我在外部硬盘上创建了一个备份。然后我创建了另一个备份并将所有文件复制到另一个外部硬盘。我想检查diff是否所有内容都已复制：
user@user:/media/user$ diff -r backup backup1
Nur in backup1/home/user: file.xls.
Nur in backup1/home/user: file.zip.
（“nur”在德语中是“仅”的意思。）
差异显示两个不存在的文件：
user@user:/media/user$ file backup1/home/user/file.xls.
backup1/home/user/file.xls.: cannot open backup1/home/user/file.xls. (No such file or directory)
user@user:/media/user$ file backup1/home/user/file.zip.
backup1/home/user/file.zip.: cannot open backup1/home/user/file.zip. (No such file or directory)
diff 是如何显示这两个文件的，我该如何修复 diff 的输出？两个外部硬盘驱动器上的文件系统都是 LUKS。