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man pages section 8: System Administration Commands

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Updated: Thursday, June 13, 2019

sg_write_buffer (8)


sg_write_buffer - send SCSI WRITE BUFFER commands


sg_write_buffer     [--bpw=CS]     [--help]    [--id=ID]    [--in=FILE]
[--length=LEN] [--mode=MO] [--offset=OFF] [--raw] [--skip=SKIP] [--spe-
cific=MS] [--timeout=TO] [--verbose] [--version] DEVICE


SG_WRITE_BUFFER(8)                 SG3_UTILS                SG_WRITE_BUFFER(8)

       sg_write_buffer - send SCSI WRITE BUFFER commands

       sg_write_buffer     [--bpw=CS]     [--help]    [--id=ID]    [--in=FILE]
       [--length=LEN] [--mode=MO] [--offset=OFF] [--raw] [--skip=SKIP] [--spe-
       cific=MS] [--timeout=TO] [--verbose] [--version] DEVICE

       Sends one or more SCSI WRITE BUFFER commands to DEVICE, along with data
       provided by the user. In some cases no data is required, or data can be
       read  from the file given in the --in=FILE option, or data is read from
       stdin when either --raw or --in=- is given.

       Some WRITE BUFFER command variants do not have associated data to  send
       to  the  device. For example "activate_mc" activates deferred microcode
       that was sent via prior WRITE BUFFER commands.  There  is  a  different
       method   used   to   download   microcode   to  SES  devices,  see  the
       sg_ses_microcode utility.

       Arguments to long options are mandatory for short options as well.

       -b, --bpw=CS
              where CS is the chunk size in bytes. This will  be  the  maximum
              number  of bytes sent per WRITE BUFFER command. So if CS is less
              than the effective length then multiple  WRITE  BUFFER  commands
              are  sent,  each  taking  the  next chunk from the read data and
              increasing the buffer offset field in the WRITE  BUFFER  command
              by  the  appropriate  amount.  The  default is a chunk size of 0
              which is interpreted as a very large number hence only one WRITE
              BUFFER  command  will  be  sent. This option should only be used
              with modes that "download microcode, with offsets  ...";  namely
              either mode 0x6, 0x7, 0xd or 0xe.
              The number in CS can optionally be followed by ",act" or ",acti-
              vate".  In this case after WRITE BUFFER commands have been  sent
              until  the  effective  length  is exhausted another WRITE BUFFER
              command with its mode set to "Activate deferred microcode  mode"
              [mode 0xf] is sent.

       -h, --help
              output  the usage message then exit. If used multiple times also
              prints the mode names and their acronyms.

       -i, --id=ID
              this option sets the buffer id field in the cdb. ID is  a  value
              between 0 (default) and 255 inclusive.

       -I, --in=FILE
              read data from file FILE that will be sent with the WRITE BUFFER
              command.  If FILE is '-' then stdin is  read  until  an  EOF  is
              detected  (this  is the same action as --raw). Data is read from
              the beginning of FILE except in the case when it  is  a  regular
              file and the --skip=SKIP option is given.

       -l, --length=LEN
              where  LEN is the length, in bytes, of data to be written to the
              device.  If not given (and the length  cannot  be  deduced  from
              --in=FILE  or  --raw)  then  defaults  to zero. If the option is
              given and the length deduced from --in=FILE or --raw is less (or
              no data is provided), then bytes of 0xff are used as fill bytes.

       -m, --mode=MO
              this  option  sets  the  MODE  field  in  the cdb. MO is a value
              between 0 (default) and 31 inclusive. Alternatively an abbrevia-
              tion  can  be  given.   See the MODES section below. To list the
              available mode abbreviations at run time  give  an  invalid  one
              (e.g. '--mode=xxx') or use the '-hh' option.

       -o, --offset=OFF
              this  option  sets  the BUFFER OFFSET field in the cdb. OFF is a
              value between 0 (default) and 2**24-1 . It is a byte offset.

       -r, --raw
              read data from stdin until an EOF is detected. This data is sent
              with  the  WRITE  BUFFER  command  to DEVICE. The action of this
              option is the same as using '--in=-'.

       -s, --skip=SKIP
              this option is only active when --in=FILE is given and FILE is a
              regular  file,  rather than stdin. Data is read starting at byte
              offset SKIP  to  the  end  of  file  (or  the  amount  given  by
              --length=LEN).  If not given the byte offset defaults to 0 (i.e.
              the start of the file).

       -S, --specific=MS
              MS is the MODE SPECIFIC field in the cdb. This is a 3-bit  field
              so  the values 0 to 7 are accepted. This field was introduced in
              SPC-4 revision 32 and can be used to specify  additional  events
              that activate deferred microcode (when MO is 0xD).

       -t, --timeout=TO
              TO  is  the  command  timeout (in seconds) for each WRITE BUFFER
              command issued by this utility. Its default value is 300 seconds
              (5  minutes)  and  should  only be altered if this is not suffi-

       -v, --verbose
              increase the level of verbosity, (i.e. debug output).

       -V, --version
              print the version string and then exit.

