I have a problem with a USB 3 port on a desktop running Debian Linux. The problem started when a system backup was attempted to a portable hard drive plugged into the USB 3 port. The backup operation had previously been done many times with no problems. This time the mount operation failed with a message of the type 'can't find UUID=....' Various commands such as fdisk -l showed that the kernel was not detecting the drive. The drive was unplugged, then replug with a dmesg command issued straight after the replug. The dmesg output seemed to indicate the portable hard drive itself had some problem. A new portable hard drive was plugged into the port, but the kernel could not see the new drive, although a slowly flashing light on the drive indicated some power was reaching the hard drive. I thought that perhaps the port was not supplying enough power to the drive, so I then plugged a new USB flash drive into the port. However the kernel would not recognise the flash drive. Someone subsequently suggested that perhaps the power pins of the port were working but not the data pins. This could perhaps be due to a problem with the port's USB header or associated cabling or possibly due to damage to the host controller or associated wiring. Any thoughts on this, please.