The disk contains an unclean file system

Mounting an external disk you would also use with Windows 8, 10 or newer you might get an error that looks somewhat like this:

Ubuntu error
The NTFS partition is in an unsafe state
Error mounting /dev/sdXN
Exited with non-zero exit status 14
The disk contains an unclean file system
Metadata kept in Windows cache, refused to mount

From terminal

Find your device name (here referred to as sdXN)

lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL | grep -e sd

Try re-mount from the terminal:

#un-mount
sudo umount /dev/sdXN

#mount read/write
sudo mount -t ntfs-3g -o rw /dev/sdXN /media/wilbert/Data

Possible result:

The disk contains an unclean file system (0, 0). Metadata kept in Windows cache, refused to mount. Falling back to readonly mount because the NTFS partition is in an unsafe state. Please resume and shutdown Windows fully (no hibernation or fast restarting.)

Fix

The reason for this might be the Windows hibernation feature. When you shutdown Windows, the services are not stopped but instead are hibernated and pick up were they left the on the next boot. Only when you choose 'restart' everything is really stopped. Apparently there is also some fake speed to be gained by not cleanly closing your disks. If you are sure to have disabled this, note that with updates it might be turned on again without asking you.

You could disable the hibernation feature in Windows:

1. Control Panel
2. Hardware and Sound
3. Power Options
4. System Setting
5. Uncheck "Turn on fast startup"

You could clean-up the NTFS partition from within Ubuntu:

Install Linux NTFS tools:

sudo apt-get install ntfs-3g

Fix:

sudo ntfsfix /dev/sdXN