       Following is a list of WRITE  BUFFER  command  settings  for  the  MODE
       field.   First  is an acronym accepted by the MO argument of this util-
       ity.  Following the acronym in square brackets  are  the  corresponding
       decimal and hex values that may also be given for MO. The following are
       listed in numerical order.

       hd  [0, 0x0]
              Combined header and data (obsolete in SPC-4).

       vendor  [1, 0x1]
              Vendor specific.

       data  [2, 0x2]
              Data (was called "Write Data" in SPC-3).

       dmc  [4, 0x4]
              Download microcode and activate (was called "Download microcode"
              in SPC-3).

       dmc_save  [5, 0x5]
              Download  microcode,  save,  and  activate (was called "Download
              microcode and save" in SPC-3).

       dmc_offs  [6, 0x6]
              Download microcode with offsets and activate (was called  "Down-
              load microcode with offsets" in SPC-3).

       dmc_offs_save  [7, 0x7]
              Download  microcode with offsets, save, and activate (was called
              "Download microcode with offsets and save" in SPC-3).

       echo  [10, 0xa]
              Write data to echo buffer (was called "Echo buffer" in SPC-3).

       dmc_offs_ev_defer  [13, 0xd]
              Download microcode with offsets, select activation events, save,
              and defer activate (introduced in SPC-4).

       dmc_offs_defer  [14, 0xe]
              Download  microcode  with  offsets,  save,  and  defer  activate
              (introduced in SPC-4).

       activate_mc  [15, 0xf]
              Activate deferred microcode (introduced in SPC-4).

       en_ex  [26, 0x1A]
              Enable expander communications protocol and Echo  buffer  (obso-
              lete in SPC-4).

       dis_ex  [27, 0x1B]
              Disable expander communications protocol (obsolete in SPC-4).

       deh  [28, 0x1C]
              Download  application client error history (was called "Download
              application log" in SPC-3).

       See attributes(7) for descriptions of the following attributes:

       |Availability   | system/storage/sg3_utils |
       |Stability      | Pass-through uncommitted |
       If no --length=LEN is given this utility reads up to 8 MiB of data from
       the  given file FILE (or stdin). If a larger amount of data is required
       then the --length=LEN option should be given.

       The user should be aware that most operating systems have limits on the
       amount  of  data  that can be sent with one SCSI command. In Linux this
       depends on the pass through mechanism used (e.g. block SG_IO or the  sg
       driver) and various setting in sysfs in the Linux lk 2.6/3 series (e.g.
       /sys/block/sda/queue/max_sectors_kb). Devices (i.e. logical units) also
       typically  have limits on the maximum amount of data they can handle in
       one command. These two limitations suggest that  modes  containing  the
       word  "offset"  together  with  the  --bpw=CS  option  are  required as
       firmware files get larger and larger. And CS can be  quite  small,  for
       example 4096 bytes, resulting in many WRITE BUFFER commands being sent.

       Attempting  to download a microcode/firmware file that is too large may
       cause an error to occur in the pass-through layer (i.e. before the SCSI
       command  is  issued).  In Linux such error reports can be obscure as in
       "pass through os error invalid argument". FreeBSD reports  such  errors
       well  to  the  machine's console but returns a cryptic error message to
       this utility.

       Downloading incorrect microcode into a device has the ability to render
       that  device inoperable. One would hope that the device vendor verifies
       the data before activating it. If the  SCSI  WRITE  BUFFER  command  is
       given  values  in  its  cdb (e.g. LEN) that are inappropriate (e.g. too
       large) then the device should respond  with  a  sense  key  of  ILLEGAL
       REQUEST  and  an  additional  sense  code of INVALID FIELD in CDB. If a
       WRITE BUFFER command (or a sequence of them) fails due to device vendor
       verification  checks then it should respond with a sense key of ILLEGAL
       REQUEST and an additional sense code of COMMAND SEQUENCE ERROR.

       All numbers given with options are assumed  to  be  decimal.   Alterna-
       tively  numerical values can be given in hexadecimal preceded by either
       "0x" or "0X" (or has a trailing "h" or "H").

       The following sends new firmware to an enclosure. Sending a 1.5 MB file
       in one WRITE BUFFER command caused the enclosure to lock up temporarily
       and did not update the firmware. Breaking the firmware file into  4  KB
       chunks (an educated guess) was more successful:

         sg_write_buffer -b 4k -m dmc_offs_save -I firmware.bin /dev/sg4

       The  firmware  update  occurred in the following enclosure power cycle.
       With a modern enclosure the Extended Inquiry VPD page gives indications
       in which situations a firmware upgrade will take place.

       The  exit  status of sg_write_buffer is 0 when it is successful. Other-
       wise see the sg3_utils(8) man page.

       Written by Luben Tuikov and Douglas Gilbert.

       Report bugs to <dgilbert at interlog dot com>.

       Copyright (C) 2006-2015 Luben Tuikov and Douglas Gilbert
       This software is distributed under a FreeBSD license. There is NO  war-
       ranty;  not  even  for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR-

       sg_read_buffer, sg_ses_microcode(sg3_utils)

       This    software    was    built    from    source     available     at
       https://github.com/oracle/solaris-userland.    The  original  community
       source was downloaded from  http://sg.danny.cz/sg/p/sg3_utils-1.42.tgz

       Further information about this software can be found on the open source
       community website at http://sg.danny.cz/sg/sg3_utils.html.

sg3_utils-1.41                   February 2015              SG_WRITE_BUFFER(8)