Manage data in Docker

By default all files created inside a container are stored on a writable container layer. This means that:

• 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.
• A container’s writable layer is tightly coupled to the host machine where the container is running. You can’t easily move the data somewhere else.
• Writing into a container’s writable layer requires a storage driver to manage the filesystem. The storage driver provides a union filesystem, using the Linux kernel. This extra abstraction reduces performance as compared to using data volumes, which write directly to the host filesystem.

Docker has two options for containers to store files on the host machine, so that the files are persisted even after the container stops: volumes, and bind mounts.

Docker also supports containers storing files in-memory on the host machine. Such files are not persisted. If you’re running Docker on Linux, tmpfs mount is used to store files in the host's system memory. If you're running Docker on Windows, named pipe is used to store files in the host's system memory.

👉 Choose the right type of mount