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Updated: July 2017

sg_format (1m)


sg_format - format or resize a SCSI disk (perhaps change its block size)


sg_format [--cmplst=0|1]  [--count=COUNT]  [--dcrt]  [--early]  [--fmt-
pinfo=FPI]   [--format]   [--help]   [--long]  [--pfu=PFU]  [--pie=PIE]
[--pinfo]  [--poll=PT]  [--resize]  [--rto_req]  [--security]   [--six]
[--size=SIZE] [--verbose] [--version] [--wait] DEVICE


SG_FORMAT(8)                       SG3_UTILS                      SG_FORMAT(8)

       sg_format  -  format  or  resize  a SCSI disk (perhaps change its block

       sg_format [--cmplst=0|1]  [--count=COUNT]  [--dcrt]  [--early]  [--fmt-
       pinfo=FPI]   [--format]   [--help]   [--long]  [--pfu=PFU]  [--pie=PIE]
       [--pinfo]  [--poll=PT]  [--resize]  [--rto_req]  [--security]   [--six]
       [--size=SIZE] [--verbose] [--version] [--wait] DEVICE

       Not  all  SCSI direct access devices need to be formatted and some have
       vendor specific formatting procedures. SCSI disks with  rotating  media
       are  probably  the  largest  group  that do support a 'standard' format
       operation. They are typically factory formatted to a block size of  512
       bytes  with  the  largest number of blocks that the manufacturer recom-
       mends. The manufacturer's recommendation typically leaves aside a  cer-
       tain  number  of  tracks,  spread across the media, for reassignment of
       blocks to logical block addresses during the life of the disk.

       This utility can format modern SCSI disks and potentially change  their
       block  size (if permitted) and the block count (i.e. number of accessi-
       ble blocks on the media also known as "resizing"). Resizing a  disk  to
       less  than  the  manufacturer's  recommended  block  count is sometimes
       called "short stroking" (see NOTES section). Resizing the  block  count
       while  not  changing the block size may not require a format operation.
       The SBC-2 standard (see www.t10.org) has obsoleted the "format  device"
       mode  page.  Many  of the low level details found in that mode page are
       now left up to the discretion of the manufacturer.

       When this utility is used without options (i.e.  it  is  only  given  a
       DEVICE  argument) it prints out the existing block size and block count
       derived from two sources. These two sources are a block  descriptor  in
       the  response to a MODE SENSE command and the response to a READ CAPAC-
       ITY command. The reason for this double check is to  detect  a  "format
       corrupt"  state  (see  NOTES  section).  This usage will not modify the

       When this utility is used with the "--format" (or "-F") option it  will
       attempt  to  format the given DEVICE. There is a 10 second pause during
       which time the user is invited twice (5 seconds apart) to abort sg_for-
       mat.  This occurs just prior the SCSI FORMAT UNIT command being issued.
       See the NOTES section for more information.

       Protection information is optional and is made up of 8 additional bytes
       associated  with  each logical block. Four protection types are defined
       with protection type 0 being no additional protection  bytes.  See  the
       PROTECTION TYPES section below for more information.

       Arguments to long options are mandatory for short options as well.  The
       options are arranged in alphabetical order based  on  the  long  option

       -C, --cmplst=0 | 1
              sets  the CMPLST ("complete list") bit in the FORMAT UNIT cdb to
              0 or 1.  The default is 1  in  which  case  the  existing  GLIST
              (grown  list)  is  ignored.  If the value is 0 then the existing
              GLIST is taken into account. See the  LISTS  section  below.  In
              most cases this bit should be left set; some MO disk drives need
              this bit cleared.

       -c, --count=COUNT
              where COUNT is the number of blocks to be formatted or media  to
              be  resized  to.  Can  be used with either --format or --resize.
              With --format this option need not be given in which case it  is
              assumed  to  be  zero. With --format the interpretation of COUNT
                (COUNT > 0) : only format the first COUNT blocks and READ
                              CAPACITY will report COUNT blocks after format
                (COUNT = 0) and block size  unchanged  :  use  existing  block
                (COUNT = 0) and block size changed : recommended maximum block
                                                     count for new block size
                (COUNT = -1) : use recommended maximum block count
                (COUNT < -1) : illegal
              With  --resize  this  option  must  be  given and COUNT has this
                (COUNT > 0) : after resize READ CAPACITY will report COUNT
                (COUNT = 0) : after resize READ CAPACITY will report 0 blocks
                (COUNT = -1) : after resize READ CAPACITY will report its
                               maximum number of blocks
                (COUNT < -1) : illegal
              In both cases if the given COUNT exceeds the maximum  number  of
              blocks (for the block size) then the disk reports an error.  See
              NOTES section below.

