This manual page contains various operating-system specific tips and
tricks on how to get scanners with a SCSI interface working.
For scanners with a SCSI interface, it may be necessary to edit the
appropriate backend configuration file before using SANE for the first
time. For most systems, the configuration file should list the name of
the generic SCSI device that the scanner is connected to (e.g., under
Linux, /dev/sg4 or /dev/sge is such a generic SCSI device). It is cus-
tomary to create a symlink from /dev/scanner to the generic SCSI device
that the scanner is connected to. In this case, the configuration file
simply lists the line /dev/scanner. For a detailed description of each
backend's configuration file, please refer to the relevant backend man-
ual page (e.g., sane-epson(5) for Epson scanners, sane-hp(5) for HP
For some operating systems (e.g. Linux and OS/2), there is an alternate
way of specifying scanner devices. This alternate way allows to iden-
tify scanners by the SCSI vendor and model string and/or by the SCSI
device address (consisting of bus number, channel number, id, and logi-
cal unit number). The syntax for specifying a scanner in this way is:
scsi VENDOR MODEL TYPE BUS CHANNEL ID LUN
where VENDOR is the SCSI vendor string, MODEL is the SCSI model string,
TYPE is type SCSI device type string, BUS is the SCSI bus number (named
"host" in /proc/scsi/scsi), CHANNEL is the SCSI channel number, ID is
the SCSI id, and LUN is the logical unit number of the scanner device.
The first two fields are strings which must be enclosed in double-
quotes if they contain any whitespace. The remaining four fields are
non-negative integer numbers. The correct values for these fields can
be found by using operating system specific tools, e.g. for Linux by
looking at the output of the command "cat /proc/scsi/scsi". To sim-
plify configuration, a field's value can be replaced with an asterisk
symbol (``*''). An asterisk has the effect that any value is allowed
for that particular field. This can have the effect that a single
scsi-line matches multiple devices. When this happens, each matching
device will be probed by the backend one by one and registered if the
backend thinks it is a compatible device. For example, the line
scsi MUSTEK MFS-06000CX Scanner 0 00 03 00
would attach the Mustek SCSI scanner with the following /proc/scsi/scsi
Host: scsi0 Channel: 00 Id: 03 Lun: 00
Vendor: MUSTEK Model: MFS-06000CX Rev: 4.04
Type: Scanner ANSI SCSI revision: 0
Usually it's sufficient to use vendor and model strings only or even
only the vendor string. The following example
form. This is explained below in the relevant platform-specific sec-
When using a SCSI scanner, ensure that the access permission for the
generic SCSI device is set appropriately. We recommend to add a group
"scanner" to /etc/group which contains all users that should have
access to the scanner. The permission of the device should then be set
to allow group read and write access. For example, if the scanner is
at generic SCSI device /dev/sg0, then the following two commands would
set the permission correctly:
$ chgrp scanner /dev/sg0
$ chmod 660 /dev/sg0
When your system uses the device filesystem (devfs), you have to edit
/etc/devfs/perms. There you should search the line
REGISTER ^sg[^/]* PERMISSIONS root.root 0600
and add a new line (eg. for changing permissions of sg4):
REGISTER ^sg4 PERMISSIONS root.scanner 0660
Auto-configuration using the "scsi *" lines in the config files only
works if the user running the frontend has read/write access to
/dev/xpt0. Instead, you can also set a link /dev/scanner to the appro-
priate /dev/uk device.
Reported to work fine under FreeBSD 2.2.2R with the aha
Reported to work fine under FreeBSD 2.2.2.
The scanner probes ok but any attempt to access it hangs
the entire system. It looks like something is disabling
interrupts and then not re-enabling them, so it looks
like a bug in the FreeBSD aic driver.
Works on FreeBSD 2.2.5R and 3.0 using the aic driver,
provided that Plug-and-Play support is disabled on the
card. If there are no uk devices, just do a ``sh MAKEDEV
uk0'' in the /dev directory. The scanner should then be
accessible as /dev/uk0 if it was probed during boot.
Reported to work fine under FreeBSD 2.2.2R with the amd
request a larger scsi buffer, set the environment variable
SANE_SG_BUFFERSIZE to the desired buffer size in bytes. It is not rec-
ommended to use more than 1 MB, because for large values the probabil-
ity increases that the SG driver cannot allocate the necessary buf-
fer(s). For ISA cards, even 1 MB might be a too large value. For a
detailed discussion of memory issues of the SG driver, see
For Linux kernels before version 2.2.7 the size of the buffer is only
32KB. This works, but for many cheaper scanners this causes scanning
to be slower by about a factor of four than when using a size of 127KB.
