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SG_XCOPY(8) SG3_UTILS SG_XCOPY(8)
NAME
sg_xcopy - copy data to and from files and devices using SCSI EXTENDED COPY (XCOPY)
SYNOPSIS
sg_xcopy [bs=BS] [conv=CONV] [count=COUNT] [ibs=BS] [if=IFILE] [iflag=FLAGS] [obs=BS]
[of=OFILE] [oflag=FLAGS] [seek=SEEK] [skip=SKIP] [--help] [--version]
[app=0|1] [bpt=BPT] [cat=0|1] [dc=0|1] [fco=0|1] [id_usage={hold|discard|disable}]
[list_id=ID] [prio=PRIO] [time=0|1] [verbose=VERB] [--on_dst|--on_src] [--verbose]
DESCRIPTION
Copy data to and from any files. Specialized for "files" that are Linux SCSI devices that
support the SCSI EXTENDED COPY (XCOPY) command.
This utility has similar syntax and semantics to dd(1) but with no "conversions" is sup-
ported.
The first group in the synopsis above are "standard" Unix dd(1) operands. The second group
are extra options added by this utility. Both groups are defined below in combined, al-
phabetical order.
By default the XCOPY command is sent to OFILE. This can be changed with the --on_src or
iflag=xflag options which cause the XCOPY command to be sent to IFILE instead. Also see
the section on ENVIRONMENT VARIABLES.
In the SPC-4 standard the T10 committee has expanded the XCOPY command so that it now has
two variants: "LID1" (for a List Identifier length of 1 byte) and "LID4" (for a List Iden-
tifier length of 4 bytes). This utility supports the older, LID1 variant which is also
found in SPC-3 and earlier. While the LID1 variant in SPC-4 is command level (binary) com-
patible with XCOPY as defined in SPC-3, some of the command naming has changed. This util-
ity uses the older, SPC-3 XCOPY names.
The ddpt utility supports the same xcopy(LID1) functionality as this utility with the same
options and flags. Additionally ddpt supports a subset of xcopy(LID4) functionality vari-
ously called "xcopy version 2, lite" or ODX. ODX is a market name and stands for Off-
loaded Data Xfer (i.e. transfer).
OPTIONS
app={0|1}
if 1 start the destination of the copy at the end of OFILE. This assumes that OFILE
is a regular file. The default is 0 in which case the destination of the copy
starts at the beginning of OFILE (possibly offset be SEEK). This option cannot be
used with the seek=SEEK option.
bpt=BPT
each IO transaction will be made using BPT blocks (or less if near the end of the
copy). Default is 128 for logical block sizes less that 2048 bytes, otherwise the
default is 32. So for bs=512 the reads and writes will each convey 64 KiB of data
by default (less if near the end of the transfer or memory restrictions). When
cd/dvd drives are accessed, the logical block size is typically 2048 bytes and bpt
defaults to 32 which again implies 64 KiB transfers.
bs=BS where BS must be the logical block size of the physical device (if either the input
or output files are accessed via SCSI commands). Note that this differs from dd(1)
which permits BS to be an integral multiple. Defaults to the device logical block
size.
cat={0|1}
sets the SCSI EXTENDED COPY command segment descriptor CAT bit to 0 or 1 (default:
0). The CAT bit (in conjunction with the PAD bit) controls the handling of residual
data. See section HANDLING OF RESIDUAL DATA for details.
conv=CONV
all CONV arguments are ignored.
count=COUNT
copy COUNT blocks from IFILE to OFILE. Default is the minimum (IFILE if dc=0 or
OFILE if dc=1) number of blocks that SCSI devices report from SCSI READ CAPACITY
commands or that block devices (or their partitions) report. Normal files are not
probed for their size. If skip=SKIP or seek=SEEK are given and the count is derived
(i.e. not explicitly given) then the derived count is scaled back so that the copy
will not overrun the device. If the file name is a block device partition and COUNT
is not given then the size of the partition rather than the size of the whole de-
vice is used. If COUNT is not given (or count=-1) and cannot be derived then an er-
ror message is issued and no copy takes place.
dc={0|1}
sets the SCSI EXTENDED COPY command segment descriptor DC bit to 0 or 1 (default:
0). The DC bit controls whether COUNT refers to the source (dc=0) or the target
(dc=1) descriptor.
fco={0|1}
sets the SCSI EXTENDED COPY command segment descriptor FCO bit to 0 or 1 (default:
0). The Fast Copy Only (FCO) bit set will result in the copy being done but a tech-
nique faster than SCSI READ and WRITE commands. If the copy cannot but done in a
faster manner then a sense key of "Copy aborted" with and additional sense of "Fast
copy not possible" is returned.
ibs=BS if given must be the same as BS given to 'bs=' option.
id_usage={hold|discard|disable}
sets the SCSI EXTENDED COPY command parameter list field called LIST ID USAGE to 0
if the argument is 'hold', to 2 if the argument is 'discard', or to '3' if the ar-
gument is 'disable'.