       -D, --dcrt
              this option sets the DCRT  bit  in  the  FORMAT  UNIT  command's
              parameter list header. It will "disable certification". Certifi-
              cation  verifies  that  blocks  are  usable  during  the  format
              process.  Using  this  option may speed the format.  The default
              action of this utility (i.e. when this option is not  given)  is
              to  clear the DCRT bit thereby requesting "media certification".
              When the DCRT bit is set, the FOV bit must  also  be  set  hence
              sg_format does that.

       -e, --early
              during a format operation, The default action of this utility is
              to poll the disk every 60 seconds to determine the  progress  of
              the  format  operation until it is finished. When this option is
              given this utility will exit "early", that is  as  soon  as  the
              format  operation  has  commenced. Then the user can monitor the
              progress of the ongoing format operation  with  other  utilities
              (e.g.  sg_turs(8) or sg_requests(8)). This option and --wait are
              mutually exclusive.

       -f, --fmtpinfo=FPI
              sets the FMTPINFO field in  the  FORMAT  UNIT  cdb  to  a  value
              between  0  and  3.   The default value is 0. The FMTPINFO field
              from SBC-3 revision 16 is a 2 bit field (bits 7 and 6 of byte  1
              in  the  cdb). Prior to that it was a single bit field (bit 7 of
              byte 1 in the cdb) and there  was  an  accompanying  bit  called
              RTO_REQ  (bit  6  of  byte 1 in the cdb). The deprecated options
              "--pinfo" and "--rto-req" represent the older usage. This option
              should  be used in their place. See the PROTECTION TYPES section
              below for more information.

       -F, --format
              issue a SCSI FORMAT UNIT command.  This  will  destroy  all  the
              data  held  on the media.  This option is required to change the
              block size of a disk. The user is given a 10 second  count  down
              to  ponder the wisdom of doing this, during which time control-C
              (amongst other Unix commands) can be used to kill  this  process
              before  it does any damage. See NOTES section for implementation
              details and EXAMPLES section for typical use.

       -h, --help
              print out the usage information then exit.

       -l, --long
              the default action of this utility is to assume 32  bit  logical
              block addresses. With 512 byte block size this permits more than
              2 terabytes (almost 2 ** 41 bytes) on a single disk. This option
              selects  commands  and  parameters that allow for 64 bit logical
              block addresses.  Specifically this option  sets  the  "longlba"
              flag  in the MODE SENSE (10) command and uses READ CAPACITY (16)
              rather than READ CAPACITY (10). If this option is not given  and
              READ  CAPACITY (10) or MODE SELECT detects a disk the needs more
              than 32 bits to represent its logical  blocks  then  it  is  set
              internally.  This  option  does  not set the LONGLIST bit in the
              FORMAT UNIT command. The LONGLIST bit is set as required depend-
              ing  other  parameters  (e.g.  when  '--pie=PIE' is greater than

       -P, --pfu=PFU
              sets the "Protection Field Usage" field in the  parameter  block
              associated  with a FORMAT UNIT command to PFU. The default value
              is 0, the only other defined value currently is 1. See the  PRO-
              TECTION TYPES section below for more information.

       -q, --pie=PIE
              sets  the  "Protection Interval Exponent" field in the parameter
              block associated with a FORMAT UNIT command to PIE. The  default
              value is 0.  This field first appeared in SBC-3 revision 18.

       -p, --pinfo
              The option is deprecated, use the --fmtpinfo=FPI option instead.
              If used, then it sets bit 7 of byte 1 in the FORMAT UNIT cdb.

