1DDPT(8) DDPT DDPT(8)
2
6 ddpt - copies data between files and storage devices. Support for de‐
7 vices that understand the SCSI command set.
8
10 ddpt [bpt=BPT[,OBPC]] [bs=BS] [cdbsz=IO_CDBSZ] [cdl=CDL] [coe={0|1}]
11 [coe_limit=CL] [conv=CONVS] [count=COUNT] [ddpt=VERS] [delay=MS[,W_MS]]
12 [ibs=IBS] [id_usage=LIU] if=IFILE [iflag=FLAGS] [intio={0|1}]
13 [iseek=SKIP] [ito=ITO] [list_id=LID] [obs=OBS] [of=OFILE] [of2=OFILE2]
14 [oflag=FLAGS] [oseek=SEEK] [prio=PRIO] [protect=RDP[,WRP]] [re‐
15 tries=RETR] [rtf=RTF] [rtype=RTYPE] [seek=SEEK] [skip=SKIP] [sta‐
16 tus=STAT] [to=TO] [verbose=VERB] [--dry-run] [--flexible] [--help]
17 [--job=JF] [--odx] [--prefetch] [--progress] [--quiet] [--verbose]
18 [--verify] [--version] [--wscan] [--xcopy] [ddpt] [JF]
19 For comparison here is the synopsis for GNU's dd command:
21 dd [bs=BS] [cbs=CBS] [conv=CONVS] [count=COUNT] [ibs=IBS] [if=IFILE]
23 [iflag=FLAGS] [obs=OBS] [of=OFILE] [oflag=FLAGS] [seek=SEEK]
24 [skip=SKIP] [status=STAT] [--help] [--version]
25
27 Copies data between files or simply reads data from a file. Alterna‐
28 tively if the --verify option is given, the IFILE and OFILE contents
29 are compared, stopping if an inequality is found. This utility is spe‐
30 cialized for "files" that are storage devices, especially those that
31 can use the SCSI command sets (e.g. SATA and SAS disks). It can issue
32 SCSI commands in pass-through ("pt") mode. Similar syntax and semantics
33 to the Unix dd(1) command.
34 For comparison, the SYNOPSIS section above shows both the ddpt command
36 line operands and options followed by GNU's dd(1) command line operands
37 and options. Broadly speaking ddpt can be considered a super-set of dd.
38 See the section on DD DIFFERENCES for significant differences between
39 ddpt and dd.
40 This utility either does direct copies, based on read-write sequences,
42 or offloaded copies. In an offloaded copy the data being copied does
43 not necessarily pass through the memory of the the machine originating
44 the copy operation; this can save a significant amount of time and
45 lessen CPU usage.
46 When doing a direct copy, this utility breaks the copy into segments
48 since computer RAM is typically a scarce resource. First it reads in
49 BPT*IBS bytes from IFILE (or less if near the end of the copy) into a
50 copy buffer. In the absence of the various operand and flags that by‐
51 pass the write operation, the copy buffer is then written out to OFILE.
52 The copy process continues working its way along IFILE and OFILE until
53 either COUNT is exhausted, an end of file is detected, or an error oc‐
54 curs. If IBS and OBS are different, ddpt restricts the value of OBS
55 such that the copy buffer is an integral number of output blocks (i.e.
56 (((IBS * BPT) % OBS) == 0) ). In the following descriptions, "segment"
57 refers to all or part of a copy buffer.
58 The term "pt device" is used for a pass-through device to which SCSI
60 commands like READ(10), WRITE(10) or POPULATE TOKEN may be sent. A pt
61 device may only be able to process SCSI commands in which case the "pt"
62 flag is assumed. The ability to recognize such a pt only device may
63 vary depending on the operating system (e.g. in Linux /dev/sg2 and
64 /dev/bsg/3:0:1:0 are recognized). However if a device can process ei‐
65 ther normal UNIX read()/ write() calls or pass-through SCSI commands
66 then the default is to use UNIX read()/write() calls. That default can
67 be overridden by using the "pt" flag (e.g. "if=/dev/sdc iflag=pt").
68 When pt access is specified any partition information is ignored. So
69 "if=/dev/sdc2 iflag=pt skip=3" will start at logical block address 3 of
70 '/dev/sdc'. As a protection measure ddpt will only accept that if the
71 force flag is also given (i.e. 'iflag=pt,force').
72 This utility supports two types of offloaded copies. Both are based on
74 the EXTENDED COPY (XCOPY or xcopy) family of SCSI commands. The first
75 uses the XCOPY(LID1) command to do a disk to disk copy. LID1 stands for
76 List IDentifier length of 1 byte and the commands are described in the
77 SPC-4 and earlier SPC-3 and SPC-2 standards. The SPC-4 standard (ANSI
78 INCITS 513-2015) added the XCOPY(LID4) sub-family of copy offloaded
79 commands. Now SPC-5 drafts have dropped the LID1 variants and removed
80 the LID4 suffix on the remaining XCOPY family of commands. To differen‐
81 tiate, this man page will continue to use the LID1 and LID4 suffixes.
82 There is a subset of XCOPY(LID4), specialized for offloaded disk to
83 disk copies, that is known by the market name: ODX. In the descriptions
84 below "xcopy" refers to copies based on XCOPY(LID1) while "odx" refers
85 to either full or partial ODX copies. See the XCOPY and ODX sections
86 below for more information.
87 The syntax of the dd command is somewhat unique in Unix and ddpt fol‐
89 lows in a similar fashion. Operands (i.e. those with the <name>=<some‐
90 thing> structure) are shown in OPERANDS section. The more familiar Unix
91 options (i.e. those starting with one or two hyphens) are shown in the
92 OPTIONS section. Then there are a few arguments which are command line
93 entities that are neither operands nor options, see the ARGUMENTS sec‐
94 tion.
95
97 The operands are listed alphabetically (by <name>) below. The <name> is
98 the part that is to the left of the equal sign. All <names> start with
99 a lower case alphabetical character.
100 bpt=BPT[,OBPC]
102 where BPT is Blocks Per Transfer. A direct copy is made up of
103 multiple transfers, each first reading BPT input blocks (i.e.
104 BPT * IBS bytes) from IFILE into the copy buffer and then from
105 that copy buffer writing (BPT * IBS) / OBS output blocks to
106 OFILE. This continues until the copy is finished, with the last
107 transfer being potentially shorter. The default BPT value varies
108 depending on IBS. When IBS < 8, BPT is 8192; when IBS < 64, BPT
109 is 1024; when IBS < 1024, BPT is 128; when IBS < 8192, BPT is
110 16; when IBS < 32768, BPT is 4; else BPT defaults to 1. If BPT
111 is given as 0 it is treated as the default value. For "bs=512",
112 BPT defaults to 128 so that 64 KiB (or less) is read from IFILE
113 into the copy buffer. This operand is treated differently in ODX
114 and is typically only needed for testing; see ODX section.
115 The optional OBPC (Output Blocks Per Check) argument controls
116 the granularity of sparse writes, write sparing and trim checks.