If the device has the ability to hold data (as indicated by "held data limit" being
greater than zero) then id_usage defaults to 'hold' otherwise it defaults to 'dis-
card'.
if=IFILE
read from IFILE instead of stdin. If IFILE is '-' then stdin is read. Starts read-
ing at the beginning of IFILE unless SKIP is given.
iflag=FLAGS
where FLAGS is a comma separated list of one or more flags outlined below. These
flags are associated with IFILE and are ignored when IFILE is stdin.
list_id=ID
sets the SCSI EXTENDED COPY command parameter list field called LIST IDENTIFIER to
ID. ID should be a value between 0 and 255 (inclusive). ID usually defaults to 1
unless id_usage=disable in which case it defaults to 0.
obs=BS if given must be the same as BS given to 'bs=' option.
of=OFILE
write to OFILE instead of stdout. If OFILE is '-' then writes to stdout. If OFILE
is /dev/null then no actual writes are performed. If OFILE is '.' (period) then it
is treated the same way as /dev/null (this is a shorthand notation). If OFILE ex-
ists then it is _not_ truncated; it is overwritten from the start of OFILE unless
'oflag=append' or SEEK is given.
oflag=FLAGS
where FLAGS is a comma separated list of one or more flags outlined below. These
flags are associated with OFILE and are ignored when OFILE is /dev/null, '.' (pe-
riod), or stdout.
prio=PRIO
sets the SCSI EXTENDED COPY command parameter list field called PRIORITY to PRIO.
The default value is 1.
seek=SEEK
start writing SEEK bs-sized blocks from the start of OFILE. Default is block 0
(i.e. start of file).
skip=SKIP
start reading SKIP bs-sized blocks from the start of IFILE. Default is block 0
(i.e. start of file).
time={0|1}
when 1, times transfer and does throughput calculation, outputting the results (to
stderr) at completion. When 0 (default) doesn't perform timing.
verbose=VERB
as VERB increases so does the amount of debug output sent to stderr. Default value
is zero which yields the minimum amount of debug output. A value of 1 reports ex-
tra information that is not repetitive. A value 2 reports cdbs and responses for
SCSI commands that are not repetitive (i.e. other that READ and WRITE). Error pro-
cessing is not considered repetitive. Values of 3 and 4 yield output for all SCSI
commands (and Unix read() and write() calls) so there can be a lot of output.
-h, --help
outputs usage message and exits.
--on_dst
send the XCOPY command to the output file/device (i.e. OFILE). This is the default
unless overridden by the --on_src or iflag=xflag options. Also see the section be-
low on ENVIRONMENT VARIABLES.
--on_src
send the XCOPY command to the input file/device (i.e. IFILE).
-v, --verbose
equivalent to verbose=1. When used twice, equivalent to verbose=2, etc.
-V, --version
outputs version number information and exits.
FLAGS
Here is a list of flags and their meanings:
append causes the O_APPEND flag to be added to the open of OFILE. For regular files this
will lead to data appended to the end of any existing data. Cannot be used to-
gether with the seek=SEEK option as they conflict. The default action of this
utility is to overwrite any existing data from the beginning of the file or, if
SEEK is given, starting at block SEEK. Note that attempting to 'append' to a device
file (e.g. a disk) will usually be ignored or may cause an error to be reported.
excl causes the O_EXCL flag to be added to the open of IFILE and/or OFILE.
flock after opening the associated file (i.e. IFILE and/or OFILE) an attempt is made to
get an advisory exclusive lock with the flock() system call. The flock arguments
are "FLOCK_EX | FLOCK_NB" which will cause the lock to be taken if available else a
"temporarily unavailable" error is generated. An exit status of 90 is produced in
the latter case and no copy is done.
null has no affect, just a placeholder.
pad sets the SCSI EXTENDED COPY command segment descriptor PAD bit. The PAD bit (in
conjunction with the CAT bit) controls the handling of residual data.(See section
HANDLING OF RESIDUAL DATA for details.
xcopy has no affect; for compatibility with ddpt.
HANDLING OF RESIDUAL DATA
The pad and cat bits control the handling of residual data. As the data can be specified
either in terms of source or target logical block size and both might have different block
sizes residual data is likely to happen in these cases. If both logical block sizes are
identical these bits have no effect as residual data will not occur.
If none of these bits are set, the EXTENDED COPY command will be aborted with additional
sense 'UNEXPECTED INEXACT SEGMENT'.
If only the cat bit is set the residual data will be retained and made available for sub-
sequent segment descriptors. Residual data will be discarded for the last segment descrip-
tor.
If the pad bit is set for the source descriptor only, any residual data for both source or
destination will be discarded.
If the pad bit is set for the target descriptor only any residual source data will be han-
dled as if the cat bit is set, but any residual destination data will be padded to make a
whole block transfer.
If the pad bit is set for both source and target any residual source data will be dis-
carded, and any residual destination data will be padded.
