1SG_MAP26(8) SG3_UTILS SG_MAP26(8)
2
6 sg_map26 - map SCSI generic (sg) device to corresponding device names
7
9 sg_map26 [--dev_dir=DIR] [--given_is=0|1] [--help] [--result=0|1|2|3]
10 [--symlink] [--verbose] [--version] DEVICE
11
13 Maps a special file (block or char) associated with a SCSI device to
14 the corresponding SCSI generic (sg) device, or vice versa. Can also be
15 given a sysfs file, for example '/sys/block/sda' or
16 '/sys/block/sda/dev'.
17 Rather than map to or from a sg device, the sysfs file name matching a
19 given device special file (or vice versa) can be requested. This is
20 done with '--result=2' and '--result=3'. This feature works on ATA
21 devices (e.g. 'dev/hdc') as well as SCSI devices.
22 In this utility, "mapped" refers to finding the relationship between a
24 SCSI generic (sg) node and the higher level SCSI device name; or vice
25 versa. For example '/dev/sg0' may "map" to '/dev/sda'. Mappings may
26 not exist, if a relevant module is not loaded, for example. Also there
27 are SCSI devices that can only be accessed via a sg node (e.g. SAF-TE
28 and some SES devices).
29 In this utility, "matching" refers to different representations of the
31 same device accessed via the same driver. For example, '/dev/hdc' and
32 '/sys/block/hdc' usually refer to the same device and thus would be
33 considered matching. A related example is that '/dev/cdrom' and
34 '/dev/hdc' are also considered matching if '/dev/cdrom' is a symlink to
35 '/dev/hdc'.
36
38 Arguments to long options are mandatory for short options as well.
39 -d, --dev_dir=DIR
41 where DIR is the directory to search for resultant device spe‐
42 cial files in (or symlinks to same). Only active when
43 '--result=0' (the default) or '--result=2'. If this option is
44 not given and DEVICE is a device special file then the directory
45 part of DEVICE is assumed. If this option is not given and
46 DEVICE is a sysfs name, then if necessary '/dev' is assumed as
47 the directory.
48 -g, --given_is=0 | 1
50 specifies the DEVICE is either a device special file (when the
51 argument is 0), or a sysfs 'dev' file (when the argument is 1).
52 The parent directory of a sysfs 'dev' file is also accepted
53 (e.g. either '/sys/block/sda/dev' or '/sys/block/sda' are
54 accepted). Usually there is no need to give this option since
55 this utility first checks for special files (or symlinks to spe‐
56 cial files) and if not, assumes it has been given a sysfs 'dev'
57 file (or its parent). Generates an error if given and disagrees
58 with variety of DEVICE.
59 -h, --help
61 output the usage message then exit.
62 -r, --result=0 | 1 | 2 | 3
64 specifies what variety of file (or files) that this utility
65 tries to find. The default is a "mapped" device special file,
66 when the argument is 0. When the argument is 1, this utility
67 tries to find the "mapped" sysfs node name. When the argument is
68 2, this utility tries to find the "matching" device special
69 file. When the argument is 3, this utility tries to find the
70 "matching" sysfs node name.
71 -s, --symlink
73 when a device special file is being sought (i.e. when
74 '--result=0' (the default) or '--result=2') then also look for
75 symlinks to that device special file in the same directory.
76 -v, --verbose
78 increase the level of verbosity, (i.e. debug output).
79 -V, --version
81 print the version string and then exit.
82
84 This utility is designed for the Linux 2.6 (and later) kernel series.
85 It uses special file major and minor numbers (and whether the special
86 is block or character) together with sysfs to do its mapping or match‐
87 ing. In the absence of any other information, device special files are
88 assumed to be in the '/dev' directory while sysfs is assumed to be
89 mounted at '/sys'. Device names in sysfs are predictable, given the
90 corresponding major and minor number of the device. However, due to
91 udev rules, the name of device special files can be anything the user
92 desires (e.g. '/dev/sda' could be named '/dev/my_boot_disk'). When try‐
93 ing to find a resultant device special file, this utility uses the
94 major and minor numbers (and whether a block or char device is sought)
95 to search the device directory.
96 This utility only shows one relationship at a time. To get an overview
98 of all SCSI devices, with special file names and optionally the
99 "mapped" sg device name, see the lsscsi utility.
100
102 Assume sg2 maps to sdb while dvd, cdrom and hdc are all matching.
103 # sg_map26 /dev/sg2
105 /dev/sdb
106 # sg_map26 /dev/sdb
108 /dev/sg2
109 # sg_map26 --result=0 /dev/sdb
111 /dev/sg2
112 # sg_map26 --result=3 /dev/sdb
114 /sys/block/sda
115 # sg_map26 --result=1 /dev/sdb
117 /sys/class/scsi_generic/sg0
118 Now look at '/dev/hdc' and friends
120 # sg_map26 /dev/hdc
122 <error: a hd device does not map to a sg device>
123 # sg_map26 --result=3 /dev/hdc
125 /sys/block/hdc
126 # sg_map26 --result=2 /dev/hdc
128 /dev/hdc
129 # sg_map26 --result=2 --symlink /dev/hdc
131 /dev/cdrom
132 /dev/dvd
133 /dev/hdc
134 # sg_map26 --result=2 --symlink /sys/block/hdc
136 /dev/cdrom
137 /dev/dvd
138 /dev/hdc
139
141 The exit status of sg_map26 is 0 when it is successful. Otherwise see
142 the sg3_utils(8) man page.
143
145 Written by Douglas Gilbert.
146
148 Report bugs to <dgilbert at interlog dot com>.
149
151 Copyright © 2005-2012 Douglas Gilbert
152 This software is distributed under a FreeBSD license. There is NO war‐
153 ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
154 POSE.
155
157 udev(7), lsscsi(lsscsi)
158sg3_utils-1.35 November 2012 SG_MAP26(8)