How is the state saved inside a Docker container?

The default state inside a Docker container is temporary and disappears when the container is deleted, as containers are isolated and do not save changes to the image. To preserve the state, use:

• Volumes — special directories on the host that are mounted inside the container. Data in volumes is preserved regardless of the container's lifecycle.
• Bind mounts — mounting specific directories from the host into the container.

Thus, to save data (for example, a database, logs), you need to use volumes or bind mounts. Changes inside the container that are not saved in volumes will be lost after stopping or deleting the container.