Provided by: sg3-utils_1.17-2_i386 bug

NAME

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

SYNOPSIS

       sg_reset [-b] [-d] [-h] [-V] <scsi_device>

DESCRIPTION

       The  sg_reset  utility  with  no  options  (other than the device name)
       reports on the reset state (e.g. if a reset is underway) of  the  given
       device.  When  given a ’-d’, ’-b’, or ’-h’ option it requests a device,
       bus or host reset respectively.

       In the linux kernel 2.6 series this utility can be  called  on  sd,  sr
       (cd/dvd),   st  or  sg  device  nodes;  if  the  user  has  appropriate
       permissions.

       In the linux kernel 2.4 series support for this utility first  appeared
       in  lk  2.4.19  and  could  only  be called on sg device nodes. Various
       vendors made this capability available in their  kernels  prior  to  lk
       2.4.19.

       -b     attempt  a  SCSI  bus reset. This would normally be tried if the
              device reset (i.e. option ’-d’) was not successful.

       -d     attempt a SCSI device reset. If the device seems stuck, this  is
              the  first  reset  that  should be tried. This assumes the linux
              scsi mid level error handler is not already in  the  process  of
              resetting this device.

       -h     attempt  a  host  adapter reset. This would normally be tried if
              both device reset (i.e. option ’-d’) and bus reset (i.e.  option
              ’-b’) were not successful.

       The  error  recovery  code within the linux kernel when faced with SCSI
       commands timing out and no response from the device (LU), first tries a
       device  reset  and if that is not successful tries a bus reset. If that
       is not successful it tries a host reset. Users of this  utility  should
       check  whether  such  a  recovery  is already underway before trying to
       reset  with  this  utility.  The  "device,bus,host"   order   is   also
       recommended (i.e. first start with the smallest hammer).

       SAM-4  defines  a  hard  reset  (which includes a device power on and a
       transport reset), a logical unit reset and a  I_T  nexus  reset.  A  LU
       reset  and  an  I_T  nexus  reset  can be requested via task management
       function (and support for LU reset is mandatory).  In  Linux  the  SCSI
       subsystem leaves it up to the low level drivers as to whether a "device
       reset" is only for the addressed LU or all the LUs in the  device  that
       contains  the  addressed  LU.   The "bus reset" is a transport reset. A
       "host reset" attempts to re-initialize the HBA that the request  passes
       through  on  route  to the given device. Obviously a "host reset" and a
       "bus reset" can cause collateral damage.

       This utility does not allow individual SCSI commands (or tasks as  they
       are  called in SAM-4) to be aborted. SAM-4 defines ABORT TASK and ABORT
       TASK SET task management functions for that.

AUTHORS

       Written by Douglas Gilbert.

COPYRIGHT

       Copyright © 1999-2005 Douglas Gilbert
       This software is distributed under the  GPL  version  2.  There  is  NO
       warranty;  not  even  for  MERCHANTABILITY  or FITNESS FOR A PARTICULAR
       PURPOSE.