Docker App Development & Command Practice

What is Docker?

A platform for building,running and shipping applications. in a consistent manner so if your application works on your development machine it can run and function the same way on other machine.

Container: An isolated environment for running an application.

Container states – A container can be in one of four states: created,running, paused, exited, restarting.

Docker Image:

Docker images are The blueprints of our application which form the basis of containers. We use docker pull command to download an image.

• A standalone, executable package that can be run in a container.

• A Docker image is a binary that includes all of the requirements for running a single Docker container, as well as metadata describing its needs and capabilities.

• An image includes everything that is needed to run an application, including the application's executable code, any software on which the application depends, and any required configuration settings. You can build your own images (using a Dockerfile) or use images that have been built by others and then made available in a registry (such as Docker Hub).

• To build an image from a Dockerfile you use the docker build command.

• To run an image in a container you use the docker run command.

Containers - Created from Docker images and run the actual application. After downloading the image We create a container using docker run command. A list of running containers can be seen using the docker ps command.

Dockerfile:

A text document containing the commands to build a Docker image.
To build an image from a Dockerfile you use the docker build command.

Example Dockerfile

    #comments
    FROM golang:alpine
    ENV GO111MODULE=on
    ENV BG_COLOR=skyblue
    WORKDIR /opt/webapp
    COPY . .
    RUN go build
    RUN go install -v ./...
    EXPOSE 8180
    CMD ["dockerapp"]

We use docker build command to create container from above dockerfile

Syntax: docker build
docker build . repository=, tage=
docker build . -t mateors/hello repository=mateors/hello, tag=latest
docker build . -t mateors/hello:1 repository=mateors/hello, tag=1
docker build -f Dockerfile.dev -t helloWorld repository=helloWorld, tag=latest
docker build -f Dockerfile.dev -t helloWorld:1 repository=helloWorld, tag=1

List Images

there are two commands to show the image list

• docker images
• docker image ls

docker images --help
docker images
docker image ls

Image Build history (Show the history of an image)

docker history <imageName or ID>
docker image history <imageName or ID>

Remove ALL unused images

docker image prune

Remove one or more unused images

docker image rm <imageName or ID>
docker image remove <imageName or ID>
docker image rmi <imageName or ID>
docker image rmi -f <imageName or ID>
docker image rmi <imageName or ID> <imageName or ID> <imageName or ID>

Check build history (Show the history of an image)

docker history --help
docker history <imageName or ID>

Inspect - Display detailed information on one or more images

docker image inspect --help
docker image inspect <imageName or ID>

Tag - Tagging Images

• latest tag is just a label
• latest tag does not neccessarily mean it is the latest version of the image
• latest tag does not neccessarily reference the latest image
• Explicit tag to indentify what version you are running (docker image tag <imageID> webapp:latest)

docker build -t webapp . clean build
docker images to display all of our images
docker image tag

How can we tag an image?

There are tow ways

• One way is tag an image while building it (docker build -t webapp:2 .)
• the other way after the build (docker image tag webapp:latest webapp:1)

docker image tag <imageID> webapp:latest updates tag after build (Explicitly)

Remove a tag

Explicitely update a tagcls

How do we remove tag?

docker image remove webapp:2

docker push - Sharing Images

Login to hub.docker.com (if not registered yet please signup)

Navigate to https://hub.docker.com/repositories\

Create a Repository like github

Repo confirmation window

For publishing to docker hub tag
Syntax: docker image tag <imageName or ID> RepoPath:TAG
docker image tag 8d92 mateors/webapp:2

Now login from the command line using docker login command docker login or
winpty docker login from gitbash terminal

docker push mateors/webapp:2

Now navigate to docker repo url and refresh the page

Docker Build & Push

docker build -t webapp:beta .
docker image tag webapp:beta mateors/webapp:beta
docker push mateors/webapp:beta

Now go to the docker hub and refresh the repo page

All possible commands are listed in the following google docs

References

• Our Docker Image Location

• Docker docs