Getting Started with Docker – A Beginner's Guide:

What is Docker ?

Docker is a set of platform as a service products that use OS-level virtualization to deliver software in packages called containers. The service has both free and premium tiers. The software that hosts the containers is called Docker Engine.

Why Docker ?

• Consistency: Docker containers encapsulate an application and its dependencies, ensuring that it runs consistently across different environments.

• Efficiency: Containers are lightweight, sharing the host system’s OS kernel, which means they use fewer resources than traditional virtual machines.

• Scalability: Docker makes it easy to scale your application horizontally by running multiple container instances.

• Portability: A Docker container can run on any system that supports Docker, making it highly portable.

Essential Docker commands and RUN a mysql container :

To debug the following issue:

Step 1: Add user in docker group docker sudo usermod -aG docker $USER

Step2: Change the permissions sudo chmod 757 /var/run/docker.sock

docker pull hello-world : It will pull the hell-world image from docker hub

docker images : will display the pulled images

docker ps : will display running containers

Pull the mysql image:- Compiled version of file
docker pull mysql

RUN the command docker run -d -p 80:80 nginx:latest

It will pull and run the ngnix image
-d: It will run in background
-p: Use to publish and bind the port
80:80 Your system port( can modifiy ) : Container port
Open 80 port in firewall.
Hit the system ip address serve with 80 port.
Nginx is working

RUN the docker run hello-world:latest

RUN the docker run mysql:latest

docker run -d command will RUN your containers in Background

Mysql is asking to pass the environment variables

docker run -e MYSQL_ROOT_PASSWORD=****** mysql:latest
* denotes the passwd

Mysql container is up and running...

To Get into Mysql container RUN it in detached mode using -d :
Now its running in detached mode or running in backend.
Now you are inside the mysql container

docker system prune

This command will remove all running containers forcefully.

--> docker build -t image-name:tag path to file
This is the command used to build a Docker image.
--> docker exec -it cont_ID bash
This command is used to go inside the container.
exec: execute
-it: iterative terminal

--> docker logs cont_ID

Here's an overview of what you can expect:

1. Application output

2. Startup messages

3. Error messages

4. Access logs

5. System messages

6. Custom logging

7. Timestamps

--> docker inspect cont_ID
The output is in Key=Value format and includes a wide range of information, such as:

• ID: The unique identifier of the container.

• Image: The image from which the container was created.

• State: The current state of the container (e.g. running, exited).

• Config: Configuration options like environment variables, command to run, exposed ports, etc.

• NetworkSettings: Information about the container's networking configuration, including IP address, ports, etc.

The docker inspect command is a powerful tool for troubleshooting, auditing, and understanding the detailed configuration and state of Docker objects.

To kill a running Docker container, you have a few options. Here's a step-by-step process:

List running containers using docker ps command

Kill the container using docker kill cont_ID or cont_name command

Alternative: Stop the container gracefully using docker stop cont_ID
which will send a SIGTERM signal.

Remove the container using docker rm cont_ID command

If you want to stop and remove a container in one command then use docker rm -f cont_ID

If you remove all the stop conatiner the use docker container prune

To kill all the unused containers in one command

docker system prune

Remember:

• docker kill is immediate and doesn't allow for graceful shutdown.

• docker stop is generally preferred as it allows the application to shut down cleanly.

• Always be cautious when killing containers, especially in production environments.

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