Docker 101 workshop

This is complementary slides of Hands on session for Docker 101 Workshop

Transcript

1. Docker Workshop #1 Kunal Kushwaha
2. Docker Vocabulary Docker Image The basis of a Docker container. Represents a full application Docker Container The standard unit in which the application service resides and executes Docker Engine Creates, ships and runs Docker containers deployable on a physical or virtual, host locally, in a datacenter or cloud service provider
 Registry Service (Docker Hub or Docker Trusted Registry) Cloud or server based storage and distribution service for your images
3. Docker Architecture
4. Basic docker commands $ docker pull <image-name>:<tag> $ docker images 
 
 
 $ docker run –d –p 5000:80 –-name <container-name> <image-name>:<tag> $ docker ps 
 
 $ docker stop <container-name> (or <container id>) $ docker start <container-name> (or <container id>) $ docker exec <container-name> (or <container id>) [Command] 
 $ docker rm <container-name> (or <container id>) 
 $ docker rmi <image-name>:<tag> (or <image id>)

5. Docker Image Kernel Ubuntu Linux Install Python and Pip Upgrade Pip Copy Requirements Install Requirements …
6. Docker File System • Logical file system by grouping different file system primitives into branches (directories, file systems, subvolumes, snapshots) • Each branch represents a layer in a Docker image • Allows images to be constructed / deconstructed as needed vs. a huge monolithic image (ala traditional virtual machines) • When a container is started a writeable layer is added to the “top” of the file system
7. Image to Container $ docker run ubuntu:15.04
8. Sharing Image.
9. Container Layer CAS
10. Committing changes to image $ docker commit [-m “Message”] <container-id|name> <image-name>:<tag>
11. Copy on Write Super efficient: •Sub second instantiation times for containers •New container can take <1 Mb of space Containers appears to be a copy of the original image But, it is really just a link to the original shared image If someone writes a change to the file system, a copy of the affected file/directory is “copied up” •But copy happens for only first time, when file is written.
12. Dockerfile
13. Dockerfile Overview • Script, composed of various commands and arguments listed successively. • Docker daemon on build command, automatically perform actions on a base image in order to create a new one. • Always begin with defining an image FROM which the build process starts. • Followed by commands with arguments, to perform various actions. • Has syntax, which docker daemon understands, and it uses it for interpreting the actions.
14. Dockerfile Format. # Line blocks used for commenting command argument argument .. e.g # Print "Hello docker!" RUN echo "Hello docker!"
15. Dockerfile Commands
16. FROM • It defines the base image to use to start the build process. • If a FROM image is not found on the host, docker will try to find it (and download) from the docker image index. • It needs to be the first command declared inside a Dockerfile. # Usage: FROM [image name] FROM ubuntu
17. ENV • The ENV command is used to set the environment variables (one or more). • These variables consist of “key = value” pairs, which can be accessed within the container by scripts and applications alike. # Usage: ENV key value ENV HTTP_PROXY "http://example.com:8080" ENV SERVER_WORKS 4
18. RUN • It takes a command as its argument and runs it to form the image. • It form another layer on top of the previous one which is committed. # Usage: RUN [command] RUN apt-get install -y httpd RUN mkdir -p /opt/myapp RUN echo "version=1" > /opt/myapp/myapp.config
19. ADD • The ADD command gets two arguments: a source and a destination. • Copies the files from source on host into destination in container filesystem. • If Source is URL, contents are downloaded and placed at destination. # Usage: ADD [source directory or URL] [destination directory] ADD /my_app_folder /my_app_folder
20. VOLUME • Enables access from your container to a directory on the host machine (i.e. mounting it). # Usage: VOLUME ["/dir_1", "/dir_2" ..] VOLUME ["/data"]
21. EXPOSE • Associate a specified port to enable networking between the running process inside the container and the outside world (i.e. the host). # Usage: EXPOSE [port] EXPOSE 8080
22. WORKDIR • Sets where the command defined with CMD is to be executed • Also, this folder will be your working directory if you enter container by docker exec # Usage: WORKDIR /path WORKDIR ~/
23. CMD • Similar to RUN, can be used for executing a specific command. • But, unlike RUN it is not executed while image is build. • So used for specifying default initial command on container creation. • Command specified in CMD command should already be present in Image. • Overridden by command specified in docker run # Usage 1: CMD application "argument", "argument", .. CMD “echo” "Hello docker!” # Usage 2: CMD [“application”, "argument", "argument", ..] CMD [“echo”, "Hello docker!”]
24. ENTRYPOINT • Sets the concrete default application that is used every time a container is created using the image. • Couple with CMD, can remove "application" from CMD and just leave "arguments" which will be passed to the ENTRYPOINT. • Helps in arguments to be overridden at container creation. # Usage: ENTRYPOINT application "argument", "argument", .. ENTRYPOINT echo # Usage example with CMD: # Arguments set with CMD can be overridden during *run* CMD "Hello docker!" ENTRYPOINT echo
25. Building Image # docker build -t <image-name>:<tag> . docker build -t kunalkushwaha/my-demo-app .
27. Build your first Image. • Image that echo “Hello World” • Expected output $ ls Dockerfile $ docker build -t first-image . $ docker images $ docker run first-image Hello World
28. Lets add little more • Image that can only echo • Default output should be “How can I help you?” • Otherwise output argument passed while container is created. • Expected output $ ls Dockerfile $ docker build -t first-image:v1 . $ docker images $ docker run first-image:v1 How can I help you? $ docker run first-image:v1 Bingo!! Bingo!!
29. How about running web server? • Take base image as ubuntu. • install nginx • Create container to test if image have nginx running. • Expected output $ ls Dockerfile $ docker build -t nginx-image:v1 . $ docker images $ docker run nginx-image:v1 How can I help you? $ docker run -itd -p 5000:80 nginx-image:v1 $ curl localhost:5000
30. Docker hub
31. Docker hub Docker Hub is a cloud-based registry service Centralized resource for container image discovery & distribution
32. Search image on docker hub. • You can find public repositories and images from Docker Hub in two ways. • “Search” from the Docker Hub website. • Use CLI docker search <image-name> • Docker Hub contains a number of Official Repositories. • These are public, certified repositories from vendors and contributors to Docker. • From vendors like Canonical, Oracle, and Red Hat that you can use as the basis to building your applications and services.
33. Docker registry commands $ docker pull $ docker search 
 
 
 $ docker login $ docker push # Retag your Image & Push $ docker tag first-image <username>/first-image $ docker login $ docker push <username>/first-image
34. So What we learnt today? • Linux containers • Docker - architecture. • docker images • docker containers • dockerfile • docker hub
35. Thank You