Provided by: sg3-utils_1.40-0ubuntu1_amd64 bug


       sgp_dd - copy data to and from files and devices, especially SCSI devices


       sgp_dd   [bs=BS]  [count=COUNT]  [ibs=BS]  [if=IFILE]  [iflag=FLAGS]  [obs=BS]  [of=OFILE]
       [oflag=FLAGS] [seek=SEEK] [skip=SKIP] [--help] [--version]

       [bpt=BPT]  [coe=0|1]  [cdbsz=6|10|12|16]   [deb=VERB]   [dio=0|1]   [sync=0|1]   [thr=THR]
       [time=0|1] [verbose=VERB]


       Copy  data to and from any files. Specialised for "files" that are Linux SCSI generic (sg)
       and raw devices.  Similar  syntax  and  semantics  to  dd(1)  but  does  not  perform  any
       conversions. Uses POSIX threads to increase the amount of parallelism. This improves speed
       in some cases.

       The first group in the synopsis above are "standard" Unix dd(1) operands. The second group
       are extra options added by this utility.  Both groups are defined below.


              each  IO  transaction will be made using BPT blocks (or less if near the end of the
              copy). Default is 128 for block sizes less that 2048 bytes, otherwise  the  default
              is  32.  So  for  bs=512  the  reads  and writes will each convey 64 KiB of data by
              default (less if near the end of the transfer or memory restrictions). When  cd/dvd
              drives  are accessed, the block size is typically 2048 bytes and bpt defaults to 32
              which again implies 64 KiB transfers.

       bs=BS  where BS must be the block size of the physical device. Note that this differs from
              dd(1)  which  permits  'bs'  to  be an integral multiple of the actual device block
              size. Default is 512 which is usually correct for disks but  incorrect  for  cdroms
              (which normally have 2048 byte blocks).

       cdbsz=6 | 10 | 12 | 16
              size  of  SCSI READ and/or WRITE commands issued on sg device names.  Default is 10
              byte SCSI command blocks (unless calculations indicate that a 4 byte  block  number
              may be exceeded, in which case it defaults to 16 byte SCSI commands).

       coe=0 | 1
              set  to 1 for continue on error. Only applies to errors on sg devices.  Thus errors
              on other files will stop sgp_dd. Default is 0 which implies stop on any error.  See
              the 'coe' flag for more information.

              copy  COUNT blocks from IFILE to OFILE. Default is the minimum (of IFILE and OFILE)
              number of blocks that sg devices report from SCSI READ CAPACITY  commands  or  that
              block  devices  (or their partitions) report. Normal files are not probed for their
              size. If skip=SKIP or skip=SEEK are given and  the  count  is  deduced  (i.e.   not
              explicitly  given) then that count is scaled back so that the copy will not overrun
              the device. If the file name is a block device partition and  COUNT  is  not  given
              then the size of the partition rather than the size of the whole device is used. If
              COUNT is not given and cannot be deduced then an error message  is  issued  and  no
              copy takes place.

              outputs  debug  information.  If  VERB  is  0 (default) then there is minimal debug
              information and as VERB increases so does the amount of  debug  (max  debug  output
              when VERB is 9).

       dio=0 | 1
              default is 0 which selects indirect IO. Value of 1 attempts direct IO which, if not
              available, falls back to indirect IO and notes this at completion. If direct IO  is
              selected  and  /proc/scsi/sg/allow_dio  has the value of 0 then a warning is issued
              (and indirect  IO  is  performed)  For  finer  grain  control  use  'iflag=dio'  or

       ibs=BS if given must be the same as BS given to 'bs=' option.

              read  from  IFILE  instead  of  stdin.  If  IFILE is '-' then stdin is read. Starts
              reading at the beginning of IFILE unless SKIP is given.

              where FLAGS is a comma separated list of one or more flags outlined  below.   These
              flags are associated with IFILE and are ignored when IFILE is stdin.

       obs=BS if given must be the same as BS given to 'bs=' option.

              write  to OFILE instead of stdout. If OFILE is '-' then writes to stdout.  If OFILE
              is /dev/null then no actual writes are performed.  If OFILE is '.' (period) then it
              is  treated  the  same  way  as  /dev/null (this is a shorthand notation). If OFILE
              exists then it is _not_ truncated; it is overwritten from the start of OFILE unless
              'oflag=append' or SEEK is given.

