path: root/doc/sg_sanitize.8

.TH SG_SANITIZE "8" "June 2011" "sg3_utils\-1.32" SG3_UTILS
.SH NAME
sg_sanitize \- remove all use data from a SCSI disk
.SH SYNOPSIS
.B sg_sanitize
[\fI\-\-block\fR] [\fI\-\-count=OC\fR] [\fI\-\-crypto\fR] [\fI\-\-early\fR]
[\fI\-\-help\fR] [\fI\-\-invert\fR] [\fI\-\-ipl=LEN\fR] [\fI\-\-overwrite\fR]
[\fI\-\-pattern=PF\fR] [\fI\-\-quick\fR] [\fI\-\-verbose\fR]
[\fI\-\-version\fR] [\fI\-\-wait\fR]
\fIDEVICE\fR
.SH DESCRIPTION
.\" Add any additional description here
.PP
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.
.PP
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. 
.PP
This utility requires either the \fI\-\-block\fR, \fI\-\-crypto\fR or
\fI\-\-overwrite\fR option. If the \fI\-\-quick\fR option is not given
then the user if given 15 seconds to reconsider whether they wish to
erase all the data on a disk. The disk's INQUIRY response strings
are printed out just in case the wrong \fIDEVICE\fR has been given.
.PP
If the \fI\-\-early\fR option is given 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_request \-\-num=9999 \-\-progress" which sends a REQUEST SENSE
command every 30 seconds. Otherwise if the \fI\-\-wait\fR option is given
then this utility will wait until the SANITIZE command completes (or fails)
and that can be many hours.
.PP
If neither the \fI\-\-early\fR nor \fI\-\-wait\fR 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.
.SH 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.
.TP
\fB\-B\fR, \fB\-\-block\fR
perform a "block erase" sanitize operation.
.TP
\fB\-c\fR, \fB\-\-count\fR=\fIOC\fR
where \fIOC\fR is the "overwrite count" associated with the "overwrite"
sanitize operation. \fIOC\fR can be a value between 1 and 31 and 1 is
the default.
.TP
\fB\-C\fR, \fB\-\-crypto\fR
perform a "cryptographic erase" sanitize operation.
.TP
\fB\-e\fR, \fB\-\-early\fR
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
has commenced. This option and \fI\-\-wait\fR cannot both be given.
.TP
\fB\-h\fR, \fB\-\-help\fR
print out the usage information then exit.
.TP
\fB\-i\fR, \fB\-\-ipl\fR=\fILEN\fR
set the initialization pattern length to \fILEN\fR bytes. By default it is
set to the length of the pattern file (\fIPF\fR). Only active when the
\fI\-\-overwrite\fR option is also given. It is the number of bytes from
the \fIPF\fR file that will be used as the initialization pattern. The
minimum size is 1 byte and the maximum is the logical block size of the
\fIDEVICE\fR (and not to exceed 65535). If \fILEN\fR exceeds the \fIPF\fR
file size then the initialization pattern is padded with zeros.
.TP
\fB\-I\fR, \fB\-\-invert\fR
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.
.TP
\fB\-O\fR, \fB\-\-overwrite\fR
perform an "overwrite" sanitize operation. When this option is given
then the \fI\-\-pattern=PF\fR option is required.
.TP
\fB\-p\fR, \fB\-\-pattern\fR=\fIPF\fR
where \fIPF\fR 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 \fI\-\-ipl=LEN\fR option is given. The length of the initialization
pattern must be from 1 to the logical block size of the \fIDEVICE\fR.
.TP
\fB\-Q\fR, \fB\-\-quick\fR
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 \fIDEVICE\fR. 
When this option is given that step (i.e. the 15 second warning period)
is skipped.
.TP
\fB\-v\fR, \fB\-\-verbose\fR
increase the level of verbosity, (i.e. debug output).
.TP
\fB\-V\fR, \fB\-\-version\fR
print the version string and then exit.
.TP
\fB\-w\fR, \fB\-\-wait\fR
the default action (i.e. without this option and the \fI\-\-early\fR 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
\fI\-\-early\fR 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.]
.SH 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.
It is likely that a SCSI to ATA Translation (SAT) definition will soon
appear for the SCSI SANITIZE command (most likely in SAT\-3).
.PP
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. 
.SH EXAMPLES
These examples use Linux device names. For suitable device names in
other supported Operating Systems see the sg3_utils(8) man page.
.PP
As a precaution if this utility is called with no options then apart from
printing a usage message, nothing happens:
.PP
   sg_sanitize /dev/sdm
.PP
To do a "block erase" sanitize the \fI\-\-block\fR 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:
.PP
   sg_sanitize \-\-block /dev/sdm
.PP
To start a "block erase" sanitize and return from this utility once it is
started (but not yet completed) use the \fI\-\-early\fR option:
.PP
   sg_sanitize \-\-block \-\-early /dev/sdm
.PP
If the 15 second reconsideration time is not required add the
\fI\-\-quick\fR option:
.PP
   sg_sanitize \-\-block \-\-quick \-\-early /dev/sdm
.PP
To do an "overwrite" sanitize a pattern file is required:
.PP
   sg_sanitize \-\-overwrite \-\-pattern=rand.img /dev/sdm
.PP
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:
.PP
   sg_sanitize \-\-overwrite \-\-pattern=rand.img \-\-ipl=17 /dev/sdm
.PP
.SH EXIT STATUS
The exit status of sg_sanitize is 0 when it is successful. Otherwise see
the sg3_utils(8) man page. Unless the \fI\-\-wait\fR option is given, the
exit status may not reflect the success of otherwise of the format.
.SH AUTHORS
Written by Douglas Gilbert.
.SH "REPORTING BUGS"
Report bugs to <dgilbert at interlog dot com>.
.SH COPYRIGHT
Copyright \(co 2011 Douglas Gilbert
.br
This software is distributed under a FreeBSD license. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
.SH "SEE ALSO"
.B sg_requests(8), sg_format(8)