117 The default granularity is the size of the copy buffer (i.e. BPT
118 * IBS bytes). That can be reduced by specifying OBPC. The finest
119 granularity is when OBPC is 1 which implies the unit of each
120 check is OBS bytes. When OBPC is 0, or not given, the default
121 granularity is used. Large OBPC values are rounded down so that
122 OBPC*OBS does not exceed the size of the copy buffer.
123 odx: may be used to limit the data represented by each ROD.
124 Mainly for testing.
125 If BPT is too large on Linux, the obscure "Invalid argument" er‐
126 ror value (EINVAL) is returned.
127 bs=BS where BS is the IFILE and OFILE block size in bytes. Conflicts
129 with either the "ibs=" or "obs=" operands. The value of BS is
130 placed in IBS and OBS. If IFILE or OFILE is a "pt" device then
131 BS must be the logical block size of the device. See the DD DIF‐
132 FERENCES section below. The default is 512 bytes unless overrid‐
133 den by the DDPT_DEF_BS environment variable. Note that newer
134 disks use 4096 byte blocks with perhaps larger block sizes com‐
135 ing in the future. CD/DVD/BD media use a logical block size of
136 2048 bytes.
137 cdbsz=IO_CDBSZ
139 size of SCSI READ and/or WRITE (VERIFY) command descriptor
140 blocks (cdb) in bytes. IO_CDBSZ may be one number or two numbers
141 separated by a comma. The acceptable numbers are 0, 6, 10, 12,
142 16 or 32. The default 0 will usually be set to 10 internally un‐
143 less the (first and last) LBAs cannot fit in 32 bits in which
144 case the 16 byte variant of each command is used. If one number
145 is given it applies both to the IFILE and IFILE. If two numbers
146 are given, the first applies to the IFILE (i.e. the READ com‐
147 mand) and the second applies to the OFILE.
148 If IFILE or OFILE is not a SCSI pass-through device then the
149 corresponding IO_CDBSZ value is ignored.
150 cdl=CDL
152 allows setting of command duration limits. CDL is either a sin‐
153 gle value or two values separated by a comma. If one value is
154 given, it applies to both IFILE and OFILE (if they are
155 pass-through devices). If two values are given, the first ap‐
156 plies to IFILE while the second applies to OFILE. The value may
157 be from 0 to 7 where 0 is the default and means there are no
158 command duration limits. Command duration limits are only sup‐
159 ported by 16 and 32 byte READ and WRITE commands (and the WRITE
160 SCATTERED command which is not used by this utility). If the
161 cdbsz operand is not given and would have a value less than 16,
162 then if CDL is greater than 0, the cdbsz is increased to 16.
163 Command duration limits can be accesses and changed in the Com‐
164 mand duration limit A and B mode pages, plus the Command dura‐
165 tion limit T2A and T2B mode pages. The sdparm utility may be
166 used to access and change these mode pages.
167 coe={0|1}
169 set to 1 for continue on error. Applies to errors on input and
170 output for pt devices but only on input from block devices or
171 regular files. Errors on other files will stop ddpt. Default is
172 0 which implies stop on any error. See the 'coe' flag for more
173 information.
174 coe_limit=CL
176 where CL is the maximum number of consecutive bad blocks stepped
177 over due to "coe=1" on reads before the copy terminates. The de‐
178 fault is 0 which is implies no limit. This operand is meant to
179 stop the copy soon after unrecorded media is detected while
180 still offering "continue on error" capability for infrequent,
181 randomly distributed errors.
182 conv=CONVS
184 see the CONVERSIONS section below.
185 count=COUNT
187 copy COUNT input blocks from IFILE to OFILE. If this operand is
188 not given (or COUNT is '-1') then the COUNT may be deduced from
189 either IFILE or OFILE. See the COUNT section below.
190 If a 'hard' gather list is given to skip=SKIP or a 'hard' scat‐
191 ter list is given to seek=SEEK then typically count=COUNT should
192 not be supplied. This is because a 'hard' scatter gather list
193 implies a transfer count. If both are given then ddpt will exit
194 if they are unequal, the force flag can be used to override this
195 action. See the SCATTER GATHER LISTS section below for a discus‐
196 sion of 'hard' and 'soft' scatter gather lists.
197 ddpt=VERS
199 causes a syntax error while parsing the command line if the cur‐
200 rent version of the ddpt utility is less than VERS. VERS can
201 take one of two forms: starting with a digit in which case is
202 should have the form "<major_vn>.<minor_vn>" or starting with
203 the letter "r" followed by "<svn.rev>". The latter case is the
204 subversion revision number. Both numbers can be found in the
205 output of the --version option. The purpose of this operand is
206 to be placed in job files so that they are not run on older ver‐
207 sions of this utility
208 delay=MS[,W_MS]
210 after each segment is copied (typically every (IBS * BPT) bytes)
211 a delay (sleep) of MS milliseconds is performed. The default
212 value for MS is 0 which implies no delay. If W_MS is given and
213 greater than 0 (its default value) then there is an additional
214 delay of W_MS milliseconds associated with each actual write op‐
215 eration that is performed. If MS is greater than 0 then there
216 is not a delay before the first copy segment (or after the
217 last); if W_MS is greater than 0 then there is not a delay be‐
218 fore the first write segment. These delays can be used for a
219 bandwidth limiting.
220 odx: the MS delay is implemented in the same fashion after each
221 ROD is copied, apart from the last. If W_MS is greater than 0
222 then that delay occurs before each WUT command, apart from the
223 first.
224 ibs=IBS
226 where IBS is the IFILE block size in bytes. The default value is
227 BS or its default (512). Conflicts the "bs=" operand (i.e. giv‐
228 ing both "bs=512 ibs=512" is considered a syntax error).
229 id_usage=LIU
231 xcopy: SCSI EXTENDED COPY parameter list LIST ID USAGE field is
232 set to LIU. The default value is 0 or 2 . LIU can be a number
233 between 0 and 3 inclusive or a string. The strings can be ei‐
234 ther: 'hold' for 0, 'discard' for 2 or 'disable' for 3.
235 if=IFILE
237 read from IFILE. If IFILE is '-' then stdin is read. Starts
238 reading at the beginning of IFILE unless SKIP is given.
239 This operand must be given (apart from one odx case and when
240 iflag=00 or iflag=ff is given).
241 odx: the rtf=RTF operand may replace the if=IFILE operand as in‐
242 put. See the ODX section.
243 iflag=FLAGS
245 where FLAGS is a comma separated list of one or more flags out‐
246 lined in the FLAGS section below. These flags are associated
247 with IFILE and are mostly ignored when IFILE is stdin.
248 intio={0|1}
250 set to 1 for allow signals (SIGINT, SIGPIPE and SIGUSR1 (or SIG‐
251 INFO)) to be received during IO from IFILE or IO to OFILE or
252 OFILE2. Default is 0 which causes these signals to be masked
253 during IO operations with a check for signals prior each IO. As
254 long as IO operations don't lock up (e.g. SCSI READ and WRITE
255 commands) the default is the safer option. Even if IO operations
256 do lock up it is best to let the kernel take care of that.
257 iseek=SKIP
259 in its simplest form, SKIP is a single number: start reading af‐
260 ter SKIP blocks (each of IBS bytes) from the start of IFILE.
