XXX~$ sudo umount ShareFolder
umount: ShareFolder: target is busy
方法：
umount -l /PATH/OF/BUSY-DEVICE umount -f /PATH/OF/BUSY-NFS(NETWORK-FILE-SYSTEM)
参考：
https://stackoverflow.com/questions/7878707/umount-a-busy-device
原文：https://www.cnblogs.com/dgang1989/p/9705753.html