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man pages section 8: System Administration Commands

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Updated: Wednesday, February 9, 2022
 
 

sg_sanitize (8)

Name

sg_sanitize - remove all user data from disk with SCSI SANITIZE command

Synopsis

sg_sanitize  [--ause]  [--block]  [--count=OC]  [--crypto]  [--dry-run]
[--desc] [--early] [--fail] [--help]  [--invert]  [--ipl=LEN]  [--over-
write]  [--pattern=PF]  [--quick]  [--test=TE] [--timeout=SECS] [--ver-
bose] [--version] [--wait] [--zero] [--znr] DEVICE

Description

SG_SANITIZE(8)                     SG3_UTILS                    SG_SANITIZE(8)



NAME
       sg_sanitize - remove all user data from disk with SCSI SANITIZE command

SYNOPSIS
       sg_sanitize  [--ause]  [--block]  [--count=OC]  [--crypto]  [--dry-run]
       [--desc] [--early] [--fail] [--help]  [--invert]  [--ipl=LEN]  [--over-
       write]  [--pattern=PF]  [--quick]  [--test=TE] [--timeout=SECS] [--ver-
       bose] [--version] [--wait] [--zero] [--znr] DEVICE

DESCRIPTION
       This utility invokes the SCSI SANITIZE command. This command was  first
       introduced  in the SBC-3 revision 27 draft. The purpose of the sanitize
       operation is to alter the information in the cache and on the medium of
       a  logical  unit (e.g. a disk) so that the recovery of user data is not
       possible. If that user data cannot be erased, or is in the  process  of
       being  erased, then the sanitize operation prevents access to that user
       data.

       Once a SCSI SANITIZE command has successfully started, then  user  data
       from  that  disk  is  no  longer  available.  Even if the disk is power
       cycled, the sanitize operation will continue after power is re-instated
       until it is complete.

       This  utility  requires either the --block, --crypto, --fail or --over-
       write option. With the --block, --crypto or --overwrite option the user
       is  given  15  seconds to reconsider whether they wish to erase all the
       data on a disk, unless the --quick option is given in  which  case  the
       sanitize  operation  starts  immediately.  The  disk's INQUIRY response
       strings are printed out just in case the wrong DEVICE has been given.

       If the --early option is given then this utility will exit  soon  after
       starting the SANITIZE command with the IMMED bit set. The user can mon-
       itor the progress of  the  sanitize  operation  with  the  "sg_requests
       --num=9999  --progress"  which  sends  a REQUEST SENSE command every 30
       seconds. Otherwise if the --wait option is given then this utility will
       wait  until  the  SANITIZE command completes (or fails) and that can be
       many hours.

       If the --wait option is not given then the SANITIZE command is  started
       with  the  IMMED bit set. If neither the --early nor the --wait options
       are given then this utility sends a REQUEST SENSE command  after  every
       60  seconds  until there are no more progress indications in which case
       this utility exits silently. If additionally the  --verbose  option  is
       given  the  exit  will  be  marked by a short message that the sanitize
       seems to have succeeded.

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

       -A, --ause
              sets the AUSE bit in the cdb. AUSE  is  an  acronym  for  "allow
              unrestricted  sanitize exit". The default action is to leave the
              AUSE bit cleared.

       -B, --block
              perform a "block erase" sanitize operation.

       -c, --count=OC
              where OC is the "overwrite count"  associated  with  the  "over-
              write"  sanitize  operation.  OC can be a value between 1 and 31
              and 1 is the default.

       -C, --crypto
              perform a "cryptographic erase" sanitize  operation.  Note  that
              this erase is often very quick as it simply overwrites an inter-
              nal cryptographic key with a  new  value.  Those  keys  are  not
              accessible  to  users  and encrypt all data written then decrypt
              all data read from the media. The primary reason for doing  that
              is  to  make  this  operation  fast.  This  operation can not be
              reversed.

       -d, --desc
              sets the DESC field  in  the  REQUEST  SENSE  command  used  for
              polling.  By  default this field is set to zero. A REQUEST SENSE
              polling loop is  used  after  the  SANITIZE  command  is  issued
              (assuming  that  neither  the --early nor the --wait option have
              been given) to check on the progress of this command as  it  can
              take some time.

