Docker containers are easiest to use with stateless applications because their filesystems are ephemeral in nature. Changes made to a container’s environment are lost when the container stops, crashes, or gets replaced.
You can Dockerize stateful applications such as databases and file servers by attaching volumes to your containers. Volumes provide persistent storage that’s independent of individual containers. You can reattach volumes to a different container after a failure or use them to share data between several containers simultaneously.
In this article, you’ll learn what volumes are and the use cases they enable. We’ll also cover some practical examples of using volumes with Docker and Docker Compose.
What Are Docker Volumes?
Volumes are a mechanism for storing data outside containers. All volumes are managed by Docker and stored in a dedicated directory on your host, usually /var/lib/docker/volumes for Linux systems.
Volumes are mounted to filesystem paths in your containers. When containers write to a path beneath a volume mount point, the changes will be applied to the volume instead of the container’s writable image layer. The written data will still be available if the container stops – as the volume’s stored separately on your host, it can be remounted to another container or accessed directly using manual tools.
Volumes work with both Linux and Windows containers. Several different drivers are available to store volume data in different services. Local storage on your Docker host is the default, but NFS volumes, CIFS/Samba shares, and device-level block storage adapters are available as alternatives. Third-party plugins can add extra storage options too.
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