              where  FLAGS  is a comma separated list of one or more flags outlined below.  These
              flags are associated with OFILE and  are  ignored  when  OFILE  is  /dev/null,  '.'
              (period), or stdout.

              start  writing  SEEK  bs-sized  blocks from the start of OFILE.  Default is block 0
              (i.e. start of file).

              start reading SKIP bs-sized blocks from the start of IFILE.   Default  is  block  0
              (i.e. start of file).

       sync=0 | 1
              when  1,  does  SYNCHRONIZE CACHE command on OFILE at the end of the transfer. Only
              active when OFILE is a sg device file name.

              where THR is the number or worker threads (default  4)  that  attempt  to  copy  in
              parallel. Minimum is 1 and maximum is 16.

       time=0 | 1
              when  1,  the transfer is timed and throughput calculation is performed, outputting
              the results (to stderr) at completion. When 0 (default) no timing is performed.

              increase verbosity. Same as  deb=VERB.  Added  for  compatibility  with  sg_dd  and

       --help outputs usage message and exits.

              outputs version number information and exits.


       Here is a list of flags and their meanings:

       append causes  the  O_APPEND  flag to be added to the open of OFILE. For normal files this
              will lead to data appended to the  end  of  any  existing  data.   Cannot  be  used
              together  with  the  seek=SEEK option as they conflict.  The default action of this
              utility is to overwrite any existing data from the beginning of  the  file  or,  if
              SEEK is given, starting at block SEEK. Note that attempting to 'append' to a device
              file (e.g.  a disk) will usually be ignored or may cause an error to be reported.

       coe    continue on error. When given with 'iflag=', an error that is detected in a  single
              SCSI  command  (typically  'bpt'  blocks)  is  noted  (by  an error message sent to
              stderr), then zeros are substituted into the buffer  for  the  corresponding  write
              operation and the copy continues. Note that the sg_dd utility is more sophisticated
              in such error situations when 'iflag=coe'.  When given  with  'oflag=',  any  error
              reported  by  a SCSI WRITE command is reported to stderr and the copy continues (as
              if nothing went wrong).

       dio    request the sg device node associated with this flag does direct IO.  If direct  IO
              is not available, falls back to indirect IO and notes this at completion. If direct
              IO is selected and /proc/scsi/sg/allow_dio has the value of 0  then  a  warning  is
              issued (and indirect IO is performed).

       direct causes  the  O_DIRECT flag to be added to the open of IFILE and/or OFILE. This flag
              requires some memory alignment on IO. Hence user memory buffers are aligned to  the
              page size. Has no effect on sg, normal or raw files.

       dpo    set  the  DPO bit (disable page out) in SCSI READ and WRITE commands. Not supported
              for 6 byte cdb variants of READ and WRITE. Indicates that data is  unlikely  to  be
              required  to stay in device (e.g. disk) cache.  May speed media copy and/or cause a
              media copy to have less impact on other device users.

       dsync  causes the O_SYNC flag to be added to the open of IFILE and/or OFILE.  The  'd'  is
              prepended  to  lower  confusion with the 'sync=0|1' option which has another action
              (i.e. a synchronisation to media at the end of the transfer).

       excl   causes the O_EXCL flag to be added to the open of IFILE and/or OFILE.

       fua    causes the FUA (force unit access)  bit  to  be  set  in  SCSI  READ  and/or  WRITE
              commands.  This  only  has  effect with sg devices. The 6 byte variants of the SCSI
              READ and WRITE commands do not support the FUA bit.  Only active for sg device file

       null   has no affect, just a placeholder.


       Here are some retired options that are still present:

       coe=0 | 1
              continue  on  error  is  0  (off)  by  default.  When  it is 1, it is equivalent to
              'iflag=coe  oflag=coe'  described  in  the  FLAGS  section   above.    Similar   to
              'conv=noerror,sync'  in  dd(1)  utility.  Default is 0 which implies stop on error.
              More advanced coe=1 processing on reads is performed by the sg_dd utility.

       fua=0 | 1 | 2 | 3
              force unit access bit. When 3, fua is set on both IFILE and OFILE; when 2,  fua  is
              set  on  IFILE;,  when  1, fua is set on OFILE; when 0 (default), fua is cleared on
              both. See the 'fua' flag.