       -x, --poll=PT
              where PT is the type of poll used. If PT is 0 then a  TEST  UNIT
              READY  command  is  used,  otherwise  a REQUEST SENSE command is
              used. The default is currently 0 but this will change  to  1  in
              the near future. See the NOTES sections below.

       -r, --resize
              rather  than  format  the  disk,  it  can be resized. This means
              changing the number of blocks on the device reported by the READ
              CAPACITY   command.    This  option  should  be  used  with  the
              --count=COUNT option.  The contents of all logical blocks on the
              media remain unchanged when this option is used. This means that
              any resize operation can be reversed. This option cannot be used
              together with either --format or a --size=SIZE whose argument is
              different to the existing block size.

       -R, --rto_req
              The option is deprecated, use the --fmtpinfo=FPI option instead.
              If used, then it sets bit 6 of byte 1 in the FORMAT UNIT cdb.

       -S, --security
              sets  the  "Security Initialization" (SI) bit in the FORMAT UNIT
              command's initialization pattern descriptor within the parameter
              list.  According  to  SBC-3  the  default initialization pattern
              "shall be written using a security erasure write technique". See
              the NOTES section on the SCSI SANITIZE command.

       -6, --six
              Use  6  byte variants of MODE SENSE and MODE SELECT. The default
              action is to use the 10 byte variants. Some MO drives need  this
              option set when doing a format.

       -s, --size=SIZE
              where  SIZE  is  the  block  size  (i.e. number of bytes in each
              block) to format the device to. The default value is whatever is
              currently  reported by the block descriptor in a MODE SENSE com-
              mand. If the block size given by this option is  different  from
              the  current  value then a MODE SELECT command is used to change
              it prior to the FORMAT UNIT command  being  started  (as  recom-
              mended  in  the  draft  standard). Many SCSI disks have 512 byte
              sectors by default and allow up to 16 bytes extra  in  a  sector
              (i.e. 528 byte sectors).  If the given size in unacceptable with
              the disk, most likely an "Invalid field in parameter list"  mes-
              sage  will  appear  in  sense  data (requires the use of '-v' to
              decode sense data).

       -v, --verbose
              increase the level of verbosity,  (i.e.  debug  output).  "-vvv"
              gives a lot more debug output.

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

       -w, --wait
              the  default format action is to set the "IMMED" bit in the FOR-
              MAT UNIT command's (short)  parameter  header.  If  this  option
              (i.e.  --wait)  is  given  then  the  "IMMED" bit is not set. If
              --wait is given the FORMAT UNIT command waits until  the  format
              operation  completes  before returning its response. This can be
              many hours on large disks. This utility sets a 15  hour  timeout
              on such a FORMAT UNIT command!

       The  SBC-3 draft (revision 29) defines PLIST, CLIST, DLIST and GLIST in
       section 4.13 on "Medium defects". Briefly, the PLIST is  the  "primary"
       list of manufacturer detected defects, the CLIST ("certification" list)
       contains those detected during the format operation,  the  DLIST  is  a
       list of defects that can be given to the format operation. The GLIST is
       the grown list which starts in the format process  as  CLIST+DLIST  and
       can  "grow"  later due to automatic reallocation (see the ARRE and AWRE
       bits in the read-write error recovery mode page  (see  sdparm(8)))  and
       use of the SCSI REASSIGN BLOCKS command (see sg_reassign(8)).

       The  CMPLST  bit  (controlled  by  the  --cmplst=0|1 option) determines
       whether the existing GLIST, when the format operation  is  invoked,  is
       taken  into  account.  The  sg_format  utility sets the FOV bit to zero
       which causes DPRY=0, so the PLIST is taken into account, and DCRT=0, so
       the CLIST is generated and used during the format process.

       The  sg_format  utility does not permit a user to provide a defect list
       (i.e. DLIST).

       SBC-3 drafts have added several "protection types" to  the  "protection
       information"  introduced  in  the  SBC-2  standard. See the "protection
       information" section (section 4.21 in draft SBC-3 rev 29). 8  bytes  of
       protection information are added to each logical block (a 2 byte "logi-
       cal block guard" (CRC), a 2 byte "logical block application guard", and
       a  4  byte  "logical  block reference tag"). SBC-3 defines 4 protection
       types (types 0 to 4) with  protection  type  0  meaning  no  protection
       information is maintained.

