What are the pros and cons of using Named vs Anonymous volumes in Docker for self-hosting?
I’ve always used “regular” Anonymous volumes, and that’s what is usually in official docker-compose.yml
examples for various apps:
volumes:
- ./myAppDataFolder:/data
where myAppDataFolder/
is in the same folder as the docker-compose.yml file.
As a self-hoster I find this neat and tidy; my docker folder has a subfolder for each app. Each app folder has a docker-compose.yml
, .env
and one or more data-folders. I version-control the compose files, and back up the data folders.
However some apps have docker-compose.yml
examples using named volumes:
services:
mealie:
volumes:
- mealie-data:/app/data/
volumes:
mealie-data:
I had to google documentation https://docs.docker.com/engine/storage/volumes/
to find that the volume is actually called mealie_mealie-data
$ docker volume ls
DRIVER VOLUME NAME
...
local mealie_mealie-data
and it is stored in /var/lib/docker/volumes/mealie_mealie-data/_data
$ docker volume inspect mealie_mealie-data
...
"Mountpoint": "/var/lib/docker/volumes/mealie_mealie-data/_data",
...
I tried googling the why of named volumes, but most answers were talking about things that sounded very enterprise’y, docker swarms, and how all state information should be stored in “the database” so you shouldnt need to ever touch the actual files backing the volume for any container.
So to summarize: Named volumes, why? Or why not? What are your preferences? Given the context that we are self-hosting, and not running huge enterprise clusters.
Named volumes let you specify more details like the type of driver to use.
For example, say you wanted to store your data in Minio, which is like S3, rather than on the local file system. You’d make a named volume and use the s3 driver.
Plus it helps with cross-container stuff. Like if you wanted sabnzbd and sonarr and radarr to use the same directory you just need to specify it once.
Or just something as simple as using a SMB/CIFS share for your data. Instead of mounting the share before running your container, you can make Docker do it by specifying it like this:
services: my-service: ... volumes: - my-smb-share:/data:rw volumes: my-smb-share: driver_opts: type: "smb3" device: "//mynas/share" o: "rw,vers=3.1.1,addr=192.168.1.20,username=mbirth,password=supersecret,cache=loose,iocharset=utf8,noperm,hard"
For
type
you can use anything you have amount.<type>
tool available, e.g. on my Raspberry this would be:$ ls /usr/sbin/mount.* /usr/sbin/mount.cifs* /usr/sbin/mount.fuse3* /usr/sbin/mount.nilfs2* /usr/sbin/mount.ntfs-3g@ /usr/sbin/mount.ubifs* /usr/sbin/mount.fuse@ /usr/sbin/mount.lowntfs-3g@ /usr/sbin/mount.ntfs@ /usr/sbin/mount.smb3@
And the
o
parameter is everything you would put as options to the mount command (e.g. in the 4th column in/etc/fstab
). In the case of smb3, you can runmount.smb3 --help
to see a list of available options.Doing it this way, Docker will make sure the share is mounted before running the container. Also, if you move the compose file to a different host, it’ll just work if the share is reachable from that new location.
On a simpler level, it’s just an organizational thing. There are lots of other ways data from docker is consumed, and looking through a bunch of random hashes and trying to figure out what is what is insane.