I just created a new backup pool to backup the main pool and tried to use zfs send/recv but I get the error messages below. I generally don't have any zfs datasets, just the pools them selves populated by folders created by Mac OS Finder. However, I did create a "test" dataset in the example below thinking that was maybe required but nit didn't work. So how do you copy one pool to another on the same system?
~ xxxx$ sudo zfs send ExternalZFSPool2/test@thursday | zfs recv BackupPool
cannot receive new filesystem stream: destination 'BackupPool' exists
must specify -F to overwrite it
warning: cannot send 'ExternalZFSPool2/test@thursday': Broken pipe
~ xxxx$ sudo zfs send ExternalZFSPool2/test@thursday | zfs recv BackupPool/backuptest
cannot receive new filesystem stream: permission denied
warning: cannot send 'ExternalZFSPool2/test@thursday': Broken pipe