       A  device  that  supports  protection information (i.e. supports one or
       more protection types of 1 or higher) sets the  "PROTECT"  bit  in  its
       standard  INQUIRY  response. It also sets the SPT field in the EXTENDED
       INQUIRY VPD page response to indicate which protection  types  it  sup-
       ports.  The  current  protection  type  of  a  disk can be found in the
       "P_TYPE" and "PROT_EN" fields in the response of a READ  CAPACITY  (16)
       command (e.g. with the 'sg_readcap --long' utility).

       Given  that  a device supports a particular protection type, a user can
       then then choose to format that disk with that protection type by  set-
       ting  the  "FMTPINFO" and "Protection Field Usage" fields in the FORMAT
       UNIT command. Those fields correspond to  the  --fmtpinfo=FPI  and  the
       --pfu=PFU  options  in  this  utility. If FPI and PFU are both 0 (their
       default values) then protection type 0 is chosen. If FPI is 2  and  PFU
       is  0  then  protection type 1 is chosen. If FPI is 3 and PFU is 0 then
       protection type 2 is chosen. If FPI is 3 and PFU is 1  then  protection
       type 3 is chosen.

       See attributes(5) for descriptions of the following attributes:

       |Availability   | system/storage/sg3_utils |
       |Stability      | Uncommitted              |
       The SBC-2 standard states that the REQUEST SENSE command should be used
       for obtaining progress indication when the format command is  underway.
       However,  tests on a selection of disks shows that TEST UNIT READY com-
       mands yield progress indications (but not REQUEST SENSE  commands).  So
       the  current  version of this utility defaults to using TEST UNIT READY
       commands to poll the disk to find out the progress of the  format.  The
       --poll=PT option has been added to control this.

       When  the  --format  option is given without the --wait option then the
       SCSI FORMAT UNIT command is issued with the IMMED bit set which  causes
       the  SCSI  command to return after it has started the format operation.
       The --early option will cause sg_format to exit at that point.   Other-
       wise  the  DEVICE  is  polled  every 60 seconds with TEST UNIT READY or
       REQUEST SENSE commands until it reports an "all clear" (i.e. the format
       operation  has  completed). Normally these polling commands will result
       in a progress indicator (expressed as a percentage) being output to the
       screen.   If  the  user  gets  bored  watching the progress report then
       sg_format process can  be  terminated  (e.g.  with  control-C)  without
       affecting  the  format  operation  which continues. However a target or
       device reset (or a power cycle)  will  probably  cause  the  device  to
       become "format corrupt".

       When  the  --format and --wait options are both given then this utility
       may take a long time to return. In this case care should be  taken  not
       to send any other SCSI commands to the disk as it may not respond leav-
       ing those commands queued behind the active format  command.  This  may
       cause a timeout in the OS driver (in a lot shorter period than 15 hours
       applicable to some format operations). This may result in the OS reset-
       ting  the  disk leaving the format operation incomplete. This may leave
       the disk in a "format corrupt" state requiring another format to remedy
       the situation.

       When the block size (i.e. the number of bytes in each block) is changed
       on a disk two SCSI commands must be sent: a MODE SELECT to  change  the
       block  size  followed  by  a FORMAT command. If the MODE SELECT command
       succeeds and the FORMAT fails then the disk may be in a state that  the
       draft  standard  calls "format corrupt". A block descriptor in a subse-
       quent MODE SENSE will report the requested new block size while a  READ
       CAPACITY  command will report the existing (i.e. different) block size.
       Alternatively the READ CAPACITY command may fail, reporting the  device
       is not ready, potentially requiring a format. The solution to this sit-
       uation is to do a format again (and this time the new block  size  does
       not  have  to  be  given) or change the block size back to the original

       The SBC-2 standard states that the block count can be set back  to  the
       manufacturer's  maximum  recommended value in a format or resize opera-
       tion.  This can be done by placing an address of 0xffffffff (or the  64
       bit  equivalent)  in  the  appropriate block descriptor field to a MODE
       SELECT command. In signed (two's complement) arithmetic that value cor-
       responds  to  the  manufacturer's  maximum  recommended  value.  To see
       exactly which SCSI commands are being executed  and  parameters  passed
       add the "-vvv" option to the sg_format command line.

