Fail to mount a partition

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http://unix.stackexchange.com – I successfully unmounted a partition. But I failed to mount it again. I wonder what is going wrong? $ sudo umount /windows-d $ sudo mount -t ntfs /dev/sda2 /windows-d Mount is denied because the NTFS volume is already exclusively opened. The volume may be already mounted, or another software may use it which could be identified for example by the help of the 'fuser' command. Thanks! (HowTos)