261 Default is block 0 (i.e. start of file). This operand is a syn‐
262 onym for skip=SKIP, see its description.
263 ito=ITO
265 odx: ITO is the inactivity timeout whose units are seconds. The
266 default value is 0 which means the copy manager will take the
267 default inactivity timeout value from the Block Device ROD Token
268 Limits descriptor in the Third Party Copy VPD page. ITO is ig‐
269 nored if it it exceeds the maximum inactivity timeout value in
270 the same descriptor (unless the force flag is given).
271 list_id=LID
273 LID is the xcopy LIST IDENTIFIER field or the STR_ID field for
274 the WRITE STREAM command. Fo xcopy it is used to associate an
275 originating xcopy command with follow-up commands such as RE‐
276 CEIVE ROD TOKEN INFORMATION. If given, the LID should not clash
277 with any other xcopy LID currently in use on this I_T nexus.
278 xcopy: LID is a 1 byte (8 bit) value whose default value is 1
279 or, if id_usage=disable, 0 . LID must not exceed 255.
280 odx: LID is a 4 byte (32 bit) value whose default value is 257
281 (i.e. 0x101) and, if a second default is needed, 258 (0x102) is
282 used. If a clash is detected on the default list identifier
283 value then the next higher value is tried (stopping after 10 at‐
284 tempts).
285 oflag=wstream: LID is a 2 byte (16 bit) value whose default
286 value is 0. It is the Stream Identifier (STR_ID field) for the
287 WRITE STREAM(16) command. Valid Stream identifiers are 0x1 to
288 0xffff (65535) inclusive, so the default value of 0 is invalid.
289 obs=OBS
291 where OBS is the OFILE block size in bytes. The default value is
292 BS or its default (512). Conflicts the "bs=" operand (e.g. giv‐
293 ing both "bs=512 obs=512" is considered a syntax error). If OBS
294 is given then it has the following restriction: the integer ex‐
295 pression (((IBS * BPT) % OBS) == 0) must be true. Stated an‐
296 other way: the copy buffer size must be an integral multiple of
297 OBS. If of2=OFILE2 is given then OBS is its block size as well.
298 of=OFILE
300 write to OFILE. The default value is /dev/null . If OFILE is '-'
301 then writes to stdout. If OFILE is /dev/null then no actual
302 writes are performed. If OFILE is '.' (period) then it is
303 treated the same way as /dev/null . If OFILE exists then it is
304 _not_ truncated unless "oflag=trunc" is given. See section on DD
305 DIFFERENCES.
306 odx: if this operand (of=OFILE) is not given and the rtf=RTF op‐
307 erand is given then the RTF file may be thought of as receiving
308 the output in the form of one or more ROD Tokens. See the ODX
309 section.
310 of2=OFILE2
312 write output to OFILE2. The default action is not to do this ad‐
313 ditional write (i.e. when this operand is not given). OFILE2 is
314 assumed to be a regular file or a fifo (i.e. a named pipe).
315 OFILE2 is opened for writing and is created if necessary. If
316 OFILE2 is a fifo (named pipe) then some other command should be
317 consuming that data (e.g. 'md5sum OFILE2'), otherwise this util‐
318 ity will block. The write to OFILE2 occurs before the write to
319 OFILE and prior to sparse writing and write sparing logic. So
320 everything read is written to OFILE2.
321 OFILE2 is not truncated before writing. Assuming that the OFILE2
322 length is shorter than what is written (or it is created) then
323 its contents should be the concatenation of all segments (each
324 of ibs*bpt bytes long, with the last segment being possibly
325 shorter). The gather list given to skip=SKIP effects what is
326 read into each segment so it indirectly effects what is written
327 to OFILE2. However the scatter list given to seek=SEEK has no
328 effect on what is written to OFILE2.
329 oflag=FLAGS
331 where FLAGS is a comma separated list of one or more flags out‐
332 lined in the FLAGS section. These flags are associated with
333 OFILE and are ignored when OFILE is /dev/null, '.' (period), or
334 stdout.
335 oseek=SEEK
337 start writing SEEK blocks (each of OBS bytes) from the start of
338 OFILE. Default is block 0 (i.e. start of file). This operand is
339 a synonym for seek=SEEK, see its description.
340 prio=PRIO
342 xcopy: SCSI EXTENDED COPY parameter list PRIORITY field is set
343 to PRIO. The default value is 1 .
344 protect=RDP[,WRP]
346 where RDP is the RDPROTECT field in SCSI READ commands and WRP
347 is the WRPROTECT field in SCSI WRITE commands. The default value
348 for both is 0 which implies no additional protection information
349 will be transferred. Both RDP and WRP can be from 0 to 7. If
350 RDP is greater than 0 then IFILE must be a pt device. If WRP is
351 greater than 0 then OFILE must be a pt device.
352 When copying data plus protection information from one disk to
353 another then 'protect=3,3' will give the least number of prob‐
354 lems as that combination then of PI checking on both the read
355 and write side. See the PROTECTIO INFORMATION section below.
356 retries=RETR
358 sometimes retries at the host are useful, for example when there
359 is a transport error. When RETR is greater than zero then SCSI
360 READs and WRITEs are retried on error, RETR times. Default value
361 is zero. Only applies to errors on pt devices.
362 rtf=RTF
364 odx: where RTF is a filename. One or more ROD tokens are written
365 to RTF during a read to tokens variant or a full copy variant.
366 One or more ROD tokens are read from RTF during a write from to‐
367 ken variant. This operand is not required on a full copy vari‐
368 ant. ROD Tokens are 512 bytes long and an extra 8 byte (big-en‐
369 dian) integer containing the 'number of bytes represented' is
370 placed after each ROD Token if rtf_len is given.
371 rtype=RTYPE
373 odx: where RTYPE is the ROD Type. The default value (0) indi‐
374 cates that the copy manager (in the source) decides. RTYPE can
375 be a decimal number, a hex number (prefixed by 0x or with a "h"
376 appended) or one of "pit-def", "pit-vuln", "pit-pers",
377 "pit-cow", "pit-any" or "zero". The final truncated word can be
378 spelt out (e.g. "pit-vulnerable"). The "pit-" prefix is a
379 shortening of "point in time" copy. The "zero" causes a special
380 Block device zero Token to be created.
381 seek=SEEK
383 start writing SEEK blocks (each of OBS bytes) from the start of
384 OFILE. Default is block 0 (i.e. start of file). The SEEK value
385 may exceed the number of OBS-sized blocks in OFILE.
386 SEEK can be a scatter (gather) list: see the SCATTER GATHER
387 LISTS section below.
388 skip=SKIP
390 start reading SKIP blocks (each of IBS bytes) from the start of
391 IFILE. Default is block 0 (i.e. start of file). The SKIP value
392 must be less than the number of IBS-sized blocks in IFILE.
