this post was submitted on 01 Feb 2025
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Why use Named volume vs Anonymous volume in Docker? (reddthat.com)
submitted 22 hours ago by [email protected] to c/selfhosted
22 comments fedilink hide all child comments
 

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.

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[–] Semi_Hemi_Demigod 26 points 21 hours ago (3 children)

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.

[–] [email protected] 1 points 3 hours ago

That makes sense. I've only ever used local storage on the docker-VM, but for sure it can make sense for using external storage

[–] [email protected] 19 points 21 hours ago (4 children)

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 a mount.<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 run mount.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.

[–] [email protected] 1 points 3 hours ago

Wow thanks for this! Reading the official docker documentation I somehow missed this. Using regular well documented linux mount. tools and options will be so much better than looking for docker-specific documentation for every single type.

And knowing the docker container won't start unless the mount is available solves so much.
Does the container stop or freeze if the mount becomes unavailable? For example if the smb share host goes offline?

[–] theRealBassist 4 points 19 hours ago

Ok I did not know about this at all. I've been just mounting it on the host which has been a bit of a pain at times.

I just did a massive refactor of my stacks, but now I might have to revisit them to do this.

[–] [email protected] 2 points 17 hours ago

There's also an NFSv4 driver which is great when you're running TrueNAS

[–] [email protected] 1 points 18 hours ago

what?? im definetly using this thanks for makong me aware of it.

[–] just_another_person 5 points 21 hours ago

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.