Provided by: libsane-common_1.1.1-5ubuntu1_all bug


       sane-usb - USB configuration tips for SANE


       This  manual  page contains information on how to access scanners with a USB interface. It
       focuses on two main topics: getting the scanner detected by the  operating  system  kernel
       and using it with SANE.

       This  page  applies  to  USB most backends and scanners, as they use the generic sanei_usb
       interface.  However,  there  is   one   exception:   USB   Scanners   supported   by   the
       sane-microtek2(5) backend need a special USB kernel driver.


       This is a short HOWTO-like section. For the full details, read the following sections. The
       goal of this section is to get the scanner detected by sane-find-scanner(1).

       Run sane-find-scanner(1).  If it lists your scanner with the correct  vendor  and  product
       ids, you are done. See section SANE ISSUES for details on how to go on.

       sane-find-scanner(1)  doesn't  list your scanner? Does it work as root? If yes, there is a
       permission issue.  See the LIBUSB section for details.

       Nothing is found even as root? Check that your kernel supports  USB  and  that  libusb  is
       installed (see section LIBUSB).


       For  accessing  USB  devices,  the USB library libusb is used. There used to exist another
       method to access USB devices: the kernel scanner driver. The kernel scanner driver  method
       is  deprecated  and shouldn't be used anymore. It may be removed from SANE at any time. In
       Linux, the kernel scanner driver has been removed in the 2.6.* kernel series. Only  libusb
       access is documented in this manual page.


       SANE  can  only  use libusb 0.1.6 or newer. It needs to be installed at build-time. Modern
       Linux distributions and other operating systems come with libusb.

       Libusb can only access your scanner if it's not claimed by the kernel scanner  driver.  If
       you  want  to  use  libusb,  unload  the kernel driver (e.g. rmmod scanner under Linux) or
       disable the driver when compiling a new kernel. For Linux, your kernel needs  support  for
       the USB filesystem (usbfs). For kernels older than 2.4.19, replace "usbfs" with "usbdevfs"
       because the name has changed. This filesystem must be mounted. That's  done  automatically
       at boot time, if /etc/fstab contains a line like this:

              none /proc/bus/usb usbfs defaults  0  0

       The  permissions  for  the  device  files used by libusb must be adjusted for user access.
       Otherwise only root  can  use  SANE  devices.  For  Linux,  the  devices  are  located  in
       /proc/bus/usb/ or in /dev/bus/usb, if you use udev. There are directories named e.g. "001"
       (the bus name) containing files "001", "002" etc. (the device  files).  The  right  device
       files  can  be  found  out  by  running:  scanimage  -L: as root. Setting permissions with
       chmod(1) is not permanent, however. They will be reset  after  reboot  or  replugging  the

       Usually  udev(7)  or for older distributions the hotplug utilities are used, which support
       dynamic setting of access permissions. SANE comes with udev and  hotplug  scripts  in  the
       directory  tools/udev  and  tools/hotplug.   They can be used for setting permissions, see
       /usr/share/doc/libsane/README.linux, tools/README and  the  README  in  the  tools/hotplug
       directory for more details.

       For  the  BSDs,  the device files used by libusb are named /dev/ugen*.  Use chmod to apply
       appropriate permissions.


       This section assumes that your scanner is detected by  sane-find-scanner(1).   It  doesn't
       make sense to go on, if this is not the case. While sane-find-scanner(1) is able to detect
       any USB scanner, actual scanning will only work if the scanner  is  supported  by  a  SANE
       backend.  Information  on  the  level  of  support  can  be  found  on  the  SANE  webpage
       (, and the individual backend manpages.

       Most backends can detect USB scanners automatically using "usb" configuration file  lines.
       This  method  allows  one to identify scanners by the USB vendor and product numbers.  The
       syntax for specifying a scanner this way is:

              usb VENDOR PRODUCT

       where VENDOR is the USB vendor id, and PRODUCT is the USB product id of the scanner.  Both
       ids  are non-negative integer numbers in decimal or hexadecimal format. The correct values
       for these fields can be found by running sane-find-scanner(1),  looking  into  the  syslog
       (e.g., /var/log/messages) or under Linux by issuing the command cat /proc/bus/usb/devices.
       This is an example of a config file line:

              usb 0x055f 0x0006

       would have the effect that all USB devices in the system with a vendor id of 0x55f  and  a
       product id of 0x0006 would be probed and recognized by the backend.

       If your scanner is not detected automatically, it may be necessary to edit the appropriate
       backend configuration file  before  using  SANE  for  the  first  time.   For  a  detailed
       description  of  each  backend's  configuration file, please refer to the relevant backend
       manual page (e.g.  sane-mustek_usb(5) for Mustek USB scanners).

       Do not create a symlink from /dev/scanner to the USB device because this link is  used  by
       the SCSI backends. The scanner may be confused if it receives SCSI commands.


              If  the  library was compiled with debug support enabled, this environment variable
              controls the debug level for the USB I/O subsystem.  E.g., a value of 128  requests
              all  debug  output  to be printed.  Smaller levels reduce verbosity. Values greater
              than   4   enable   libusb    debugging    (if    available).    Example:    export

              If  your  scanner  does  not  work  when  plugged into a USB3 port, try setting the
              environment variable SANE_USB_WORKAROUND to 1. This may work  around  issues  which
              happen with particular kernel versions. Example: export SANE_USB_WORKAROUND=1.


       sane(7), sane-find-scanner(1), sane-"backendname"(5), sane-scsi(5)


       Henning Meier-Geinitz <>

                                           14 Jul 2008                                sane-usb(5)