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       sg_map26  -  maps a special file to a SCSI generic (sg) device (or vice


       sg_map26 [--dev_dir=DIR] [--given_is=0|1]  [--help]  [--result=0|1|2|3]
       [--symlink] [--verbose] [--version] DEVICE


       Maps  a  special  file (block or char) associated with a SCSI device to
       the corresponding SCSI generic (sg) device, or vice versa.  Can also be
       given    a    sysfs    file,    for    example    ’/sys/block/sda’   or

       Rather than map to or from a sg device, the sysfs file name matching  a
       given  device  special  file  (or vice versa) can be requested. This is
       done with ’--result=2’ and ’--result=3’.  This  feature  works  on  ATA
       devices (e.g. ’dev/hdc’) as well as SCSI devices.

       In  this utility, "mapped" refers to finding the relationship between a
       SCSI generic (sg) node and the higher level SCSI device name;  or  vice
       versa.  For  example  ’/dev/sg0’ may "map" to ’/dev/sda’.  Mappings may
       not exist, if a relevant module is not loaded, for example. Also  there
       are  SCSI  devices that can only be accessed via a sg node (e.g. SAF-TE
       and some SES devices).

       In this utility, "matching" refers to different representations of  the
       same  device  accessed via the same driver. For example, ’/dev/hdc’ and
       ’/sys/block/hdc’ usually refer to the same device  and  thus  would  be
       considered  matching.  A  related  example  is  that  ’/dev/cdrom’  and
       ’/dev/hdc’ are also considered matching if ’/dev/cdrom’ is a symlink to


       Arguments to long options are mandatory for short options as well.

       -d, --dev_dir=DIR
              where  DIR  is  the  directory  to  search  for resultant device
              special files  in  (or  symlinks  to  same).  Only  active  when
              ’--result=0’  (the  default)  or ’--result=2’. If this option is
              not given and DEVICE is a device special file then the directory
              part  of  DEVICE  is  assumed.   If this option is not given and
              DEVICE is a sysfs name, then if necessary ’/dev’ is  assumed  as
              the directory.

       -g, --given_is=0 | 1
              specifies  the  DEVICE is either a device special file (when the
              argument is 0), or a sysfs ’dev’ file (when the argument is  1).
              The  parent  directory  of  a  sysfs ’dev’ file is also accepted
              (e.g.   either  ’/sys/block/sda/dev’  or  ’/sys/block/sda’   are
              accepted).  Usually  there  is no need to give this option since
              this utility first checks for  special  files  (or  symlinks  to
              special  files)  and  if  not, assumes it has been given a sysfs
              ’dev’ file (or its parent). Generates  an  error  if  given  and
              disagrees with variety of DEVICE.

       -h, --help
              output the usage message then exit.

       -r, --result=0 | 1 | 2 | 3
              specifies  what  variety  of  file  (or files) that this utility
              tries to find.  The default is a "mapped" device  special  file,
              when  the  argument  is 0.  When the argument is 1, this utility
              tries to find the "mapped" sysfs node name. When the argument is
              2,  this  utility  tries  to  find the "matching" device special
              file. When the argument is 3, this utility  tries  to  find  the
              "matching" sysfs node name.

       -s, --symlink
              when   a   device  special  file  is  being  sought  (i.e.  when
              ’--result=0’ (the default) or ’--result=2’) then also  look  for
              symlinks to that device special file in the same directory.

       -v, --verbose
              increase the level of verbosity, (i.e. debug output).

       -V, --version
              print the version string and then exit.


       This  utility  is  designed  for  the  linux 2.6 kernel series. It uses
       special file major and minor numbers (and whether the special is  block
       or character) together with sysfs to do its mapping or matching. In the
       absence of any other information, device special files are  assumed  to
       be  in  the  ’/dev’  directory  while sysfs is assumed to be mounted at
       ’/sys’. Device names in sysfs are predictable, given the  corresponding
       major  and  minor number of the device. However, due to udev rules, the
       name of device special files can be anything  the  user  desires  (e.g.
       ’/dev/sda’  could  be named ’/dev/my_boot_disk’). When trying to find a
       resultant device special file, this utility uses the  major  and  minor
       numbers  (and  whether  a block or char device is sought) to search the
       device directory.

       This utility only shows one relationship at a time. To get an  overview
       of  all  SCSI  devices,  with  special  file  names  and optionally the
       "mapped" sg device name, see the lsscsi utility.


       Assume sg2 maps to sdb while dvd, cdrom and hdc are all matching.

         # sg_map26 /dev/sg2

         # sg_map26 /dev/sdb

         # sg_map26 --result=0 /dev/sdb

         # sg_map26 --result=3 /dev/sdb

         # sg_map26 --result=1 /dev/sdb

       Now look at ’/dev/hdc’ and friends

         # sg_map26 /dev/hdc
         <error: a hd device does not map to a sg device>

         # sg_map26 --result=3 /dev/hdc

         # sg_map26 --result=2 /dev/hdc

         # sg_map26 --result=2 --symlink /dev/hdc

         # sg_map26 --result=2 --symlink /sys/block/hdc


       The exit status of sg_map26 is 0 when it is successful.  Otherwise  see
       the sg3_utils(8) man page.


       Written by Douglas Gilbert.


       Report bugs to <dgilbert at interlog dot com>.


       Copyright © 2005-2007 Douglas Gilbert
       This  software  is  distributed  under  a  FreeBSD license. There is NO
       warranty; not even for MERCHANTABILITY  or  FITNESS  FOR  A  PARTICULAR


       udev(8), udevinfo(8), lsscsi(lsscsi)