393 SKIP can be a (scatter) gather list: see the SCATTER GATHER
394 LISTS section below.
395 status=STAT
397 the STAT value of 'noxfer' suppresses the throughput speed and
398 the copy time reporting at the end of the copy. A STAT value of
399 'none' additionally suppresses the records in and out reporting
400 after the copy. So 'status=none' makes ddpt act like a tradi‐
401 tional Unix command in which "no news is good news". The de‐
402 fault action of ddpt is to show the throughput (in megabytes per
403 second) and the time taken to do the copy after the "records in"
404 and "records out" lines at the end of the copy. A STAT value of
405 'sgl' together with '-vv' option will print internally generated
406 scatter gather lists before the copy begins. When the '-vv' op‐
407 tions is given alone then internal scatter lists headers are
408 printed, but not individual elements. In most cases these scat‐
409 ter gather lists will be the same lists given to the seek=SEEK
410 and skip=SKIP operands. As a convenience the value 'null' is
411 accepted for STAT and does nothing.
412 A STAT value of 'progress' prints a progress report (to stderr)
413 every two minutes. If 'progress' is used twice, either by re‐
414 peating the 'status=progress' operand or by entering 'sta‐
415 tus=progress,progress', then a progress report is printed every
416 minute. If it is used thrice, the a progress report is printed
417 every 30 seconds. Note that care is taken not to flood the OS
418 with calls to check the time which would slow down the copy
419 process. The amount of data output by the progress reports can
420 modified at runtime (e.g. during a long copy). If the verbose
421 flag is 0 or 1 (but not higher and not if the --quiet option is
422 given) then sending a SIG_USR1 (or SIGINFO in FreeBSD) signal to
423 the running ddpt process will toggle the verbose flag between 0
424 and 1. Note there is now a shorter form, the command line op‐
425 tion: --progress or simply '-p'.
426 Note that GNU's dd supports 'noxfer', 'none' and 'progress' with
427 similar semantics.
428 to=TO odx, xcopy: where TO is am xcopy originating command timeout in
430 seconds. The default value is 0 which is converted internally
431 to 600 seconds (10 minutes). Best to set this timeout value well
432 above the expected copy time. In a odx full copy this timeout
433 is applied to both the POPULATE TOKEN and WRITE USING TOKEN com‐
434 mands.
435 verbose=VERB
437 as VERB increases so does the amount of debug reporting sent to
438 stderr. Default value is zero which yields the minimum amount
439 of debug reporting. A value of 1 reports extra information that
440 is not repetitive. A value 2 reports cdbs and responses for SCSI
441 commands that are not repetitive (i.e. other that READ and
442 WRITE). Error processing is not considered repetitive. Values of
443 3 and 4 yield reporting for all SCSI commands, plus Unix read()
444 and write() calls, so there can be a lot of output.
445 If VERB is "-1" then reporting that would have been sent to
446 stderr is redirected to /dev/null essentially throwing it away.
447 It has the same action as the --quiet option.
448 In some cases the position of verbose=VERB (or --verbose) on the
449 command line is significant. For example to debug (or at least
450 list out) a scatter gather list given to skip=SKIP or seek=SEEK
451 the verbose=VERB operand (or --verbose) should appear before
452 skip and/or seek.
453
455 Options are listed in alphabetical order, sorted by their long name.
456 -d, --dry-run
458 does all the operand and option processing, opens given file and
459 devices but bypasses the copy stage. For complex command line
460 invocations or for testing invocations to be placed in script
461 files, this option may be useful to check for syntax and related
462 errors.
463 When used once the logic bypasses the copy just before it would
464 normally start copying. When used twice (or more) it goes deeper
465 into the copy to the IO call level before bypassing the calls.
466 To see (on stderr) information for each IO this option combina‐
467 tion may be useful: '-ddvv'.
468 -f, --flexible
470 this option currently only effects the parsing of sgl_s in files
471 that are in hexadecimal plus they have a leading line with 'HEX'
472 in them. Without this option any such line must be invoked with
473 'H@' before the filename; in other words the 'H' in the invoca‐
474 tion needs to match the HEX in the file. With this option a sgl
475 in a file can be invoked with '@' and if a line with HEX is
476 parsed before any LBA,NUM pairs then it switches to hexadecimal
477 mode; so all the parsed LBA,NUM pairs are assumed to be in hexa‐
478 decimal.
479 -h, --help
481 reports usage message then exits.
482 --job=JF
484 where JF is a file name. That file can contain operands and op‐
485 tions listed in this and the previous sections. See the JOB
486 FILES section below.
487 -o, --odx
489 indicates to this utility that one of the four odx variants is
490 requested. See ODX section.
491 -P, --prefetch
493 this option is only active when the --verify option is also
494 given. It causes the SCSI PRE-FETCH(OFILE, IMMED) command to be
495 sent at the start of each copy segment. See the VERIFY section
496 below.
497 -p, --progress
499 this option has the same effect as status=progress but is
500 shorter to type and easier to remember. When given once, the de‐
501 fault reporting period is two minutes, if given twice (e.g.
502 '-pp') that period is shortened to one minute.
503 -q, --quiet
505 redirects the messages (sent to stderr) to /dev/null which is
506 essentially throwing them away. That redirect takes place after
507 the command line operands and options are parsed and associated
508 sanity checks performed.
509 -v, --verbose
511 equivalent of verbose=1. If --verbose appears twice then that is
512 equivalent to verbose=2. Also -vv is equivalent to verbose=2.
513 -X, --verify
515 rather than copy, a comparison is done between IFILE and OFILE.
516 The compare continues until an inequality is found at which
517 point the operation stops. This is only available if OFILE is a
518 pass-through device that implements VERIFY(10 or 16) with BYTCHK
519 set to 1. See the VERIFY section below.
520 -V, --version
522 reports version number information then exits.
523 -w, --wscan
525 this option is available in Windows only. It lists storage de‐
526 vice names and the corresponding volumes, if any. When used
527 twice it adds the "bus type" of the closest transport (e.g. a
528 SATA disk in a USB connected enclosure has bus type USB). When
529 used three times a SCSI adapter scan is added. When used four
530 times only a SCSI adapter scan is shown. See EXAMPLES section
531 below and the README.win32 file.
532 -x, --xcopy
534 this option will attempt to call the SCSI EXTENDED COPY(LID1)
535 command. In the absence of another indication the xcopy command
536 will be sent to the destination (i.e. OFILE). See the section on
537 ENVIRONMENT VARIABLES below.
538
540 Arguments do not start with hyphen nor contain a "=".
541 ddpt this string is just a marker. It must not appear in the command
543 line and it must appear in the contents of a job file that isn't
544 part of a comment (i.e. following a "#" on a line). A syntax er‐
545 ror is generated (and no copy occurs) if these rules are vio‐
546 lated.
547 JF a command line element that does not contain a '=' (i.e. a ddpt
549 operand) and does not start with '-', apart from the string
550 "ddpt" is treated as a job file (i.e. JF). See the JOB FILES
551 section below.
552
554 One or more conversions can be given to the "conv=" option. If more
555 than one is given, they should be comma separated. ddpt does not per‐
556 form the traditional dd conversions (e.g. ASCII to EBCDIC). Recently
557 added conversions inherited from GNU's dd overlap somewhat with the
558 some of ddpt flags.
559 fdatasync
561 equivalent to "oflag=fdatasync". Flushes data associated with
562 the OFILE to storage at the end of the copy. This conversion is
563 for compatibility with GNU's dd.