       -D, --dry-run
              this  option will parse the command line, do all the preparation
              but bypass the actual SANITIZE command.

       -e, --early
              the default action of this utility is to poll the disk every  60
              seconds  to  fetch the progress indication until the sanitize is
              finished. When this option  is  given  this  utility  will  exit
              "early"  as  soon as the SANITIZE command with the IMMED bit set
              to 1 has been acknowledged. This option and --wait  cannot  both
              be given.

       -F, --fail
              perform  an  "exit  failure  mode" sanitize operation. Typically
              requires the preceding SANITIZE command to  have  set  the  AUSE
              bit.

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

       -i, --ipl=LEN
              set  the  initialization pattern length to LEN bytes. By default
              it is set to the length of the pattern file (PF)  or  4  if  the
              --zero  option is given. Only active when the --overwrite option
              is also given. It is the number of bytes from the PF  file  that
              will be used as the initialization pattern (if the --zero option
              is not given).  The minimum size is 1 byte and  the  maximum  is
              the  logical block size of the DEVICE (and not to exceed 65535).
              If LEN exceeds the PF file size then the initialization  pattern
              is padded with zeros.

       -I, --invert
              set  the  INVERT  bit  in the overwrite service action parameter
              list. This only affects the "overwrite" sanitize operation.  The
              default  is  a clear INVERT bit. When the INVERT bit is set then
              the initialization pattern is inverted between consecutive over-
              write passes.

       -O, --overwrite
              perform  an  "overwrite" sanitize operation. When this option is
              given then the --pattern=PF or the --zero option is required.

       -p, --pattern=PF
              where PF is the filename of a file containing the initialization
              pattern  required  by  an  "overwrite"  sanitize  operation. The
              length of this file will be used as the length of  the  initial-
              ization pattern unless the --ipl=LEN option is given. The length
              of the initialization pattern must be  from  1  to  the  logical
              block size of the DEVICE.

       -Q, --quick
              the  default  action  (i.e.  when the option is not given) is to
              give the user 15 seconds to reconsider doing a  sanitize  opera-
              tion  on  the DEVICE.  When this option is given that step (i.e.
              the 15 second warning period) is skipped.

       -T, --test=TE
              set the TEST field in the  overwrite  service  action  parameter
              list.  This only affects the "overwrite" sanitize operation. The
              default is to place 0 in that field.

       -t, --timeout=SECS
              where SECS is the number of seconds used for the timeout on  the
              SANITIZE command.

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

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

       -w, --wait
              the  default  action  (i.e.  without this option and the --early
              option) is to start the SANITIZE command with the IMMED bit  set
              then  poll  for  the  progress indication with the REQUEST SENSE
              command until the sanitize operation  is  complete  (or  fails).
              When  this option is given (and the --early option is not given)
              then the SANITIZE command is started with the IMMED  bit  clear.
              For  a  large disk this might take hours. [A cryptographic erase
              operation could potentially be very quick.]

       -z, --zero
              with an "overwrite" sanitize operation this  option  causes  the
              initialization  pattern to be zero (4 zeros are used as the ini-
              tialization pattern).  Cannot  be  used  with  the  --pattern=PF
              option.  If this option is given twice (e.g. '-zz') then 0xff is
              used as the initialization byte.

       -Z, --znr
              sets ZNR bit (zoned no reset) in cdb. Introduced  in  the  SBC-4
              revision 7 draft.


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


       +---------------+--------------------------+
       |ATTRIBUTE TYPE |     ATTRIBUTE VALUE      |
       +---------------+--------------------------+
       |Availability   | system/storage/sg3_utils |
       +---------------+--------------------------+
       |Stability      | Pass-through uncommitted |
       +---------------+--------------------------+

NOTES
       The  SCSI  SANITIZE command is closely related to the ATA SANITIZE com-
       mand, both are relatively new with the ATA command being the first  one
       defined.   The  SCSI  to  ATA Translation (SAT) definition for the SCSI
       SANITIZE command appeared in the SAT-3 revision 4 draft.

