# Day 19 Task: Docker for DevOps Engineers part-3 #Docker-Volume \-Docker volumes are **file systems mounted on Docker containers to preserve data generated by the running container**. \-The data doesn't persist when that container no longer exists, and it can be difficult to get the data out of the container if another process needs it. \-Volumes are the preferred mechanism for **persisting data generated by and used by Docker containers**. While bind mounts are dependent on the directory structure and OS of the host machine, volumes are completely managed by Docker. #Docker- Networking \-Docker networking **allows you to attach a container to as many networks as you like**. \-You can also attach an already-running container. Go ahead and attach your running web app to my\_bridge. \-There are three common Docker network types – **bridge networks, used within a single host, overlay networks, for multi-host communication, and macvlan networks** which are used to connect Docker containers directly to host network interfaces. \-Container networking **allows containers to communicate with other containers or hosts to share resources and data**. Modern container networking aims to standardize and optimize container data flows, creating zones of isolation that allow large numbers of containers to communicate efficiently and securely.

#task1

i). Create a multi-container docker-compose file that will bring UP and bring DOWN containers in a single shot

(Example - Create application and database container)

* Use the `docker-compose up` command with the `-d` flag to start a multi-container application in detached mode. ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1680675857998/72a81ef4-40f3-4501-ae1e-7770fa8a94f3.png align="center") * Use the `docker-compose scale` command to increase or decrease the number of replicas for a specific service. You can * also add [`replicas`](https://stackoverflow.com/questions/63408708/how-to-scale-from-within-docker-compose-file) in the deployment file for *auto-scaling*. ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1680676487765/edd75c1f-baea-449d-8486-6aadd156292c.png align="center") * Use the `docker-compose down` command to stop and remove all containers, networks, and volumes associated with the application. ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1680676469104/f49ea69e-12fb-4189-9b68-7a72340dd659.png align="center")

#Task-2

i). Learn how to use Docker Volumes and Named Volumes to share files and directories between multiple containers.

ii). Create two or more containers that read and write data to the same volume using the docker run --mount command.

iii). Verify that the data is the same in all containers by using the docker exec command to run commands inside each container.

iv). Use the docker volume ls command to list all volumes and the docker volume rm command to remove the volume when you're done.

i). Create a Docker volume: sudo docker volume create my\_volume ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1680676620695/3019f785-169f-4509-b0b6-ff4e6958250e.png align="center") ii). Volume inspect docker volume inspect mt\_volume ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1680688204394/c006f025-a6e1-480c-9915-f0e33b8bcd0b.png align="center") iii)Create two or more containers that read and write data to the same volume using the docker run --mount command. ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1680688715304/aa470ec4-bdeb-4732-95a5-0c190e772a1f.png align="center") iv). Verify that the data is the same in all containers by using the docker exec command to run commands inside each container. verification % docker exec -it 7708dbcd7b22 sh ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1680689433159/b3f4cf82-3d0a-4189-aa10-1eb4e055aa7f.png align="center") v). Use the docker volume ls command to list all volumes and the docker volume rm command to remove the volume when you're done. \-docker volume ls \-docker stop 7708dbc7b22 \-docker volume rm 7708dbc7b22 \-docker volume rm my\_volume ![](https://cdn.hashnode.com/res/hashnode/image/upload/v1680689667812/641ac2e2-0397-41c7-b89e-b13acca49660.png align="center")