Btrbck 错误：不是 BTRFS 文件系统？

Question

我使用手动分区方案安装了 Kubuntu 18.04 系统，并在安装屏幕中选择了 BTRFS。使用实用disks程序确认了这一点。

但是，当我尝试按照本教程操作时（https://github.com/ruediste/btrbck#btrbck）拍摄文件系统快照时出现此错误（请注意，我按照说明的指定顺序进行操作）：

sarah@ConvergentRefuge:~/Desktop/Desktop/Utilities/BTRFS Backups$ sudo btrbck create BackupStream
ERROR: not a btrfs filesystem: /home/sarah/Desktop/Desktop/Utilities/BTRFS Backups

磁盘：

编辑0：重试时文件夹名称没有空格，结果相同。

sarah@ConvergentRefuge:~/Desktop/Desktop/Utilities/BTRFS_Backups$ sudo btrbck create -a
Created application repository in /home/sarah/Desktop/Desktop/Utilities/BTRFS_Backups                                        
sarah@ConvergentRefuge:~/Desktop/Desktop/Utilities/BTRFS_Backups$ sudo btrbck create BackupStream                            
ERROR: not a btrfs filesystem: /home/sarah/Desktop/Desktop/Utilities/BTRFS_Backups                                           
Exception in thread "main" java.lang.RuntimeException: Error while creating sub volume in /home/sarah/Desktop/Desktop/Utilities/BTRFS_Backups/BackupStream                                                                                                
    at com.github.ruediste1.btrbck.BtrfsService.createSubVolume(BtrfsService.java:85)                                    
    at com.github.ruediste1.btrbck.StreamService.createStream(StreamService.java:134)                                    
    at com.github.ruediste1.btrbck.cli.CliMain.cmdCreate(CliMain.java:430)                                               
    at com.github.ruediste1.btrbck.cli.CliMain.processCommand(CliMain.java:141)                                          
    at com.github.ruediste1.btrbck.cli.CliMain.doMain(CliMain.java:113)                                                  
    at com.github.ruediste1.btrbck.cli.CliMain.main(CliMain.java:100)                                                    
Caused by: java.io.IOException: exit code: 1                                                                                 
    at com.github.ruediste1.btrbck.BtrfsService.createSubVolume(BtrfsService.java:54)                                    
    ... 5 more