Linux defines the size of this buffer by macro SG_BIG_BUFF in header
file /usr/include/scsi/sg.h. Unless a system is seriously short on
memory, it is recommended to increase this value to the maximum legal
value of 128*1024-512=130560 bytes. After changing this value, it is
necessary to recompile both the kernel (or the SCSI generic module) and
the SCSI backends. Keep in mind that this is only necessary with older
A common issue with SCSI scanners is what to do when you booted the
system while the scanner was turned off? In such a case, the scanner
won't be recognized by the kernel and SANE won't be able to access it.
Fortunately, Linux provides a simple mechanism to probe a SCSI device
on demand. Suppose you have a scanner connected to SCSI bus 2 and the
scanner has a SCSI id of 5. When the system is up and running and the
scanner is turned on, you can issue the command:
echo "scsi add-single-device 2 0 5 0" > /proc/scsi/scsi
and the kernel will probe and recognize your scanner (this needs to be
done as root). It's also possible to dynamically remove a SCSI device
by using the ``remove-single-device'' command. For details, please
refer to to the SCSI-2.4-HOWTO.
Scanners are known to work with the following SCSI adapters under
Linux. This list isn't complete, usually any SCSI adapter supported by
Linux should work.
Acard/Advance SCSI adapters
Some old versions of the kernel driver (atp870u.c) cut
the inquiry information. Therefore the scanner couldn't
be detected correctly. Use a current kernel.
Reported to work fine with Linux since v2.0. If you
encounter kernel freezes or other unexpected behaviour
get the latest Linux kernel (2.2.17 seems to work) or
reduce SCSI buffer size to 32 kB.
Reported to work fine with Linux v2.0.
NCR/Symbios 53c400/53c400a or Domex DTC3181E/L/LE (DTCT436/436P)
ISA SCSI card
This card is supplied by Mustek (and other vendors). It's
supported since Linux 2.2. The SCSI cards are supported
by the module g_NCR5380. It's necessary to tell the ker-
nel the io port and type of card. Example for a 53c400a:
``modprobe g_NCR5380 ncr_addr=0x280 ncr_53c400a=1''.
Once the kernel detects the card, it should work all
right. However, while it should work, do not expect good
performance out of this card---it has no interrupt line
and therefore while a scan is in progress, the system
becomes almost unusable. You may change the values of
the USLEEP macros in drivers/scsi/g_NCR5380.c. Some doc-
umentation is in this file and NCR5380.c.
For some scanners it may be necessary to disable discon-
nect/reconnect. To achieve this use the option
ncr53c8xx="disc:n". Some people reported that their scan-
ner only worked with the 53c7,8xx driver, not the
ncr53c8xx. Try both if you have trouble.
For Linux kernels before 2.0.33 it may be necessary to
increase the SCSI timeout. The default timeout for the
Linux kernels before 2.0.33 is 10 seconds, which is way
too low when scanning large area. If you get messages of
the form ``restart (ncr dead ?)'' in your /var/log/mes-
sages file or on the system console, it's an indication
that the timeout is too short. In this case, find the
line ``if (np->latetime>10)'' in file ncr53c8xx.c (nor-
mally in directory /usr/src/linux/drivers/scsi) and
change the constant 10 to, say, 60 (one minute). Then
rebuild the kernel/module and try again.
The driver can be downloaded from
http://www.garloff.de/kurt/linux/dc395/. For some older
scanners it may be necessary to disable all the more
advanced features by using e.g. modprobe dc395x_trm
Version 1.11 of the Tekram driver seems to work fine
mostly, except that the scan does not terminate properly
(it causes a SCSI timeout after 10 minutes). The generic
AM53C974 also seems to work fine and does not suffer from
the timeout problems.
SOLARIS, OPENSTEP AND NEXTSTEP INFO
Under Solaris, OpenStep and NeXTStep, the generic SCSI device name
refers to a SCSI bus, not to an individual device. For example,
/dev/sg0 refers to the first SCSI bus. To tell SANE which device to
use, append the character 'a'+target-id to the special device name.
sets the timeout value for SCSI commands in seconds. Overriding
the default value of 120 seconds should only be necessary for
very slow scanners.
sane(7), sane-find-scanner(1), sane-"backendname"(5), sane-usb(5)
14 Jul 2008 sane-scsi(5)
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