eject - eject removable media
When you umount /mnt/usb, sometimes the LED is still on, then you can try this
eject /mnt/usb
screen - screen manager with VT100/ANSI terminal emulation
SYNOPSIS
screen [ -options ] [ cmd [ args ] ]
screen -r [[pid.]tty[.host]]
screen -r sessionowner/[[pid.]tty[.host]]
lftp -
To be continued ...