1SG_RESET(8)                        SG3_UTILS                       SG_RESET(8)
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NAME

6       sg_reset - sends SCSI device, bus or host reset; or checks reset state
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SYNOPSIS

9       sg_reset [-b] [-d] [-h] [-V] DEVICE
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DESCRIPTION

12       The sg_reset utility with no options (other than DEVICE) reports on the
13       reset state (e.g. if a reset is underway) of DEVICE. When given  a  -d,
14       -b, or -h option it requests a device, bus or host reset respectively.
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16       In  the  linux  kernel  2.6 series this utility can be called on sd, sr
17       (cd/dvd), st or sg device nodes; if the user  has  appropriate  permis‐
18       sions.
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20       In  the linux kernel 2.4 series support for this utility first appeared
21       in lk 2.4.19 and could only be called on sg device nodes. Various  ven‐
22       dors  made  this  capability  available  in  their  kernels prior to lk
23       2.4.19.
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OPTIONS

26       -b     attempt a SCSI bus reset. This would normally be  tried  if  the
27              device reset (i.e. option -d) was not successful.
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29       -d     attempt  a SCSI device reset. If the device seems stuck, this is
30              the first reset that should be tried.  This  assumes  the  linux
31              scsi  mid  level  error handler is not already in the process of
32              resetting DEVICE.
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34       -h     attempt a host adapter reset. This would normally  be  tried  if
35              both  device  reset  (i.e. option -d) and bus reset (i.e. option
36              -b) were not successful.
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38       -V     prints the version string then exits.
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NOTES

41       The error recovery code within the linux kernel when  faced  with  SCSI
42       commands timing out and no response from the device (LU), first tries a
43       device reset and if that is not successful tries a bus reset.  If  that
44       is  not  successful it tries a host reset. Users of this utility should
45       check whether such a recovery is  already  underway  before  trying  to
46       reset  with  this  utility.  The "device,bus,host" order is also recom‐
47       mended (i.e. first start with the smallest hammer).
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49       SAM-4 defines a hard reset (which includes a  device  power  on  and  a
50       transport  reset),  a  logical  unit  reset and a I_T nexus reset. A LU
51       reset and an I_T nexus reset can be requested via task management func‐
52       tion  (and  support for LU reset is mandatory).  In Linux the SCSI sub‐
53       system leaves it up to the low level drivers as to  whether  a  "device
54       reset"  is  only for the addressed LU or all the LUs in the device that
55       contains the addressed LU.  The "bus reset" is  a  transport  reset.  A
56       "host  reset" attempts to re-initialize the HBA that the request passes
57       through on route to the DEVICE. Obviously a "host  reset"  and  a  "bus
58       reset" can cause collateral damage.
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60       This  utility does not allow individual SCSI commands (or tasks as they
61       are called in SAM-4) to be aborted. SAM-4 defines ABORT TASK and  ABORT
62       TASK SET task management functions for that.
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AUTHORS

65       Written by Douglas Gilbert.
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68       Copyright © 1999-2006 Douglas Gilbert
69       This  software is distributed under the GPL version 2. There is NO war‐
70       ranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR  PUR‐
71       POSE.
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75sg3_utils-1.23                   December 2006                     SG_RESET(8)
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