Persistent volumes

Intermediate Docker

Mike Metzger

Data Engineering Consultant

What is a volume?

Volumes are an option to store data in Docker, unrelated to the container image or host filesystem
Are managed from the command line (or API)
Can share with multiple containers
Higher performance than file share / bind mounts
Exist until removed

volume mount.png

¹ Image modified from https://docs.docker.com

Managing volumes

docker volume
docker volume create <volumename>
docker volume ls or docker volume list
docker volume inspect
- Provides assorted metadata about the volume, including Name, Mountpoint, Options, and so forth
docker volume rm

Volume creation example

bash> docker volume create sqldata

sqldata

bash> docker volume ls

DRIVER    VOLUME NAME
local     2f2b7f710551e004dcdd9edf4cad31c37826b428de12f1c04ca02305d216ab00
local     14da7ff0c6eb29f644e6f9f9d59bbcf56b3699c04881dd7cbcaa9ecd6bef239c
local     150aa3c5c7aee30ffd1ec7ecf39f03989bf561536a9413ebed96ffbaa537d103
local     sqldata
...

Volume inspect example

bash> volume inspect sqldata

[
    {
        "CreatedAt": "2024-01-27T04:27:51Z",
        "Driver": "local",
        "Labels": null,
        "Mountpoint": "/var/lib/docker/volumes/sqldata/_data",
        "Name": "sqldata",
        "Options": null,
        "Scope": "local"
    }
]

Attaching volumes

Uses the -v command
- docker run -v <volumename>:<destination path>:<options>
- Volume name is name of existing volume
- Destination path is the location the volume will be mounted (such as /data)
- Options are optional comma-separated list of values such as ro for read-only.
--mount exists as with bind-mounts

$ docker run -v sqldata:/data postgres

Drivers

Methods of storing Docker volumes
Can include:
- Local filesystem (default)
- NFS (Unix filesharing)
- SMB / CIFS (Windows filesharing)

Let's practice!

Intermediate Docker