "sha256:a552ca691e492edcae1873b2a3c43260f776cc2f4997c7de74cf367c0407a991"
            ]
        }
    }
]

We can see that nginx exposes port 80/tcp by default. Other ports may be exposed on the commad line at run options.

Publish a port

Containers have their own private network. On that network containers can connect to any ports on other containers. To connect to a container from your web browser or other local process you will need to "Publish" that port.

docker run -d -p 127.0.0.1:80:80 --name web nginx
1a3675a000a86d4a33ea6511b110095aafeeea13e69841234bb67aba2156c168
  • -d Background (daemon) the container
  • -p 127.0.0.1:80:80 [Host IP]:[Host Port]:[Container Port]
    • publish container port 80 on the local loopback 127.0.0.1 port 80
    • -p 80:80 would publish container port 80 to all IP addresses (to the world) on your host
    • -p 127.0.0.1:8080:80 would map the container port 80 to your host port 8080

Connect with your browser to http://127.0.0.1. You should see the default nginx page.

Clean Up
Remove the running container using the name we provided

docker rm -f web

Volumes

Sometimes you need to modify a container from what it provides by default. One way to do this is to share a file or directory between your host and the container.

Lets add our custom index.html file with a shared volume.

Docker requires a Fully Qualified Path when specifying your volume. Your -v option is going to vary from mine.

Windows Fully Qualified Path (forward slash, not backslash)

docker run -d -p 127.0.0.1:80:80 -v c:/Users/jgreat/git/GettingStartedDocker/nginx/html:/usr/share/nginx/html --name web nginx
  • -v c:/Users/jgreat/git/GettingStartedDocker/nginx/html:/usr/share/nginx/html
    • /localhost/file:/container/destination

Connect with your browser to http://127.0.0.1. You should see the new page.

OSX or Linux Run from inside the html directory. Use the pwd command to specify your current directory.

docker run -d -p 127.0.0.1:80:80 -v $(pwd):/usr/share/nginx/html --name web nginx

Troubleshooting

  • Did you turn on Shared Volumes in the Docker-For-... Settings?
  • Did you use the correct path?

Clean Up
Remove the running container using the name we provided

docker rm -f web

Build

Build an Image

Lets make our own image based off the nginx container and include our index.html

cd nginx

docker build -t jgreat/getting-started:latest .
  • -t jgreat/getting-started:latest the image tag including user and repo name

Run the Image

docker run -it --rm -p 127.0.0.1:80:80 jgreat/getting-started:latest
  • --rm will delete the continer after you exit.

Connect with your browser to http://127.0.0.1. You should see the new page.

Tag the Image

We can apply tags to your new docker contaner. Many tags can point to the same image.

docker tag jgreat/getting-started:latest jgreat/getting-started:0.0.1-nginx

Push the Image

Push the image up to docker hub for deployment or sharing.

Login to docker hub

docker login

If you don't specify a tag, all the tags will be pushed up.

docker push jgreat/getting-started

Local Development with Docker

A little bit out of date, but this blog goes over the basics https://blog.docker.com/2016/07/live-debugging-docker/

Docker Compose

Docker Compose is a way to specify and configure a group of services. Each service may run one or more containers.

Lets check out nodejs/docker-compose.yaml

Develop Live

Walk thorough of setting up the containers, database, volumes.

  • Sharing the code directory with the web stack
  • Environment Variables
  • .dockerignore
  • Dockerfile
  • .vscode/launch.json
  • nodemon

Start up your application stack

docker-compose up

Connect the debuger
VSCode Debuger

Modify Code
Watch nodemon pick up changes and restart.

Destroy your application stack

Stop containers, remove volumes and local images.

docker-compose down -v --rmi local

Omit the -v to keep your database volume.

More Resources and Reading

https://hub.docker.com
https://docs.docker.com/engine/userguide/eng-image/dockerfile_best-practices/
https://12factor.net/

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