ENVIRONMENT VARIABLES
If the command line invocation does not explicitly (and unambiguously) indicate whether
the XCOPY SCSI command should be sent to IFILE (i.e. the source) or OFILE (i.e. the des-
tination) then a check is made for the presence of the XCOPY_TO_SRC and XCOPY_TO_DST envi-
ronment variables. If either one exists (but not both) then it indicates where the SCSI
XCOPY command will be sent. By default the XCOPY command is sent to OFILE.
RETIRED OPTIONS
Here are some retired options that are still present:
append=0 | 1
when set, equivalent to 'oflag=append'. When clear the action is to overwrite the
existing file (if it exists); this is the default. See the 'append' flag.
NOTES
Copying data behind an Operating System's back can cause problems. In the case of Linux,
users should look at this link: http://linux-mm.org/Drop_Caches
This command sequence may be useful:
sync; echo 3 > /proc/sys/vm/drop_caches
Various numeric arguments (e.g. SKIP) may include multiplicative suffixes or be given in
hexadecimal. See the "NUMERIC ARGUMENTS" section in the sg3_utils(8) man page.
The COUNT, SKIP and SEEK arguments can take 64 bit values (i.e. very big numbers). Other
values are limited to what can fit in a signed 32 bit number.
All informative, warning and error output is sent to stderr so that dd's output file can
be stdout and remain unpolluted. If no options are given, then the usage message is output
and nothing else happens.
If a device supports xcopy operations then it should set the 3PC field (3PC stands for
Third Party Copy) in its standard INQUIRY response. This utility will attempt a xcopy op-
eration irrespective of the value in the 3PC field but if it is zero (cleared) one would
expect the xcopy operation to fail.
The status of the SCSI EXTENDED COPY command can be queried with sg_copy_re-
sults(sg3_utils)
Currently only block-to-block transfers are implemented; IFILE and OFILE must refer to a
SCSI block device.
No account is taken of partitions so, for example, /dev/sbc2, /dev/sdc, /dev/sg2, and
/dev/bsg/3:0:0:1 would all refer to the same thing: the whole logical unit (i.e. the whole
disk) starting at LBA 0. So any partition indication (e.g. /dev/sdc2) is ignored. The user
should set SKIP, SEEK and COUNT with information obtained from a command like 'fdisk -l
-u /dev/sdc' to account for partitions.
XCOPY (LID1) capability has been added to the ddpt utility which is in a package of the
same name. The ddpt utility will run on other OSes (e.g. FreeBSD and Windows) while
sg_xcopy only runs on Linux. Also ddpt permits the arguments to ibs= and ibs= to be dif-
ferent.
EXAMPLES
Copy 2M of data from the start of one device to another:
# sg_xcopy if=/dev/sdo of=/dev/sdp count=2048 list_id=2 dc=1
sg_xcopy: if=/dev/sdo skip=0 of=/dev/sdp seek=0 count=1024
Start of loop, count=1024, bpt=65535, lba_in=0, lba_out=0
sg_xcopy: 1024 blocks, 1 command
Check the status of the EXTENDED COPY command:
# sg_copy_results --status --list_id=2 /dev/sdp
Receive copy results (copy status):
Held data discarded: Yes
Copy manager status: Operation completed without errors
Segments processed: 1
Transfer count units: 0
Transfer count: 0
SIGNALS
The signal handling has been borrowed from dd: SIGINT, SIGQUIT and SIGPIPE output the num-
ber of remaining blocks to be transferred and the records in + out counts; then they have
their default action. SIGUSR1 causes the same information to be output yet the copy con-
tinues. All output caused by signals is sent to stderr.
EXIT STATUS
The exit status of sg_xcopy is 0 when it is successful. Otherwise see the sg3_utils(8) man
page.
An additional exit status of 90 is generated if the flock flag is given and some other
process holds the advisory exclusive lock.
AUTHORS
Written by Hannes Reinecke and Douglas Gilbert.
REPORTING BUGS
Report bugs to <dgilbert at interlog dot com>.
COPYRIGHT
Copyright (C) 2000-2019 Hannes Reinecke and Douglas Gilbert
This software is distributed under the GPL version 2. There is NO warranty; not even for
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
SEE ALSO
There is a web page discussing sg_dd at http://sg.danny.cz/sg/sg_dd.html
A POSIX threads version of this utility called sgp_dd is in the sg3_utils package. Another
version from that package is called sgm_dd and it uses memory mapped IO to speed transfers
from sg devices.
The lmbench package contains lmdd which is also interesting. For moving data to and from
tapes see dt which is found at http://www.scsifaq.org/RMiller_Tools/index.html
To change mode parameters that effect a SCSI device's caching and error recovery see sd-
parm(sdparm)
See also dd(1), sg_copy_results(sg3_utils), ddrescue(GNU), ddpt,ddptctl(ddpt)
sg3_utils-1.45 February 2019 SG_XCOPY(8)
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