       When a SAT layer is used to a (S)ATA disk then for OVERWRITE  the  ini-
       tialization  pattern  must  be  4  bytes long. So this means either the
       --zero option may be given, or a pattern file  (with  the  --pattern=PF
       option)  that  is 4 bytes long or set to that length with the --ipl=LEN
       option.

       The SCSI SANITIZE command is related to the SCSI FORMAT  UNIT  command.
       It is likely that a block erase sanitize operation would take a similar
       amount of time as a format on the same disk (e.g. 9 hours for a 2  Ter-
       abyte  disk).  The primary goal of a format is the configuration of the
       disk at the end of a format (e.g. different logical block size or  pro-
       tection  information added). Removal of user data is only a side effect
       of a format.  With the SCSI SANITIZE command, removal of user  data  is
       the  primary  goal.   If  a sanitize operation is interrupted (e.g. the
       disk is power cycled) then after power up any remaining user data  will
       not  be available and the sanitize operation will continue. When a for-
       mat is interrupted (e.g. the disk is power cycled) the drafts say  very
       little  about  the  state of the disk. In practice some of the original
       user data may remain and the format may need to be restarted.

       Finding out whether a disk (SCSI or ATA) supports  SANITIZE  can  be  a
       challenge.  If  the user really needs to find out and no other informa-
       tion is available then  try  'sg_sanitize  --fail  -vvv  <device>'  and
       observe  the  sense data returned may be the safest approach. Using the
       --fail variant of this utility should have no effect unless it  follows
       an  already  failed  sanitize  operation.  If the SCSI REPORT SUPPORTED
       OPERATION CODES command (see sg_opcodes) is  supported  then  using  it
       would be a better approach for finding if sanitize is supported.

       If using the dd command to check the before and after data of a partic-
       ular block (i.e. check the erase actually worked) it is a good idea  to
       use  the  'iflag=direct'  operand.  Otherwise  the  first read might be
       cached and returned when the same LBA is read a little later. Obviously
       this  utility  should  only  be  used  to sanitize data on a disk whose
       mounted file systems (if any) have been unmounted prior to the erase!

       Source code for open source software components in Oracle  Solaris  can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-
       code-downloads.html.

       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-1.46.tgz.

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

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

       As a precaution if this utility is called with no  options  then  apart
       from printing a usage message, nothing happens:

          sg_sanitize /dev/sdm

       To  do  a  "block  erase" sanitize the --block option is required.  The
       user will be given a 15 second period to reconsider, the SCSI  SANITIZE
       command  will be started with the IMMED bit set, then this utility will
       poll for a progress indication with a REQUEST SENSE command  until  the
       sanitize operation is finished:

          sg_sanitize --block /dev/sdm

       To  start a "block erase" sanitize and return from this utility once it
       is started (but not yet completed) use the --early option:

          sg_sanitize --block --early /dev/sdm

       If the 15 second reconsideration time is not required add  the  --quick
       option:

          sg_sanitize --block --quick --early /dev/sdm

       To do an "overwrite" sanitize a pattern file may be given:

          sg_sanitize --overwrite --pattern=rand.img /dev/sdm

       If  the  length  of  that  "rand.img" is 512 bytes (a typically logical
       block size) then to use only the first 17  bytes  (repeatedly)  in  the
       "overwrite" sanitize operation:

          sg_sanitize --overwrite --pattern=rand.img --ipl=17 /dev/sdm

       To overwrite with zeros use:
          sg_sanitize --overwrite --zero /dev/sdm

EXIT STATUS
       The  exit  status  of sg_sanitize 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.

       The  Unix  convention  is that "no news is good news" but that can be a
       bit unnerving after an operation like sanitize, especially if  it  fin-
       ishes quickly (i.e. before the first progress poll is sent). Giving the
       --verbose option once should supply enough additional output to  settle
       those nerves.

AUTHORS
       Written by Douglas Gilbert.

REPORTING BUGS
       Report bugs to <dgilbert at interlog dot com>.

COPYRIGHT
       Copyright (C) 2011-2020 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-
       POSE.

SEE ALSO
       sg_requests(8), sg_format(8)




sg3_utils-1.46                   December 2020                  SG_SANITIZE(8)