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

Provided by: sg3-utils_1.46-1ubuntu0.22.04.1_amd64

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]   [--overwrite]   [--pattern=PF]   [--quick]
       [--test=TE] [--timeout=SECS] [--verbose] [--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 --overwrite 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 monitor 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 "overwrite" 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 internal 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 overwrite 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 initialization 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 operation 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 initialization 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.

NOTES

The SCSI SANITIZE command is closely related to the ATA SANITIZE command, 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 initialization 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 Terabyte 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
protection 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 format 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 information 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 particular 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!

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  finishes  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 © 2011-2020 Douglas Gilbert
       This software is distributed under a FreeBSD license. There is NO warranty; not  even  for
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.