564 fsync equivalent to "oflag=fsync". Flushes data and meta-data associ‐
566 ated with the OFILE to storage at the end of the copy. This con‐
567 version
568 no_del_tkn
570 equivalent to "oflag=no_del_tkn".
571 nocreat
573 OFILE will not be created if it doesn't exist. The default ac‐
574 tion if OFILE does not exist is to create a regular file (then
575 write into it). The default action can be surprising if writing
576 to a device node in /dev and due to some external action (e.g. a
577 USB key being removed) that device node name disappears.
578 noerror
580 this conversion is very close to "iflag=coe" and is treated as
581 such. See the "coe" flag. Note that an error on a block device
582 or regular file OFILE will stop the copy.
583 notrunc
585 this conversion is accepted for compatibility with dd and ig‐
586 nored since the default action of this utility is not to trun‐
587 cate OFILE.
588 null has no affect, just a placeholder.
590 prefer_rcs
592 equivalent to "oflag=prefer_rcs".
593 resume See "resume" in the FLAGS sections for more information.
595 rtf_len
597 equivalent to "oflag=rtf_len".
598 sparing
600 See "sparing" in the FLAGS sections for more information.
601 sparse FreeBSD's dd supports "conv=sparse" and now GNU's dd does as
603 well so the same syntax is supported in ddpt. See "sparse" in
604 the FLAGS sections for more information.
605 sync is ignored by ddpt. With dd it means supply zero fill (rather
607 than skip) and is typically used like this "conv=noerror,sync"
608 to have the same functionality as ddpt's "iflag=coe".
609 trunc if OFILE is a regular file then truncate it prior to starting
611 the copy. See "trunc" in the FLAGS section.
612
614 A list of flags and their meanings follow. The flag name is followed by
615 one or two indications in square brackets. The first indication is ei‐
616 ther "[i]", "[o]" or "[io]" indicating this flag is active for the
617 IFILE, OFILE or both the IFILE and the OFILE. The second indication
618 contains some combination of "reg", "blk" "pt", "odx", or "xcopy".
619 These indicate whether the flag applies to a regular file, a block de‐
620 vice (accessed via Unix read() and write() commands, a pass-through de‐
621 vice, an ODX offloaded copy or a XCOPY(LID1) offloaded copy respec‐
622 tively. Other special file types that are sometimes referred to are
623 "fifo" and "tape".
624 00 [i] This flag may replace IFILE with a source of zero (0x0) bytes.
626 If IFILE is given and is shorter than OFILE then it continues to
627 copy after IFILE is exhausted supplying zero fill bytes. Can
628 only be used on input. Zeros can also be generated by using
629 "if=/dev/zero" or an equivalent.
630 If both '00' and 'ff' flags are given then a marching byte pat‐
631 tern is placed in the segment prior to writing it out. It starts
632 at 0x0 and wraps after 0xff (if the segment is large enough, as
633 it usually is).
634 append [o] [reg], [io] [odx]
636 causes the O_APPEND flag to be added to the open of OFILE. For
637 regular files this will lead to data being appended to the end
638 of any existing data. Conflicts the seek=SEEK option. The de‐
639 fault action of this utility is to overwrite any existing data
640 from the beginning of OFILE or, if SEEK is given, starting at
641 block SEEK. Note that attempting to 'append' to a device file
642 (e.g. a disk) will usually be ignored or may cause an error to
643 be reported.
644 odx: if the rtf=RTF option is given, RTF exists, is a regular
645 file and this utility wants to write to RTF then new ROD Tokens
646 are appended to RTF. The default action is to truncate RTF be‐
647 fore new ROD Tokens are written to it.
648 atomic [o] [pt]
650 this flag changes the pass-through SCSI WRITE command to the
651 SCSI WRITE ATOMIC(16) command on OFILE (and the
652 cdbsz={6|10|12|16|32} option is ignored for OFILE). If this flag
653 is applied to IFILE or to a non pass-through file then it is ig‐
654 nored.
655 block [io] [pt]
657 pass-through file opens are non-blocking by default and may re‐
658 port the pt device is busy. Use this flag to open blocking so
659 utility may wait until another process locking (or with an ex‐
660 clusive open) is complete before continuing.
661 bytchk [o] [pt]
663 only active when used together with oflag=wverify. Sets the
664 BYTCHK field in the SCSI WRITE AND VERIFY command. Since that
665 field is two bits wide, this flag can be specified multiple
666 times (up to three) to place the corresponding value in the
667 field.
668 cat [io] [xcopy]
670 xcopy: set CAT (residual data handling) bit in EXTENDED
671 COPY(LID1) parameter list segment descriptor header. May appear
672 in either flag list when xcopy is being used. Works with the PAD
673 bit for handling residual data on the destination side. See the
674 XCOPY section below.
675 coe [io] [pt], [i] [reg,blk]
677 continue on error. 'iflag=coe oflag=coe' and 'coe=1' are equiva‐
678 lent. Errors occurring on output regular or block files will
679 stop ddpt. Error messages are sent to stderr. This flag is sim‐
680 ilar to 'conv=noerror,sync' in the dd(1) utility. Unrecovered
681 errors are counted and reported in the summary at the end of the
682 copy.
683 This paragraph concerns coe on pt devices. A medium, hardware or
685 blank check error during a read operation will will cause the
686 following: first re-read blocks prior to the bad block, then try
687 to recover the bad block (supplying zeros if that fails), and
688 finally re-read the blocks after the bad block. A medium, hard‐
689 ware or blank check error while writing is reported but other‐
690 wise ignored. SCSI disks may automatically try and remap faulty
691 sectors (see the AWRE and ARRE in the read write error recovery
692 mode page (the sdparm utility can access these attributes)). If
693 bad LBAs are reported by the pass-through then the LBA of the
694 lowest and highest bad block is also reported.
695 This paragraph concerns coe on input regular files and block de‐
697 vices. When a EIO or EREMOTEIO error is detected on a normal
698 segment read then the segment is re-read one block (i.e. IBS
699 bytes) at a time. Any block that yields a EIO or EREMOTEIO error
700 is replaced by zeros. Any other error, a short read or an end of
701 file will terminate the copy, usually after the data that has
702 been read is written to the output file.
703 dc [io] [blk,pt]
705 xcopy: set DC (destination counter) bit in EXTENDED COPY(LID1)
706 parameter list segment descriptor header. May appear in either
707 flag list when xcopy is being used.
708 direct [io] [reg,blk]
710 causes the O_DIRECT flag to be added to the open of IFILE and/or
711 OFILE. This flag requires some memory alignment on IO. Hence
712 user memory buffers are aligned to the page size. May have no
713 effect on pt devices or cause an error (e.g. Linux seems to
714 dis-allow O_DIRECT on character devices (like sg devices) yield‐
715 ing EINVAL). This flag will bypass caching/buffering normally
716 done by block layer. Beware of data coherency issues if the same
717 locations have been recently accessed via the block layer in its
718 normal mode (i.e. non-direct). See open(2) man page.