       A raw device must be bound to a block device prior to using sgp_dd.  See raw(8)  for  more
       information  about  binding  raw  devices. To be safe, the sg device mapping to SCSI block
       devices should be checked with 'cat /proc/scsi/scsi' before use.

       Raw device partition information can often be found with fdisk(8) [the "-ul"  argument  is
       useful in this respect].

       Various  numeric  arguments (e.g. SKIP) may include multiplicative suffixes or be given in
       hexadecimal. See the "NUMERIC ARGUMENTS" section in the sg3_utils(8) man page.

       The COUNT, SKIP and SEEK arguments can take 64 bit values (i.e. very big  numbers).  Other
       values are limited to what can fit in a signed 32 bit number.

       Data usually gets to the user space in a 2 stage process: first the SCSI adapter DMAs into
       kernel buffers and then the sg driver copies this data into user memory (write  operations
       reverse  this  sequence).   This  is  called  "indirect IO" and there is a 'dio' option to
       select "direct IO" which will DMA directly into user memory. Due to  some  issues  "direct
       IO" is disabled in the sg driver and needs a configuration change to activate it.

       All  informative,  warning and error output is sent to stderr so that dd's output file can
       be stdout and remain unpolluted. If no options are given, then the usage message is output
       and nothing else happens.

       Why  use  sgp_dd? Because in some cases it is twice as fast as dd (mainly with sg devices,
       raw devices give some improvement).  Another reason is that  big  copies  fill  the  block
       device caches which has a negative impact on other machine activity.


       The  signal  handling  has  been  borrowed from dd: SIGINT, SIGQUIT and SIGPIPE output the
       number of remaining blocks to be transferred and the records in + out  counts;  then  they
       have  their default action.  SIGUSR1 causes the same information to be output yet the copy
       continues.  All output caused by signals is sent to stderr.


       Looks quite similar in usage to dd:

          sgp_dd if=/dev/sg0 of=t bs=512 count=1MB

       This will copy 1 million 512 byte blocks from the device associated with  /dev/sg0  (which
       should  have  512 byte blocks) to a file called t.  Assuming /dev/sda and /dev/sg0 are the
       same device then the above is equivalent to:

          dd if=/dev/sda of=t bs=512 count=1000000

       although dd's speed may improve if bs was larger and  count  was  correspondingly  scaled.
       Using a raw device to do something similar on a ATA disk:

          raw /dev/raw/raw1 /dev/hda
          sgp_dd if=/dev/raw/raw1 of=t bs=512 count=1MB

       To copy a SCSI disk partition to an ATA disk partition:

          raw /dev/raw/raw2 /dev/hda3
          sgp_dd if=/dev/sg0 skip=10123456 of=/dev/raw/raw2 bs=512

       This  assumes  a valid partition is found on the SCSI disk at the given skip block address
       (past the 5 GB point of that disk) and that the partition goes to  the  end  of  the  SCSI
       disk. An explicit count is probably a safer option.

       To  do  a fast copy from one SCSI disk to another one with similar geometry (stepping over
       errors on the source disk):

          sgp_dd if=/dev/sg0 of=/dev/sg1 bs=512 coe=1


       The exit status of sgp_dd is 0 when it is successful. Otherwise see the  sg3_utils(8)  man
       page.  Since  this utility works at a higher level than individual commands, and there are
       'coe' and 'retries' flags, individual SCSI command failures do  not  necessary  cause  the
       process to exit.


       Written by Douglas Gilbert and Peter Allworth.


       Report bugs to <dgilbert at interlog dot com>.


       Copyright © 2000-2012 Douglas Gilbert
       This  software  is distributed under the GPL version 2. There is NO warranty; not even for


       A simpler, non-threaded version of this utility but with more advanced "continue on error"
       logic  is  called  sg_dd  and  is also found in the sg3_utils package. The lmbench package
       contains lmdd which is also interesting.  raw(8), dd(1)