On Linux, eject will work, but will not really "finish the job" regarding USB rotating drives.
So first, you eject /dev/sdb (or umount everything).
And then, after proper unmounting, the best way to unplug a USB external hard-drive is:
udisksctl power-off -b /dev/sdb or
udisks --detach /dev/sdb This usually causes the drive to spin down gracefully.
Note: udisksctl might be a more "mainstream" tool, compared to udisks (the former is already installed on my Debian, the latter isn't & has been criticised for unnecessary spin up/down).
Some details
udisksctl
The documentation states (about the power-off option):
Arranges for the drive to be safely removed and powered off. On the OS side this includes ensuring that no process is using the drive, then requesting that in-flight buffers and caches are committed to stable storage. The exact steps for powering off the drive depends on the drive itself and the interconnect used. For drives connected through USB, the effect is that the USB device will be deconfigured followed by disabling the upstream hub port it is connected to.
Note that as some physical devices contain multiple drives (for example 4-in-1 flash card reader USB devices) powering off one drive may affect other drives. As such there are not a lot of guarantees associated with performing this action. Usually the effect is that the drive disappears as if it was unplugged.
udisks (deprecated?)
Precisely, the current implementation (as of 2014):
- sends SCSI sync-cache command,
- sends SCSI stop command,
- unbinds the usb-storage kernel driver,
- suspends the USB device (power),
- logically disables/removes it from its USB port.
This process is close to the manual procedure that is suggested here. Initial answer was on askubuntu.
