How do I change the default storage directory to a different location?

[Livable8209]

Please bear in mind I'm a new user of podman, so I haven't had time to experiment.

I've spent some time looking around trying to figure out how to move to an external drive, but I haven't had any luck doing so.

I've freshly installed podman on Debian 12, and I've tried making storage.conf in /etc/containers and $HOME/.local/share/containers/storage/, neither of which have worked for me.

I used the following storage.conf for both of these attempts:

[storage]
driver="vfs"
graphroot="/mnt/extern/podman"

What i want to do is move all images and containers onto this external drive. Have I missed anything important?

(p.s, I've fully uninstalled podman from my server for now, and will instead experiment inside a vm)