This is not a question on how to umount a drive.
I have a 2nd gen ipod nano (old) that works great but has 0 battery life.
I figure if I plug it into the raspberry, it can power it and it does. However, the ipod comes up with the Do not disconnect icon as if it is mounted. lsblk indicates it is connected at /dev/sda and df indicates that it is not mounted. In gui, by unmounting the drive this message goes away while still charging it.
I can only access the rpi by cli (ssh) and I am using raspbian.
Update: Testing it in Linux Mint 17.1, I inserted it, and then removed it with the gui. Interestingly, after doing so it isn't detected in lsusb when initially plugging it in, it is. That makes me wonder - can I do that manually in cli?