Containers How To

How to install Docker (Windows Platform)

• Login to the machine using privileged account
• Download the latest Docker build from:

https://download.docker.com/win/edge/Docker%20Desktop%20Installer.exe

How to install Docker (Ubuntu)

• Login to the machine using privileged account
• Follow the instructions below:

https://docs.docker.com/install/linux/docker-ce/ubuntu/

How to install Docker (RHEL / CentOS)

• Login to the machine using privileged account
• Follow the instructions below:

https://docs.docker.com/install/linux/docker-ce/centos/

Common Docker commands

• Check the Docker version:

docker --version

• Pull and run “hello-world” image from Docker hub:

docker run hello-world

• List images:

docker images

• List all images:

docker image ls

• Pull an image from Docker hub:
• docker image pull alpine
• Remove Docker image (by image name) from the local machine:

docker image rm nginx

• List all containers:

docker container ls --all

• List active containers:

docker ps

• List all container processes (same as docker container ls command)

docker ps --all

• Pull nginx web server from Docker hub and run it on port 80 on the local machine:

docker run --detach --publish 80:80 --name webserver nginx

Note: Open browser and enter the URL http://localhost to make sure the web server is working

• Start a container in the background:

docker run -d jenkins

• Start an interactive shell command from a container (by image name):

docker run -it nginx bash

• Mount a folder from the local machine into a docker container, and map port 8080 locally to port 80 on the container (container name nginx):

docker run -v /full/path/to/html/directory:/usr/share/nginx/html:ro -p 8080:80 -d nginx

• Stop running container (by container name) from the local machine:

docker container stop webserver

• Start (a stopped) docker container (by container name) on the local machine:

docker container start webserver

• Kill all running containers:

docker kill $(docker ps -q)

• Remove all stopped containers:

docker rm $(docker ps -a -q)

• Remove container (by container name) from the local machine:

docker container rm webserver

• View logs from a running container (by container name):

docker container logs webserver

• Show live logs of running container:

docker logs -f c7337

• View top processes inside a container (by container name):

docker container top webserver

• Show exposed ports of a container:

docker port c7337

Building a Docker image

• Create a sample Dockerfile on the local machine, with the following content:

FROM nginx

COPY html /usr/share/nginx/html

• Run the command below (from the local folder containing Dockerfile and html folder) to build a custom docker image:

docker build -t mynginx .

• Build a Docker image from a Dockerfile:

docker build -f path/to/Dockerfile -t mynginx .

• Force rebuild of Docker image (from the current directory):

docker build --no-cache .

• Convert a container to image:

docker commit c7337 myimage

• Run the newly created custom docker image:

docker run --name mynginx -d -p 8080:80 mynginx

• Open a browser and check that the custom image web server is running (http://localhost:8080)

Docker file instructions

• FROM <base_image_name>:<image_version>

Purpose: Set the base image to create the container from

Example: FROM Ubuntu:15.04

• RUN <command>

Purpose: Execute commands inside the container

Example: RUN apt-get update -y

• CMD [“command”,”parameter1”,”parameter2”]

Purpose: Define a default command to run when the container starts

Example: CMD [“echo”,”Hello World!”]

• EXPOSE <port>

Purpose: Informs docker that the container listens on specific port number at runtime

Example: EXPOSE 80/tcp

• COPY <src> <dest>

Purpose: Copy files/folders from the local machine into the Docker container

Example: COPY html /www/html #Copy html folder into /www/html inside the container

• ADD <src_file> <dest>

Purpose: Copy archive file from the local machine into the docker container and extract it, or copy the content of a folder inside a URL into the docker container

Example 1: ADD myfile.tar.gz /myfolder

Example 2: ADD http://www.example.com/folder /folder

• ENV variable_name=variable_data

Purpose: Creates an environment variable inside a docker container

Reference:

https://linuxize.com/post/how-to-build-docker-images-with-dockerfile/

Common Docker commands for using Docker hub registry

• Login to the docker hub using registered account:

docker login -u <username> -p <password>

• Tag a docker image created locally:

docker tag <image-id> <username>/<repo-name>:<tag>

Example: docker tag 3fd9065eaf02 shrikantlavhate/kerneltalks

• Push a docker image from the local machine into the docker hub:

docker push <username>/<repo-name>:<tag>

Example: docker push shrikantlavhate/kerneltalks

• Pull a docker image from docker hub:

docker pull <username>/<repo-name>:<tag>

Example: docker pull alpine:latest

• Logoff docker hub:

docker logout

References

• Intro Guide to Dockerfile Best Practices

https://blog.docker.com/2019/07/intro-guide-to-dockerfile-best-practices/