Intro to Docker
Unit 2: Container Images
Unit 2 - Container Images : Agenda
● Define what an Image is ● Docker HUB ● Image Cache ● Tagging ● Docker File ○ Building ○ Extending
Unit 2 - Container Images : Overview
● All about images, the building blocks of containers ● What's in an image (and what isn't) ● Using Docker Hub registry ● Managing our local image cache ● Building our own images
What’s an Image?
● Application binaries and dependencies ● Metadata about the image data and how to run the image ● Not a complete OS. No Kernel... the host provides the Kernal ● Small as one file (your application binary) like in golang ● Or something like Ubuntu
Docker Hub
● Basics of Docker Hub (hub.docker.com) ○ Github for docker images ○ Create an account on hub.docker.com ● Find official and other good public images ○ Official images are the only ones without forward slashes on them ● Download images and basics of image tags
Union file system
● Unionfs is a filesystem service for Linux, FreeBSD and NetBSD which implements a union mount for other file systems. ● It allows files and directories of separate file systems, known as branches, to be transparently overlaid, forming a single coherent file system. ● Contents of directories which have the same path within the merged branches will be seen together in a single merged directory, within the new, virtual filesystem.
Docker Images and Layers
● Image layers ● Union file system ● History and inspect commands ● Copy on write ○ How containers run as expansions on top of images
Creating and Storing Container Images
● Run : docker image ls ● Run : docker history nginx:latest ○ This is not a history of what’s in the container ○ This is a history of the image changes over time ○ Every Image starts off as a basic layer called a scratch file ● Run : docker history mysql ○ Look at the difference ● Some points ○ Every layer gets its own unique sha ○ Docker uses this to check to see what changes are between each version
Docker inspect
● Run : docker image inspect nginx ○ This will show you all the default commands in the image ○ Remember most of these can be changed after the fact
Container Images
● Images are made up of file system changes and metadata ● Each layer is uniquely identified and only stored once on a host ● This saves storage space on hos and transfer time on push/pull ● A container is just a single read/write layer on top of image ● docker image history and inspect command
Image Tagging and Pushing to docker hub
● Run : docker image tag --help ● Run : docker image ls ○ Images don’t have a name ■ They have an ID and a Tag ■ They exist inside of a repository and are listed by their Tag and Image ● Tags are a pointer to an specific image commit ○ Let’s navigate to docker hub and look at images and how they are tagged ● Run : docker pull nginx:mainline ● Run : docker image ls
Image Tagging and Pushing to docker hub
● Run : docker image tag --help ● Run : docker image ls ○ Images don’t have a name ■ They have an ID and a Tag ■ They exist inside of a repository and are listed by their Tag and Image ● Tags are a pointer to an specific image commit ○ Let’s navigate to docker hub and look at images and how they are tagged ● Run : docker pull nginx:mainline ● Run : docker image ls
Tagging images
● docker image tag SOURCE_IMAGE[:TAG] TARGET_IMAGE[:TAG]
● Run : docker image tag nginx
Retagging Images
● Run : docker image tag
Dockerfile
● Navigate to the dockerfile-sample-1 in the git repo ● Open up the file ‘Dockerfile’ and review it ● Run : docker image build -t localimage . ● Run : docker image ls ● Let’s make a update and the expose port 8080 to the Dockerfile ● Rebuild the file ○ Notice the Using cache tag line in the build process ○ Its critically important the ordering of your flies ■ Keep the things you change the least at the top
Copying files to build
● Run: docker container run -p 80:80 --rm nginx ● Open up browser and webhost ● Run : docker image build -t nginx-with-html . ● Navigate to browser
Push to docker hub
● Let’s retag and send to docker hub
● Run :docker image tag nginx-with-html:latest
Lab : Build your Own Image
● Take existing Node.js app and Dockerize it ● Make Dockerfile. ○ Build it ○ Test it ○ Push it ○ Run it ● Expect this to be iterative. You seldom get it right the first time ● Details in dockerfile-assignment-1/Dockerfile ● Use the Alpine version of the official ‘node’ 6x image ● Expected result is the web site at http://localhost ● Remove from local cache, run again from Hub
Unit 2: Container Images
Docker HUB
Docker Hub To access Docker HUB, browse to: hub.docker.com (ie, nginx official) Official images, advantages, versions etc.
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Commands: ● docker search ● docker pull ● docker login ● docker push Download images: hub.docker.com (ie, nginx official)
docker search docker search [OPTIONS] TERM
docker pull docker pull [OPTIONS] NAME[:TAG|@DIGEST]
docker login docker login [OPTIONS] [SERVER]
docker push docker push [OPTIONS] NAME[:TAG]
Image Cache docker image ls docker pull nginx docker pull nginx:1.11.9 (when testing, specify the version) docker history nginx:latest docker image inspect nginx
Unit 2: Container Images
Tagging
Tagging
Tagging
Unit 2: Container Images
Docker File
Docker File
- A recipe for creating your image
File’s name is alway “Dockerfile”, contains the recipe for building the image. docker image build -t
. (“.” if called from inside the directory that contains the desired Dockerfile) Tips: things that change the least at top of file, things that change the most towards the bottom
Docker File: Build
Building:
“FROM