当安装手动使用NFS共享mount和形式的路径<domain/ip>:<path>/<path>或<domain/ip>:/<path>/<path>，umount未能找到在路径/proc/mounts，尽管事实上该路径实际上是在中列出/proc/mounts。
这与这个问题中的问题相同：How to solve this NFS unmunt problem?
重现步骤：
# mount --version
mount from util-linux 2.24.1 (libmount 2.24.0: debug, assert)
# mkdir mountpath
# mount 192.168.2.101:/devices mountpath
# umount mountpath
/home/.../mountpath was not found in /proc/mounts
# grep mountpath /proc/mounts
192.168.2.101://devices /home/.../mountpath nfs4 rw,[snip],addr=192.168.2.101 0 0
我怎样才能卸载这个安装？