Unable to eject/safely unmount USB drive

Question

So I'm trying to safely remove this USB drive, because when I don't it does not work properly. When I go on Nautilus and try to eject it, I get this error message:

Error ejecting: eject exited with exit code 1: eject: unable to eject, last error: Invalid argument

And when I try to safely remove it via Nautilus or Disk Utility:

Error detaching: helper exited with exit code 1: Detaching device /dev/sdb
USB device: /sys/devices/pci0000:00/0000:00:12.0/usb3/3-1)
SYNCHRONIZE CACHE: FAILED: No such file or directory
(Continuing despite SYNCHRONIZE CACHE failure.)
STOP UNIT: FAILED: No such file or directory

Doing a file system check on Disk Utility returns File system is clean.. Trying to unmount it via terminal returns this:

~sudo eject /dev/sdb
eject: unable to eject, last error: Invalid argument

I've tried to unmount it on Windows (dual boot system), but I simply got an error message saying that it was unable to eject it. No programs running or anything.

Solution

So, the problem has been solved thanks to Douggro, who helped me in the comments. I'm just reposting his answer here to close the question.

Try ls /media and see if the drive shows there. If it does, sudo umount /media/drivename – douggro

Comments

[douggro]

Have you tried sudo umount /dev/sdb ?

[Gus]

Weird, I get umount: /dev/sdb: not mounted as result. And I'm sure the device is mounted.

[douggro]

Try ls /media and see if the drive shows there. If it does, sudo umount /media/drivename

[Gus]

That worked! But it can be removed without problems just by unmounting? Safely removing still does not work.

[douggro]

Once it's unmounted from /media you should be able to disconnect it from the computer without problem: the filesystem is unmounted at that point.

[Gus]

I see. The problem I'm having is with an USB drive, because it seems to be corrupting the files every time I place them. I thought it was because of removing it incorrectly, but the problem continues. Should I make a new question for it (since the unmount problem has been solved already) or should I edit this question?

[douggro]

If you haven't already, start a new question regarding the corruption - but include this question as a link for background reference.

[David Tonhofer]

@douggro Better run sync; sync before ripping out the cable to flush any buffers to disk in any case. Even if the disk is unmounted, the kernel may still have data to write out to said disk.

[d a i s y]

what to do if it does not ?

[David]

Should not need to eject as root.

[Concurrent EDA]

Edited to use sudo, not sudo su.