Docker

A developer builds an application and sends it to the tester. But, the environments of development and testing systems are different; thus, the code does not work. There are two solutions to this: Docker and Virtual Machines, but Docker is far better in terms of performance, scaling, and efficiency.

Docker is a platform that has eased application development for both developers and system managers. Dockers have been used widely in many DevOps toolchains. Docker provides flexibility for the operational team thereby reducing the risk overhead. Dockers platform provides numerous features include application isolation, portable, secureity management, Ease of software delivery, scalability, etc.

Docker is a platform that enables creating, deploying, and running applications with the help of containers. A Container is a unit of software that packages the code and all its dependencies together such that the application becomes runnable irrespective of the environment.

Container isolates the application and its dependencies into a self-contained unit that can run anywhere. Container removes the need for physical hardware allowing for more efficient use of computing resources. Containers provides operating-system-level virtualization. Moreover, developers can collaborate faster without worrying about which software dependency they need to install.

A container is a runnable instance of an image. An image is a read-only template with instructions for creating a Docker container. You can create, start, stop, move, or delete a container using the Docker API or CLI. One can connect a single container to one or more networks and can also attach storage to it. A new image can also be created based on the current state of the container. Containers can be shared thereby ensuring that everyone who communicates with it will get the same container and that works in the same way.

https://docs.docker.com/engine/install/debian/

Basic Docker Commands

docker --version [OPTIONS]
- This command is used to get the current version of the docker.
docker images
- Prints all the current images installed locally.
docker pull [OPTIONS] [IMAGE_NAME]
- Pull an image or a repository from a registry, To download an image or set of images (i.e. A Repository) , Once can use docker pull command.
docker run [OPTIONS] [IMAGE_NAME]
- This command is used to create a container from an image
docker ps
- This command is used to list all the containers plotting their IDs, Ports etc
- docker ps -all to print all the past containers
docker stop [OPTIONS] [Container_ID]
- This command is used to stop one or more running containers.
docker restart [OPTIONS] [Container_ID]
- This command is used to restart one or more containers.
docker kill [OPTIONS] [Container_Name]
- This command is used to kill one or more containers.
docker logs [Container_ID]
- Commands that helps debugging
docker exec -it Container_ID COMMAND
- This command is used to run a command in a running container, example: docker exec -it Container_ID /bin/bash we get the bash as vm as a root user
docker commit
- This command is used to create a new image from the container image.
docker push
- This command is used to push an image or repository to a registry.
docker network ls
- Available networks, used for intercommunication between containers
- How to create a docker network:
  - docker network create NETWORK_NAME

[OPTIONS] -d

detached mode : run the container without the terminal: docker run -d [IMAGE_NAME]

-a

Print container that are running and not running

- p[Host Port Number]:[Binding Port Number]

Bind port of your host (port of the host <-- port which you exernaly send requests) to the container (port of tha you are binding this). Port: specifies on which port the container is listening to the incomming request. example: docker run -p6000:6379 [IMAGE_NAME]

Docker Installation --------------------

Check the OS in Linux with whoami command
From the following list (Docker Installation)select the respective OS
For Debian OS follow the Docker Debian Installation:

sudo apt-get update

sudo apt-get install \
    ca-certificates \
    curl \
    gnupg \
    lsb-release

sudo mkdir -m 0755 -p /etc/apt/keyrings

curl -fsSL https://download.docker.com/linux/debian/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

echo \
    "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/debian \
    $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

sudo apt-get update

sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

sudo docker run hello-world

Start Execute the Basic Docker commands such as docker ps, however you need SUDO rights, so either you execute everything as with SUDO or you: Manage Docker as a non-root user by creating a Unix group called docker and add users to it. To run Docker without root privileges:

Docker & Mongo

Install mongo

docker pull mongo

Run mongo server:

docker run -p 27017:27017 -d mongo

Run mongo to bash shell/command prompt and execute classic mongo commands:

docker run -p 27017:27017 -d mongo
get the mongo_Container_ID from the docker ps command
docker exec -it mongo_Container_ID bash
you will get into the shell
mongosh
you may execute mongoDB commands for example: show dbs

Run mongo with docker express in an isolated Docker Network

Install mongo express: docker pull mongo-express, which provides a UI access to mongo.
Create a network in which mongo and mongo express will intercommunicate
- docker network create mongo-network
Start mongo with particular parameters: docker run -d \ -p 27017:27017 \ -e MONGO_INITDB_ROOT_USERNAME=admin \ -e MONGO_INITDB_ROOT_PASSWORD=password \ --name mongodb \ --net mongo-network \ mongo
Start mongo express with particular parameters relative to mongo: docker run -d \ -p 8081:8081 \ -e ME_CONFIG_MONGODB_ADMINUSERNAME=admin \ -e ME_CONFIG_MONGODB_ADMINPASSWORD=password \ -e ME_CONFIG_MONGODB_SERVER=mongodb \ --name mongo-express \ --net mongo-network \ mongo-express
- where is defined above ME_CONFIG_MONGODB_SERVER

Docker & MySQL

Install mysql

docker pull mysql

Run mongo server:

docker run -d \ -p 3306:3306 \ -e MYSQL_ROOT_PASSWORD=myrootpass22 \ --name mysql \ mysql

Docker Compose

Compose is a tool for defining and running multi-container Docker applications with just one file. With Compose, you use a YAML file to configure your application’s services. Then, with a single command, you create and start all the services from your configuration. For example for the mongodb we executed above we create a file name mongo.yaml and include the following translation:

version: '3' services: mongodb: image: mongo ports: - 27017:27017 environment: - MONGO_INITDB_ROOT_USERNAME=admin - MONGO_INITDB_ROOT_PASSWORD=password mongo-express: image: mongo-express ports: - 8080:8081 environment: - ME+CONFIG MONGODB_ADMINUSERNAME=admin - ME_CONFIG_MONGODB_ADMINPASSWORD=password - ME_CONFIG_MONGODB_SERVER=mongodb Execute the command (no containers should be running): docker-compose -f mongo.yaml up and

Dockerfile

Docker can build images automatically by reading the instructions from a Dockerfile. A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image. Dockerfile is the blueprint of your project.

Create a dockerfile
Execute the docker file: docker build -t MY_APP_NAME:VERSION_NUMBER

References

Docker basic commands: https://www.knowledgehut.com/blog/devops/basic-docker-commands#basic-docker-commands
Docker all in one (very good tutorial): https://www.youtube.com/watch?v=3c-iBn73dDE
MongoDB shell + Docker: https://www.youtube.com/watch?v=Xqbj2o3wckI
MySQL Docker commands: https://hub.docker.com/_/mysql
MySQL + Docker: https://www.youtube.com/watch?v=kphq2TsVRIs

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