Restart/reset USB in Ubuntu 12.04 without rebooting

      Sometimes USB devices will not get identified or locked in Ubuntu 12.04. To resolve this issue without restart, you can use the below command to do it.

Note: You need sudo/root permission to execute the below commands.

Either place the following into a script or run the commands directly:

echo -n "0000:00:1a.0" | tee /sys/bus/pci/drivers/ehci_hcd/unbind
echo -n "0000:00:1d.0" | tee /sys/bus/pci/drivers/ehci_hcd/unbind
echo -n "0000:00:14.0" | tee /sys/bus/pci/drivers/xhci_hcd/unbind
echo -n "0000:00:1a.0" | tee /sys/bus/pci/drivers/ehci_hcd/bind
echo -n "0000:00:1d.0" | tee /sys/bus/pci/drivers/ehci_hcd/bind
echo -n "0000:00:14.0" | tee /sys/bus/pci/drivers/xhci_hcd/bind

The hardware identifiers being passed around here can be revealed using a command like lspci | grep USB. 

Courtesy: http://davidjb.com/blog/2012/06/restartreset-usb-in-ubuntu-12-04-without-rebooting/