我有一个无法卸载的已安装分区：
> sudo umount /dev/sdc1
umount: /home/me/mounts/sdc1: not mounted.
> sudo mount | grep sdc1
/dev/sdc1 on /home/me/mounts/sdc1 type ext4 (rw,relatime)
有什么帮助吗？
编辑：我也尝试过：
> sudo umount /home/me/mounts/sdc1
Could not unlink the key(s) from your keying. Please use `keyctl unlink` if you wish to remove the key(s). Proceeding with umount.
umount: /home/me/mounts/sdc1: not mounted.