This is what I did anyhow…
Here my external disk is
Sling and it has the proper permissions
root:admin. Before it had
root:wheel which wasn’t allowing me to write to the disk as I did before.
To get the right permissions I used
sudo chown root:admin Sling/. I thought that this permission would only apply one time, but I ejected and re-mounted and it kept the permission.
Hopefully this helps.