man > sg_map(8)

SG_MAP(8)                                     SG3_UTILS                                    SG_MAP(8)

NAME
       sg_map - displays mapping between Linux sg and other SCSI devices

SYNOPSIS
       sg_map [-a] [-h] [-i] [-n] [-scd] [-sd] [-sr] [-st] [-V] [-x]

DESCRIPTION
       Sometimes  it  is  difficult  to determine which SCSI device a sg device name (e.g. /dev/sg0)
       refers to. This command loops through the sg devices and finds the corresponding  SCSI  disk,
       cdrom  or tape device name (if any). Scanners are an example of SCSI devices that have no al‐
       ternate SCSI device name apart from their sg device name.

       This utility is deprecated and has not been updated for years, only very obvious bugs will be
       fixed. Unless a very old version of Linux is being used (e.g.  2.4 series or  earlier),  then
       please use a utility like lsscsi(8) or the facilities offered by udev(8).

OPTIONS
       -a     assume  the  sg  devices  have  alphabetical  device  names and loop through /dev/sga,
              /dev/sgb, etc. Default is numeric scan.  Note that sg device nodes with an  alphabeti‐
              cal index have been deprecated since the Linux kernel 2.2 series.

       -h     print usage message then exit.

       -i     in  addition do a standard INQUIRY and output vendor, product and revision strings for
              devices that are found.

       -n     assume the sg devices have numeric device names and loop through  /dev/sg0,  /dev/sg1,
              etc. Default is numeric scan

       -scd   display mappings to SCSI cdrom device names of the form /dev/scd0, /dev/scd1 etc

       -sd    display mappings to SCSI disk device names

       -sr    display mappings to SCSI cdrom device names of the form /dev/sr0, /dev/sr1 etc

       -st    display mappings to SCSI tape device names

       -V     print out version string then exit (without further ado).

       -x     after  each  active  sg  device name is displayed there are five digits: <host_number>
              <bus> <scsi_id> <lun> <scsi_type>

NOTES
       If no options starting with "-s" are given then the mapping to all SCSI disk, cdrom and  tape
       device names is shown.

       If the device file system (devfs) is present a line noting this is output. The "native" devfs
       scsi  hierarchy  makes  the relationship between a sg device name and any corresponding disk,
       cdrom or tape device name easy to establish. This replaces the need for this command. However
       many applications will continue to look for Linux SCSI  device  names  in  their  traditional
       places. [Devfs supplies a compatibility daemon called devfsd whose default configuration adds
       back the Linux device names in their traditional positions.

       Quite  often  the  mapping information can be derived by observing the output of the command:
       "cat /proc/scsi/scsi".  However if devices have been added since boot this can be deceptive.

       In the Linux kernel 2.6 series something close to the mapping shown by this  utility  can  be
       found  by  analysing  sysfs. The main difference is that sysfs analysis will show the mapping
       between sg nodes and other SCSI device nodes in terms of major and minor numbers. While major
       8, minor 16 will usually be /dev/sdb this is not necessarily so. Facilities  associated  with
       udev  may  assign  major  8, minor 16 some other device node name. This version of sg_map has
       been extended to cope with sparse disk device node names of  the  form  "/dev/sd<str>"  where
       <str>  can  be  one  of  [a-z,aa-zz,aaa-zzz]. See the sg_map26 utility for a more precise way
       (i.e. less directory scanning) for mapping between sg device names and  higher  level  names;
       including finding user defined names.

       This  utility  was  written  at  a time when hotplugging of SCSI devices was not supported in
       Linux. It used a simple algorithm to scan sg device nodes in ascending numeric or  alphabeti‐
       cal order, stopping after there were 5 consecutive errors.

       In the Linux kernel 2.6 series, this utility uses sysfs to find which sg device nodes are ac‐
       tive  and  only  checks those. Hence there can be large "holes" in the numbering of sg device
       nodes (e.g. after an adapter has been removed) and still all active sg device nodes  will  be
       listed.  This utility assumes that sg device nodes are named using the normal conventions and
       searches from /dev/sg0 to /dev/sg4095 inclusive.

EXAMPLES
       My system has a SCSI disk, a cd writer and a dvd player:
          $ sg_map
          # Note: the devfs pseudo file system is present
          /dev/sg0  /dev/sda
          /dev/sg1  /dev/sr0
          /dev/sg2  /dev/sr1

       In order to find which sg device name corresponds to the disk:
          $ sg_map -sd
          # Note: the devfs pseudo file system is present
          /dev/sg0  /dev/sda
          /dev/sg1
          /dev/sg2

       The "-x" option gives the following output:
          sg_map -x
          # Note: the devfs pseudo file system is present
          /dev/sg0  1 0 1 0  0  /dev/sda
          /dev/sg1  2 0 4 0  5  /dev/sr0
          /dev/sg2  2 0 6 0  5  /dev/sr1

       When a SCSI scanner is added the output becomes:
          $ sg_map
          # Note: the devfs pseudo file system is present
          /dev/sg0  /dev/sda
          /dev/sg1  /dev/sr0
          /dev/sg2  /dev/sr1
          /dev/sg3

       By process of elimination /dev/sg3 must be the scanner.

EXIT STATUS
       The exit status of sg_map is 0 when it is successful.  Otherwise  see  the  sg3_utils(8)  man
       page.

AUTHOR
       Written by Douglas Gilbert

REPORTING BUGS
       Report bugs to <dgilbert at interlog dot com>.

COPYRIGHT
       Copyright © 2000-2013 Douglas Gilbert
       This software is distributed under the GPL version 2. There is NO warranty; not even for MER‐
       CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

SEE ALSO
       sg_map26(8) , scsi_info(8) , scsidev(8) , devfsd(8) , lsscsi(8) , udev(7)

sg3_utils-1.36                                May 2013                                     SG_MAP(8)