How to ensure persistent Docker storage using data volumes
Docker containers are aimed at creating and managing application environments that can be deployed in the matter of a few seconds. Containers are usually created for temporary purposes, depending on its business application.
When a container’s application purpose is served, it can be deleted and the resources allotted to it can be reused for creating new containers for other purposes, especially when used in development and testing services.
Why do you need persistent Docker storage?
The default Docker storage is not persistent in nature, which means that the data in the container would be lost upon a crash or deletion of the container.
Many online businesses that use Docker infrastructure may require persistent data for their containers, such as in the case of an application that stores data in the database for future use.
To share data among the Docker containers and to ensure that the data is secure and safe even after a container rebuild, you need to configure persistent data storage in your system.
There are some workarounds for ensuring persistent docker storage, such as data volumes, data volume containers or plugins. Today, we’ll discuss how data volumes can be used with Docker containers to store data in a persistent manner.
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Using data volumes for persistent Docker storage
In Docker, persistent storage can be achieved with the help of data volumes. Data volume is a directory in the Docker machine, which can store container data.
Once the data volumes are created, they can be shared among containers. The data stored in these data volumes persist even after deleting the container, and so can be used for purposes such as coding.
The default data volume directory is ‘/var/lib/docker/volumes’. This directory would contain the volumes specific to each container and they are identified using volume IDs – 64-bit randomly generated numbers.
Create data volumes for docker storage
To use data volumes, the volume has to be created first. To create a data volume, use the command:
docker volume create <data-volume> -o size=100GB
This command will create a data-volume with size 100GB in the host machine.
Once the data volume is created, we can create containers with this data volume associated to them. The data volume name can be given as parameter while creating containers using the Dockerfile or with ‘-v’ flag in ‘docker run’ command:
docker run -d -P --name web -v /data-volume nginx
When a container is created, a data volume would be associated with it in the folder ‘/data-volume’. By specifying the data volume name during container creation, it is possible to share data among containers.
To ensure that data corruption does not occur due to simultaneous access to the data by multiple applications in different Docker containers, care has to be exercised in managing the application ‘writes’.
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