btrfs send/receive test failing

[Sam Bull]

I'm trying out the btrfs send|receive command as shown on the
incremental backup wiki page, but the command is failing. I've tried it
with sudo as it had not permitted errors, but still no luck. The output
is:

        s@s-Air:~$ btrfs send /home/BACKUP | btrfs receive 
/media/s/99b1c51d-b3bb-4179-a621-9d5a27acc385/Air
        ERROR: failed to determine mount point for /home/BACKUP
        ERROR: failed to open destination directory 
/media/s/99b1c51d-b3bb-4179-a621-9d5a27acc385/Air. Operation not permitted
        
        s@s-Air:~$ sudo btrfs send /home/BACKUP | btrfs receive 
/media/s/99b1c51d-b3bb-4179-a621-9d5a27acc385/Air
        ERROR: failed to open destination directory 
/media/s/99b1c51d-b3bb-4179-a621-9d5a27acc385/Air. Operation not permitted
        [sudo] password for s: 
        At subvol /home/BACKUP
        ERROR: open @home/BACKUP failed. No such file or directory
        
        s@s-Air:~$ sudo btrfs send /home/BACKUP | sudo btrfs receive 
/media/s/99b1c51d-b3bb-4179-a621-9d5a27acc385/Air
        At subvol /home/BACKUP
        ERROR: open @home/BACKUP failed. No such file or directory

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