719 dpo [io] [pt]
721 set the DPO bit (disable page out) in SCSI READ and WRITE com‐
722 mands. Not supported for 6 byte cdb variants of READ and WRITE.
723 Indicates that data is unlikely to be required to stay in device
724 (e.g. disk) cache. May speed media copy and/or cause a media
725 copy to have less impact on other device users.
726 errblk [i] [pt] [experimental]
728 attempts to create or append to a file called "errblk.txt" in
729 the current directory the logical block addresses of blocks that
730 cannot be read. The first (appended) line is "# start <time‐
731 stamp>". That is followed by the LBAs in hex (and prefixed with
732 "0x") of any block that cannot be read, one LBA per line. If the
733 sense data does not correctly identify the LBA of the first er‐
734 ror in the range it was asked to read then a LBA range is re‐
735 ported in the form of the lowest and the highest LBA in the
736 range separated by a "-". At the end of the copy a line with "#
737 stop <timestamp>" is appended to "errblk.txt". Typically used
738 with "coe".
739 excl [io] [reg,blk]
741 causes the O_EXCL flag to be added to the open of IFILE and/or
742 OFILE. See open(2) man page.
743 fdatasync [o] [reg,blk]
745 Flushes data associated with the OFILE to storage at the end of
746 the copy.
747 ff [i] This flag may replace IFILE with a source of 0xff bytes. If
749 IFILE is given and is shorter than OFILE then it continues to
750 copy after IFILE is exhausted supplying 0xff fill bytes. Can
751 only be used on input.
752 If both '00' and 'ff' flags are given then a marching byte pat‐
753 tern is placed in the segment prior to writing it out. It starts
754 at 0x0 and wraps after 0xff (if the segment is large enough, as
755 it usually is).
756 flock [io] [reg,blk,pt]
758 after opening the associated file (i.e. IFILE and/or OFILE) an
759 attempt is made to get an advisory exclusive lock with the
760 flock() system call. The flock arguments are "FLOCK_EX |
761 FLOCK_NB" which will cause the lock to be taken if available
762 else a "temporarily unavailable" error is generated. An exit
763 status of 90 is produced in the latter case and no copy is done.
764 See flock(2) man page.
765 force [io] [pt] [xcopy,odx]
767 override difference between given block size and the block size
768 found by the SCSI READ CAPACITY command. Use the given block
769 size. Without this flag the copy would not be performed. pt ac‐
770 cess to what appears to be a block partition is aborted in ver‐
771 sion 0.92; that can be overridden by the force flag. For related
772 reasons the 'norcap' flag requires this flag when applied to a
773 block device accessed via pt.
774 xcopy and odx: various limits imposed by associated VPD pages or
775 the RECEIVE COPY OPERATING PARAMETERS command can be overridden
776 (i.e. exceeded) if this flag is given. Note that the copy man‐
777 ager will probably object.
778 fsync [o] [reg,blk]
780 Flushes data and metadata (describing the file) associated with
781 the OFILE to storage at the end of the copy.
782 fua [io] [pt]
784 causes the FUA (force unit access) bit to be set in SCSI READ
785 and/or WRITE commands. The 6 byte variants of the SCSI READ and
786 WRITE commands do not support the FUA bit.
787 fua_nv [io] [pt]
789 causes the FUA_NV (force unit access non-volatile cache) bit to
790 be set in SCSI READ and/or WRITE commands. This only has an ef‐
791 fect with pt devices. The 6 byte variants of the SCSI READ and
792 WRITE commands do not support the FUA_NV bit. The FUA_NV bit was
793 made obsolete in SBC-3 revision 35d.
794 ignoreew [o] [tape]
796 ignore the early warning indication (of end of tape) when writ‐
797 ing to tape. See TAPE section.
798 immed [io] [odx]
800 sets the IMMED bit in the POPULATE TOKEN (when [i]) or WRITE US‐
801 ING TOKEN (when [o]) command. That command should return status
802 promptly after starting the data transfer. The RECEIVE ROD TOKEN
803 INFORMATION command is then used to poll for completion. SCSI
804 command timeouts should not be exceeded, even for very large
805 RODs, if this flag is used.
806 nocache [io] [reg,blk]
808 use posix_fadvise(POSIX_FADV_DONTNEED) to advise corresponding
809 file there is no need to fill the file buffer with recently read
810 or written blocks. If used with "iflag=" it will increase the
811 read ahead on IFILE.
812 no_del_tkn [o] [odx]
814 will clear the DEL_TKN bit on the last WRITE USING TOKEN command
815 of each ROD Token in a odx full copy. In a large odx full copy
816 several ROD Tokens may be used (one after the other). The de‐
817 fault action is to set the DEL_TKN bit on the last WUT command
818 of each ROD. Either way it should not make much difference be‐
819 cause the copy manager deletes a ROD Token when its inactivity
820 time-out occurs.
821 nocreat [o]
823 if OFILE does not exist then an error will be generated rather
824 than creating an empty regular file. This flag has the same ac‐
825 tion as "conv=nocreat".
826 nofm [o] [tape]
828 no File Mark (FM) on close when writing to tape. See TAPE sec‐
829 tion.
830 nopad [o] [tape]
832 when the block to be written to a tape drive contains less than
833 OBS bytes, then this option causes the partial block to be writ‐
834 ten as is. The default action for a tape in this case is to pad
835 the block. See TAPE section.
836 norcap [io] [pt]
838 do not perform SCSI READ CAPACITY command on the corresponding
839 pt device. If used on block device accessed via pt then 'force'
840 flag is also required. This is to warn about using pt access on
841 what may be a block device partition.
842 nowrite [o] [reg,blk,pt]
844 bypass writes to OFILE. The "records out" count is not incre‐
845 mented. OFILE is still opened but "oflag=trunc" if given is ig‐
846 nored. Also the ftruncate call associated with the sparse flag
847 is ignored (i.e. bypassed). Commands such as trim and SCSI SYN‐
848 CHRONIZE CACHE are still sent.
849 null [io]
851 has no affect, just a placeholder.
852 odx [io] [odx]
854 indicates to this utility that one of the four variants of an
855 odx copy is requested. Using any of the --odx, rtf=RTF or
856 rtype=RTYPE options also indicates that odx is requested. See
857 the ODX section.
858 pad [o] [reg,blk,pt], [io] [xcopy]
860 when the block to be written (typically the last block) contains
861 less than OBS bytes, then this option causes the block to be
862 padded with zeros (i.e. bytes of binary zero). The default ac‐
863 tion for a regular file and a fifo is to do a partial write. The
864 default action of a block and a pt device is to ignore the par‐
865 tial write. The default action of a tape is to pad, so this flag
866 is not needed (see the nopad flag).
867 xcopy: sets the PAD bit in the CSCD descriptor of the associated
868 IFILE or OFILE. Is associated with residual data handling and
869 works together with the cat flag. See the XCOPY section below.
870 prealloc [o] [reg]
872 use the fallocate() call prior to starting a copy to set OFILE
873 to its expected size.
874 prefer_rcs [o] [odx]
876 prefer RECEIVE COPY STATUS (RCS) command to the RECEIVE ROD TO‐
877 KEN INFORMATION (RRTI) command which is the default. This only
878 is active when polling after a WUT command (since polling after
879 a PT command needs to fetch the ROD Token so it needs the RRTI
880 command).
