By default, FreeNAS/TrueNAS won't let you share a folder that's not part of its managed volumes, giving the error "The path must reside within a volume mount point"which probably means ZFS pools/datasets only.
This is probably for a good reason, and doing otherwise implies you're doing something outside the scope of the services it is meant to provide, and you could break stuff; this certainly won't be covered by support. Caveat emptor.
My use case is I have some old USB hard drives I attach to the NAS box so they can be accessed from jails like Plex, but aren't important enough to use precious redundant storage. They're mounted read-only into /mnt, via init commands, and it would be nice to be able to access them directly over the network too, but FreeNAS doesn't want to know about it.
So, onto breaking stuff. There's a way to trick it: bait and switch. It's really just user interface validation.
* Create a folder at the path you want to share
* Set up your share as you like, access the empty folder to test it works
* Delete the folder and replace it with a symlink!
* Restart the SMB service (if it won't bother others): it seems to lose the path, but on restart it shares as you'd expect! Maybe after a while it would work without restarting.
I can't vouch for permissions working as expected, especially around write, as I'm only accessing read-only volumes with read-only users in this instance. Mapping SMB users to *nix users is kind of madness anyway.
I had also tried:
* creating a symlink in my existing volume pool, but it didn't show up in the path browser for creating shares, and had the same error when I entered the path directly.
* creating a symlink into an existing share: for whatever reason it said I didn't have permissions for the share, though all the files and folders are mounted fully readable, but as a different user. It's possible there's a group permissions tweak to be made somewhere, or it may be SMB refusing to follow symlinks, especially across volumes/devices.
Update July 2022:
I used this same trick on TrueNAS 12.0 and it still worked. I now have a 10TB external USB3 drive for bulk, non-critical storage and I can copy from the share at > 100MB/s. However there are some caveats.
It's formatted as ext4 so it will work with Linux and FreeBSD, as TrueNAS still doesn't support writing to NTFS. I first tried exFAT so it would work with Windows too but TrueNAS doesn't appear to support that at all. It only supports ext2fs, and even then writing is quite slow - about 3-5MB/s.
The tricky part is that this time I want to be able to write to it too, even if only at 3MB/s - mainly just to move things around. However, I get an error:
I chose OpenMediaVault which is based on Debian, has a lot of the same monitoring that I needed, such as S.M.A.R.T and UPS. Through plugins it also support ZFS so I can mount my zpool - but eventually I will be decommissioning it and shifting to a file system pool such as mergerfs, or just SnapRAID for important files.
