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When attempting to access an external USB drive, loading of the USB modules may be required. Follow the steps below to find out which modules to load in order for the kernel to recognize the device.

First, to ensure the device has been recognized by the kernel, execute the following command in a terminal:

dmesg

The output should be similar to the following:

 
hub.c: new USB device 00:1d.7-1, assigned address 3
scsi1 : SCSI emulation for USB Mass Storage devices
  Vendor: WDC WD25  Model: 00JB-00EVA0       Rev:  0 0
  Type:   Direct-Access                      ANSI SCSI revision: 02
Attached scsi disk sdb at scsi1, channel 0, id 0, lun 0
SCSI device sdb: 488397168 512-byte hdwr sectors (250059 MB)
 sdb: sdb1 sdb2 sdb3 sdb4
WARNING: USB Mass Storage data integrity not assured

This output shows that the external disk has been recognized as /dev/sdb and there are 4 partitions: /dev/sdb1, /dev/sdb2, /dev/sdb3, /dev/sdb4. These partitions can now be mounted normally.

If you are having problems mounting the partitions and get error messages similar to device cannot be found or invalid device, then the correct host controller driver may not be loaded.

To find out which modules are needed to be loaded, run the following command from a command line:

lspci -v | grep HCI

 
# lspci -v | grep HCI
00:02.2 USB Controller: Silicon Integrated Systems [SiS] 7001 (rev 07) 
  (prog-if 10 [OHCI])
00:02.3 USB Controller: Silicon Integrated Systems [SiS] 7001 (rev 07) 
  (prog-if 10 [OHCI])
00:0b.0 USB Controller: NEC Corporation USB (rev 41) (prog-if 10 [OHCI])
00:0b.1 USB Controller: NEC Corporation USB (rev 41) (prog-if 10 [OHCI])
00:0b.2 USB Controller: NEC Corporation USB 2.0 (rev 01) 
  (prog-if 20 [EHCI])
00:0f.0 USB Controller: VIA Technologies, Inc. USB (rev 50) 
  (prog-if 00 [UHCI])
00:0f.1 USB Controller: VIA Technologies, Inc. USB (rev 50) 
  (prog-if 00 [UHCI])
00:0f.2 USB Controller: VIA Technologies, Inc. USB 2.0 (rev 51) 
  (prog-if 20 [EHCI])
00:11.0 USB Controller: OPTi Inc. 82C861 (rev 10) (prog-if 10 [OHCI])

There are three types of host controller interfaces (HCI). They are:

From this output, all types of HCIs are supported on this system.

To have a USB drive recognized that is connected to one of these HCIs, simply load the corresponding driver.

For example, to load the usb-uhci and usb-ohci modules use the following commands:

 
modprobe usb-uhci
modprobe usb-ohci

After loading the correct modules, reconnect the USB drive to the system and retry the steps mentioned at the start of this article.

For more information on USB devices under Linux, refer to the Linux USB Project at http://www.linux-usb.org/.