Provided by: sg3-utils_1.33-1_amd64 bug


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


       sg_format  [--cmplst=0|1]  [--count=COUNT]  [--dcrt] [--early] [--fmtpinfo=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 recommends.  The
       manufacturer's  recommendation  typically  leaves aside a certain 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 accessible 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 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 CAPACITY command. The reason for this double check is to detect a "format  corrupt"
       state (see NOTES section). This usage will not modify the disk.

       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_format. 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 name.

       -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

       -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 is:
                (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
                (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 interpretation:
                (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". Certification  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  depending  other  parameters  (e.g.  when
              '--pie=PIE' is greater than zero).

       -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 PROTECTION 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 command. 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  recommended  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" message 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

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

       -w, --wait
              the  default  format  action is to set the "IMMED" bit in the FORMAT 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

       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 "logical 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
       supports. 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'

       Given  that a device supports a particular protection type, a user can then then choose to
       format that disk with that protection type by setting 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.


       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 commands 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.   Otherwise  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 leaving 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 resetting 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 subsequent
       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 situation 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 size.

       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 operation.  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  corresponds
       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 information (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

       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 security initialization feature (see the --security option) and in some cases  much


       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 command 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 previously.  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 © 2005-2012 Grant Grundler, James Bottomley and Douglas Gilbert
       This software is distributed under the GPL version 2. There is NO warranty; not  even  for


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