Table of contents
Docker-Volume 🟪
Docker allows you to create something called volumes. Volumes are like separate storage areas 💾 that can be accessed by containers 🗑️.
They allow you to store data, like a database🎛️, outside the container, so it doesn't get deleted when the container is deleted.
You can also mount from the same volume and create more containers having the same data.
Docker Network📶
Docker allows you to create virtual spaces called networks, where you can connect multiple containers (small packages that hold all the necessary files for a specific application to run).
This way, the containers can communicate with each other and with the host machine (the computer on which the Docker is installed).
When we run a container, it has its own storage space that is only accessible by that specific container. If we want to share that storage space with other containers, we can't do that.
💼Task : 1
Create a multi-container docker-compose file which will bring UP and bring DOWN containers in a single shot.
1️⃣Step : 1 We have compose a docker compose file
version: '3'
services:
backend:
build:
context: .
ports:
- "5000:5000"
environment:
MYSQL_HOST: mysql
MYSQL_USER: admin
MYSQL_PASSWORD: admin
MYSQL_DB: myDb
depends_on:
- mysql
mysql:
image: mysql:5.7
ports:
- "3306:3306"
environment:
MYSQL_ROOT_PASSWORD: root
MYSQL_DATABASE: myDb
MYSQL_USER: admin
MYSQL_PASSWORD: admin
volumes:
- ./message.sql:/docker-entrypoint-initdb.d/message.sql # Mount sql script into container's /docker-entrypoint-initdb.d directory to get table automatically created
- mysql-data:/var/lib/mysql # Mount the volume for MySQL data storage
volumes:
mysql-data:
2️⃣Step : 2
Use the docker-compose up command with the -d flag to start a multi-container application in detached mode.
docker-compose up -d
3️⃣Step : 3
Use the docker-compose scale command to increase or decrease the number of replicas for a specific service. You can also add replicas in deployment file for auto-scaling.
docker-compose up -d --scale backend=3
4️⃣Step : 4
Use the docker-compose ps command to view the status of all containers, and docker-compose logs to view the logs of a specific service.
docker-compose ps
docker-compose logs
5️⃣Step : 5
Use the docker-compose down command to stop and remove all containers, networks, and volumes associated with the application
docker-compose down
💼Task : 2
Learn how to use Docker Volumes and Named Volumes to share files and directories between multiple containers
docker volume ls
docker volume create test_volume
Create two or more containers that read and write data to the same volume using the docker run --mount command
# Container 1
docker run -d --name container1 --mount source=shared_data,target=/data alpine tail -f /dev/null
# Container 2
docker run -d --name container2 --mount source=shared_data,target=/data alpine tail -f /dev/null
In the above commands:
--name: Assigns a name to the container.--mount: Attaches the "shared_data" named volume to the container and mounts it at the "/data" directory.
Verify that the data is the same in all containers by using the docker exec command to run commands inside each container
# Add data from container1
docker exec container1 sh -c "echo 'Data from Container 1' > /data/test.txt"
# Verify data from container2
docker exec container2 cat /data/test.txt
Use the docker volume ls command to list all volumes and docker volume rm command to remove the volume when you're done.
docker volume ls
docker volume rm
📍Conclusion :
On this blog we have covered Docker-Volume & Docker-Network we have completed few task related to this.
Thank you for reading!
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