881 pt [io] [blk,pt]
883 causes a device to be accessed in "pt" mode. In "pt" mode SCSI
884 READ and WRITE commands are sent to access blocks rather than
885 standard UNIX read() and write() commands. The "pt" mode may be
886 implicit if the device is only capable of passing through SCSI
887 commands (e.g. the /dev/sg* and some /dev/bsg/* devices in
888 Linux). This flag is needed for device nodes that can be ac‐
889 cessed both via standard UNIX read() and write() commands as
890 well as SCSI commands. Such devices default standard UNIX read()
891 and write() commands in the absence of this flag.
892 rarc [i] [pt]
894 bit set in READ(10, 12, 16 and 32) to suppress RAID rebuild
895 functions when a bad (or recovered after difficulties) block is
896 detected.
897 resume [o] [reg]
899 when a copy is interrupted (e.g. with Control-C from the key‐
900 board) then using the same invocation again with the addition of
901 "oflag=resume" will attempt to restart the copy from the point
902 of the interrupt (or just before that point). It is harmless to
903 use "oflag=resume" when OFILE doesn't exist or is zero length.
904 If the length of OFILE is greater than or equal to the length
905 implied by a ddpt invocation that includes "oflag=resume" then
906 no further data is copied.
907 self [io] [pt]
909 used together with trim flag to do a self trim (trim of segments
910 of a pt device that contain all zeros). If OFILE is not given,
911 then it is set to the same as IFILE. If SEEK is not given it set
912 to the same value as SKIP (possibly adjusted if IBS and OBS are
913 different). Implicitly sets "nowrite" flag.
914 sparing [o] [reg,blk,pt]
916 during the copy each IBS * BPT byte segment is read from IFILE
917 into a buffer. Then, instead of writing that buffer to OFILE,
918 the corresponding segment is read from OFILE into another buf‐
919 fer. If the two buffers are different, the former buffer is
920 written to the OFILE. If the two buffers compare equal then the
921 write to OFILE is not performed. Write sparing is useful when a
922 write operation is significantly slower than a read. Under some
923 conditions flash memory devices have slow writes plus an upper
924 limit on the number of times the same cell can be rewritten. The
925 granularity of the comparison can be reduced from the default
926 IBS * BPT byte segment with the the OBPC value given to the
927 "bpt=" option. The finest granularity is when OBPC is 1 which
928 implies OBS bytes.
929 sparse [io] [reg,blk,pt]
931 after each IBS * BPT byte segment is read from IFILE, it is
932 checked to see if it is all zeros. If so, that segment is not
933 written to OFILE. See the section on SPARSE WRITES below for the
934 difference between using this flag once or twice. The granular‐
935 ity of the zero comparison can be reduced from the default IBS *
936 BPT byte segment with the OBPC value given to the "bpt=" option.
937 The sparse flag may be used on input when a file is only being
938 read (e.g. when of=OFILE is not given or OFILE is /dev/null) to
939 determine how many blocks are contained in sparse segments of
940 IFILE.
941 ssync [o] [pt]
943 if OFILE is in "pt" mode then the SCSI SYNCHRONIZE CACHE command
944 is sent to OFILE at the end of the copy.
945 strunc [o] [reg]
947 perform a sparse copy with a ftruncate system call to extend the
948 length of the OFILE if required. Sets the sparse flag internally
949 if this has not been specified on the command line. See the
950 sparse flag and the section on SPARSE WRITES below.
951 sync [io] [reg,blk]
953 causes the O_SYNC flag to be added to the open of IFILE and/or
954 OFILE. See open(2) man page.
955 rtf_len [io] [odx]
957 odx: with the 'read to tokens' variant, after 512 bytes of each
958 ROD Token are written to RTF an additional 8 byte (big endian)
959 integer is written. That integer is the number of bytes that the
960 associated ROD represents. The draft standards say for standard
961 ROD types the ROD Token contains this value. However vendor spe‐
962 cific ROD types may be used or vendors may choose not to comply.
963 Either way the 'write from tokens' variant needs to know the
964 data size associated with the ROD it is writing from.
965 trim [io] [pt] [experimental]
967 similar logic to the "sparse" option. However instead of skip‐
968 ping segments that are full of zeros a "trim" command is sent to
969 OFILE. Usually set as an oflag argument but for self trim can be
970 used as an iflag argument (e.g. "iflag=self,trim"). Depending on
971 the usage this may require the device to support "deterministic
972 read zero after trim". See the TRIM, UNMAP AND WRITE SAME sec‐
973 tion below.
974 trunc [o] [reg]
976 if OFILE is a regular file then it is truncated prior to start‐
977 ing the copy. If SEEK is not given or 0 then OFILE is truncated
978 to zero length; when SEEK is larger than zero the truncation
979 takes place at file byte pointer SEEK*OBS. Ignored if
980 "oflag=append". Conflicts with "oflag=sparing".
981 unmap [io] [pt]
983 same as the trim flag.
984 wverify [o] [pt]
986 this causes SCSI WRITE AND VERIFY commands to be sent to OFILE
987 (instead of SCSI WRITE (or WRITE ATOMIC) commands). Note that
988 the fua flag is ignored when this flag is given. The BYTCHK
989 field in the SCSI WRITE AND VERIFY commands is set to zero un‐
990 less the bytchk flag is also given.
991 wstream [o] [pt]
993 this causes SCSI WRITE STREAM(16) command to be sent to OFILE
994 (instead of SCSI WRITE. The Stream Identify (valid range: 1 to
995 0xffff (65535)) should be given via the list_id=LID operand
996 (note that it defaults to 0 which is invalid). The stream can be
997 created (closed (for write) or its status checked) with the
998 sg_stream_ctl utility. It is the user's responsibility to open a
999 stream before calling "ddpt ... oflag=wstream list_id=<strm_id>"
1000 and close it after, if required.
1001 xcopy [io] [pt]
1003 invoke SCSI XCOPY(LID1) logic and send the XCOPY command to the
1004 either IFILE or OFILE depending on which flag this called. If
1005 both are given (i.e. an invocation including 'iflag=xcopy
1006 oflag=xcopy') then send the XCOPY(LID1) to OFILE.
1007
1009 When the count=COUNT option is not given (or COUNT is '-1') then an at‐
1010 tempt is made to deduce COUNT as follows.
1011 When both or either IFILE and OFILE are block devices, then the minimum
1013 size, expressed in units of input blocks, is used. When both or either
1014 IFILE and OFILE are pass-through devices, then the minimum size, ex‐
1015 pressed in units of input blocks, is used.
1016 If a regular file is used as input, its size, expressed in units of in‐
1018 put blocks (and rounded up if necessary) is used. Note that the round‐
1019 ing up of the deduced COUNT may result in a partial read of the last
1020 input block and a corresponding partial write to OFILE if it is a regu‐
1021 lar file. After a regular file to regular file copy the length of OFILE
1022 will be the same as IFILE unless OFILE existed and its length was al‐
1023 ready greater than that of IFILE. To get a copy like the standard Unix
1024 cp command, use oflag=trunc with ddpt.
