sg_sanitize man page on DragonFly
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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] [--desc]
[--early] [--fail] [--help] [--invert] [--ipl=LEN] [--overwrite]
[--pattern=PF] [--quick] [--test=TE] [--verbose] [--version] [--wait]
[--zero] 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_request
--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 neither the --early nor --wait option is given then the SANITIZE
command is started with the IMMED bit set. After that this utility
sends a REQUEST SENSE command every 60 seconds until there are no more
progress indications.
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.
-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.
-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.
-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.
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.
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.
AUTHORS
Written by Douglas Gilbert.
REPORTING BUGS
Report bugs to <dgilbert at interlog dot com>.
COPYRIGHT
Copyright © 2011-2014 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-1.40 September 2014 SG_SANITIZE(8)
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