Docker Volumes

A Docker image is a collection of read-only layers. When you launch a container from an image, Docker adds a read-write layer to the top of that stack of read-only layers. Docker calls this the Union File System.

Any time a file is changed, Docker makes a copy of the file from the read-only layers up into the top read-write layer. This leaves the original (read-only) file unchanged.

When a container is deleted, that top read-write layer is lost. This means that any changes made after the container was launched are now gone.

 A volume allows data to persist, even when a container is deleted. Volumes are also a convenient way to share data between the host and the container.

Mounting a volume is a good solution if you want to:

·       Push data to a container.

·       Pull data from a container.

·       Share data between containers.

A Docker volume "lives" outside the container, on the host machine.

From the container, the volume acts like a folder which you can use to store and retrieve data. It is simply a mount point to a directory on the host.

To create a volume, use the command:

sudo docker volume create --name [volume name]

 

List Volumes

To list all Docker volumes on the system, use the command:

sudo docker volume ls

This will return a list of all of the Docker volumes which have been created on the host.

Inspect a Volume

To inspect a named volume, use the command:

sudo docker volume inspect [volume name]

 

 Remove a Volume

To remove a named volume, use the command:

sudo docker volume rm [volume name]