Docker Image

Docker images are built with custom dependencies of software and applications(chrome, curl, spotify), it is a combination of OS and its dependencies which is not available at docker hub.

Steps to build docker image - Write down steps to deploy manually flash application.

1. OS – Ubunutu
2. Update the source repository using apt command – update apt repo
3. Install dependencies using apt.
4. Install python dependencies using pip command.
5. Copy source code to /opt folder.
6. Run the web server using ‘flash’ command.

Docker file

Docker file is a file which we can specify the instruction and its argument to build a image. Some of the instructions are RUN, COPY, ENTRYPOINT, CMD.

Docker file for flash application

>> From Ubuntu
>>Run apt-get update
>>RUN apt-get install python
>>RUN pip install flask
>>RUN pip install flask-mysql
>>COPY . /opt/source-code
>>ENTRYPOINT FLASK_APP=/opt/source-code/app.py flask run

Docker Image build command

docker build Dockerfile -t image_name Above command build docker image as mentioned in Dockerfile and name it as docker image name mentioned.

Docker push Command

docker push image_name command will push the docker image in to the docker hub.

Docker Layered Architecture

Docker builds images in laa yered architecture. So when a command fails the previous successful image built is cached and when we try to rebuild the image, It starts from the last successful layer.

Docker History

It allows to view the size of the image and its information.

docker history image_name command helps to view the history of the image name with its size and details.

Command to check the linux flaour - cat /etc/*-release

Docker Setting Environment Variables:

Docker environment variables can be passed through -e argument when running a container.

docker run -e APP_COLOR=blue image_name

docker inspect container_name – will list the container name with all config and environment variable which is present inside the configuration.

Docker command to start mysql and name and pass the env variables.

docker run -d –name mysql-db -e MYSQL_ROOT_PASSWORD=db_pass123 mysql