[小技巧] NFS mount 后无法 unmount 问题解决

问题：umount 时发生如下错误：

$ sudo umount /mnt/

/mnt was not found in /proc/mounts

/mnt was not found in /proc/mounts

解决：

umount 时使用 -l 命令。

$ sudo umount -l /mnt/

参考：

man umount:

       -l     Lazy unmount. Detach the filesystem from the filesystem hierarchy now, and cleanup all references to
              the filesystem as soon as it is not busy anymore.  (Requires kernel 2.4.11 or later.)