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SG_MAP26(8) SG3_UTILS SG_MAP26(8)
NAME
sg_map26 - map SCSI generic (sg) device to corresponding device names
SYNOPSIS
sg_map26 [--dev_dir=DIR] [--given_is=0|1] [--help] [--result=0|1|2|3] [--symlink] [--ver-
bose] [--version] DEVICE
DESCRIPTION
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 '/sys/block/sda/dev'.
Rather than map to or from a sg device, the sysfs file name matching a given device spe-
cial 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
'/dev/hdc'.
OPTIONS
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 sym-
links 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 dis-
agrees 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 argu-
ment is 1, this utility tries to find the "mapped" sysfs node name. When the argu-
ment 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.
NOTES
This utility is designed for the Linux 2.6 (and later) 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 spe-
cial 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 try-
ing 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 lss-
csi utility.
EXAMPLES
Assume sg2 maps to sdb while dvd, cdrom and hdc are all matching.
# sg_map26 /dev/sg2
/dev/sdb
# sg_map26 /dev/sdb
/dev/sg2
# sg_map26 --result=0 /dev/sdb
/dev/sg2
# sg_map26 --result=3 /dev/sdb
/sys/block/sda
# sg_map26 --result=1 /dev/sdb
/sys/class/scsi_generic/sg0
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
/sys/block/hdc
# sg_map26 --result=2 /dev/hdc
/dev/hdc
# sg_map26 --result=2 --symlink /dev/hdc
/dev/cdrom
/dev/dvd
/dev/hdc
# sg_map26 --result=2 --symlink /sys/block/hdc
/dev/cdrom
/dev/dvd
/dev/hdc
EXIT STATUS
The exit status of sg_map26 is 0 when it is successful. Otherwise see the sg3_utils(8) man
page.
AUTHORS
Written by Douglas Gilbert.
REPORTING BUGS
Report bugs to <dgilbert at interlog dot com>.
COPYRIGHT
Copyright (C) 2005-2012 Douglas Gilbert
This software is distributed under a FreeBSD license. There is NO warranty; not even for
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
SEE ALSO
udev(7), lsscsi(lsscsi)
sg3_utils-1.35 November 2012 SG_MAP26(8)
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