       Short  stroking  is  a technique to trade off capacity for performance.
       Rotating disk performance is usually highest on the outer tracks  (i.e.
       lower logical block addresses) so by resizing or reformatting a disk to
       a smaller capacity, average performance will usually be increased.

       Other utilities may be useful in finding  information  associated  with
       formatting.  These include sg_inq(8) to fetch standard INQUIRY informa-
       tion (e.g. the PROTECT bit) and to fetch the EXTENDED INQUIRY VPD  page
       (e.g.  RTO  and  GRD_CHK  bits).  The  sdparm(8) utility can be used to
       access and potentially change the now obsolete format mode page.

       scsiformat is another utility available for formatting SCSI disks  with
       Linux.  It  dates  from 1997 (most recent update) and may be useful for
       disks whose firmware is of that vintage.

       The COUNT numeric argument may include a multiplicative  suffix  or  be
       given  in  hexadecimal.  See  the  "NUMERIC  ARGUMENTS"  section in the
       sg3_utils(8) man page.

       The SCSI SANITIZE command was introduced in SBC-3 revision  27.  It  is
       closely related to the ATA sanitize disk feature set and can be used to
       remove all existing data from a disk. Sanitize is  more  likely  to  be
       implemented  on  modern disks (including SSDs) than FORMAT UNIT's secu-
       rity initialization feature (see the --security  option)  and  in  some
       cases much faster.

       These  examples  use  Linux  device names. For suitable device names in
       other supported Operating Systems see the sg3_utils(8) man page.

       In the first example below simply find out the existing block count and
       size derived from two sources: a block descriptor in a MODE SELECT com-
       mand response and from the response of a  READ  CAPACITY  commands.  No
       changes are made:

          sg_format /dev/sdm

       Now a simple format, leaving the block count and size as they were pre-
       viously.  The FORMAT UNIT command is executed in  IMMED  mode  and  the
       device is polled every 60 seconds to print out a progress indication:

          sg_format --format /dev/sdm

       Now the same format, but waiting (passively) until the format operation
       is complete:

          sg_format --format --wait /dev/sdm

       Next is a format in which the block size is changed to  520  bytes  and
       the  block  count  is set to the manufacturer's maximum value (for that
       block size). Note, not all disks support changing the block size:

          sg_format --format --size=520 /dev/sdm

       Now a resize operation so that only the first 0x10000 (65536) blocks on
       a disk are accessible. The remaining blocks remain unaltered.

          sg_format --resize --count=0x10000 /dev/sdm

       Now resize the disk back to its normal (maximum) block count:

          sg_format --resize --count=-1 /dev/sdm

       Format with type 1 protection:

          sg_format --format --fmtpinfo=2 /dev/sdm

       Format with type 3 protection:

          sg_format --format --fmtpinfo=3 --pfu /dev/sdm

       The  exit status of sg_format is 0 when it is successful. Otherwise see
       the sg3_utils(8) man page. Unless the --wait option is given, the  exit
       status  may  not reflect the success of otherwise of the format.  Using
       sg_turs(8) and sg_readcap(8) after the format operation may be wise.

       Written by Grant Grundler, James Bottomley and Douglas Gilbert.

       Report bugs to <dgilbert at interlog dot com>.

       Copyright (C) 2005-2012 Grant Grundler,  James  Bottomley  and  Douglas
       This  software is distributed under the GPL version 2. There is NO war-
       ranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR  PUR-

       sg_turs(8), sg_requests(8), sg_inq(8), sg_modes(8), sg_vpd(8), sg_reas-
       sign(8),   sg_readcap(8),   sg3_utils(8),   sg_sanitize(8)   [all    in
       sg3_utils], sdparm(8), scsiformat (old), hdparm(8)

       This     software     was    built    from    source    available    at
       https://java.net/projects/solaris-userland.   The  original   community
       source was downloaded from  http://sg.danny.cz/sg/p/sg3_utils-1.33.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-1.33                   January 2012                     SG_FORMAT(8)