1025 The size of pt devices is deduced from the SCSI READ CAPACITY command.
1027 Block device sizes (or their partition sizes) are obtained from the op‐
1028 erating system, if available.
1029 If skip=SKIP or seek=SEEK are given and the COUNT is deduced (i.e. not
1031 explicitly given) then that size is scaled back so that the copy will
1032 not overrun the file or device.
1033 If COUNT is not given and IFILE is a fifo (and stdin is treated as a
1035 fifo) then IFILE is read until an EOF is detected. If COUNT is not
1036 given and IFILE is a /dev/zero (or equivalent) then zeros are read un‐
1037 til an error occurs (e.g. file system full).
1038 If COUNT is not given and cannot be deduced then an error message is
1040 issued and no copy takes place.
1041
1043 Some operands can have long arguments (e.g. skip=SKIP and iflag=FLAGS)
1044 so that the command line can become quite long. Also scatter gather
1045 lists can be arbitrarily long and may be generated by a program; then
1046 it would be tiresome and error-prone to re-type them on the command
1047 line. So the job file was introduced to hold this utility's operands
1048 and options.
1049 A job file is invoked by either the --job=JF option or by placing the
1051 job filename (JF) unadorned on the command line. The job filename can‐
1052 not contain a "=", start with a hyphen nor be called "ddpt". It is
1053 parsed when it is detected, in a left to right scan of the command
1054 line. The JF file must contain the string "ddpt" and may invoke other
1055 job files (to a maximum depth of 4). A job file should not invoke it‐
1056 self. Also the first line of the job file should not contain any char‐
1057 acters (bytes) with their top bit set; in other words it should be re‐
1058 stricted to 7 bit ASCII (otherwise sanity checks might think it is a
1059 binary file and reject it).
1060 The operands and options within a job file are processed in the order
1062 they are found (i.e. parsing lines left to right, top (of file) to bot‐
1063 tom). The operands and options may contradict (and cause a syntax er‐
1064 ror), override or accumulate with earlier ones, the same as if they ap‐
1065 peared on the command line. For example '-v' on the command line fol‐
1066 lowed by a job file containing '-vv' will result in a verbosity level
1067 of '-vvv' during the copy phase. Empty lines, lines only containing
1068 whitespace(s) and anything from and including a '#' in a job file line
1069 are ignored.
1070
1072 Each element of a scatter gather list (sgl, plural: sgl_s) is made up
1073 of a starting logical block address (LBA, plural: LBAs), and a number
1074 of blocks (NUM) to be accessed from that starting LBA.
1075 The skip=SKIP and seek=SEEK options (and their aliases) can take scat‐
1077 ter gather lists. These can be explicit on the command line, fed in
1078 through stdin or in a file whose name is prefixed by "@" or "H@" on the
1079 command line. For large scatter gather lists, placing them in a file is
1080 the most practical as command lines are limited in length. Scatter
1081 gather list (sgl) is a collective term for either a scatter list or a
1082 gather list. The actual implementation of each sgl is an array. Syn‐
1083 tactically a scatter list and a gather list are the same.
1084 Conceptually these sgl_s refer to what happens at the "far end" (e.g.
1086 within a hard disk or SSD), not what happens in the computer's memory.
1087 So a gather list is associated with the read part of a copy (i.e. the
1088 first half) where a list of Logical Blocks (LBs, identified by their
1089 addresses, hence LBAs) and a number of consecutive, following blocks
1090 are "gathered" from the medium (e.g. a SSD). They are formed into a
1091 linear sequence of bytes that is transferred into a segment in the com‐
1092 puter's RAM. The second half of the copy, the write part, may use a
1093 scatter list. A scatter list starts with a linear sequence of bytes,
1094 taken from the segment, that is transferred to the device and then
1095 "scattered" on the medium as indicated by the list of LBA,NUM pairs.
1096 In the simplest case a sgl is given on the command line and has the
1098 form: LBA1,NUM1[,LBA2,NUM2[,LBA3,NUM3...]]. There must be an even num‐
1099 ber of items (i.e. for every LBAn there should be a following NUMn)
1100 with one exception: when LBA1 alone is given, in which case the value 0
1101 is assumed for NUM1. Comma is the simplest separator for the command
1102 line, but whitespace may also be used (but needs to be escaped because
1103 the shell usually interprets whitespace as an option separator). In a
1104 file (or read from stdin or file redirection) more flexibility is per‐
1105 mitted in the format. The LBA,NUM pairs could all appear on one line
1106 in a file but the line length is limited to 1024 characters (with a
1107 maximum of 256 parseable items on it). So for longer sgl_s one pair per
1108 line is recommended in file format. Also in file format everything
1109 from and including '#' to the end of that line is ignored as are lines
1110 that are empty or only contain whitespace(s).
1111 Each pair becomes one element (or more, see below) of the sgl. By de‐
1113 fault all numbers given for LBA and NUM items are in decimal with op‐
1114 tional suffix multipliers. Hex numbers use either a "0x" prefix or a
1115 'h' suffix (hex notation and suffix multipliers cannot be mixed). In
1116 the case of a 'H@' lead-in to the filename on the command line, all
1117 numbers are interpreted as hex with no suffix multipliers permitted.
1118 Further, with the 'H@' lead-in the file may contain the string 'HEX'
1119 before any numbers are given. The 'HEX' is ignored. The point of this
1120 is to catch when a sgl file with default hexadecimal numbers is given
1121 without the 'H@' lead-in; in this case this utility will exit saying
1122 that file is in the wrong format. This "wrong format" action can be
1123 bypassed with the --flexible option.
1124 Allowing sgl_s brings lots of flexibility (including the possibility to
1126 use the SCSI WRITE SCATTERED command) but with that comes complexity.
1127 Every sgl is scanned to determine if it is monotonic and whether it has
1128 overlapping elements. The term monotonic is used to indicate whether
1129 each LBA is in ascending order, with each LBA greater than the previous
1130 element's LBA. Overlapping refers to the situation when any element's
1131 LBA range intersects with any other element's range. Elements that have
1132 zero number of blocks (described here as "degenerate") are ignored for
1133 determining monotonic and overlapping (and the lowest LBA). Overlapping
1134 elements are not ideal (but not necessarily fatal). The above mentioned
1135 WRITE SCATTERED command allows the medium's logic to write elements in
1136 any order it prefers. That means if elements overlap, then the user
1137 doesn't know which one gets written last (overwriting the one written
1138 to the same LBA earlier). Determining whether element ranges overlap
1139 is difficult in the general case (so this utility doesn't do it) but
1140 easy in the case of a monotonic sgl (so this utility does do it). Warn‐
1141 ings are issued in dangerous situations, with the force flag allowing
1142 the warning to be overridden.
1143 A degenerate sgl element is one that has zero in its NUM field. Nor‐
1145 mally degenerate elements are ignored with some exceptions. The defini‐
1146 tion of the SCSI WRITE SCATTERED command clearly states that degenerate
1147 elements are valid, thus do not cause an error, but cause no associated
1148 action. This utility uses the concept of a 'hard' and 'soft' sgl: a
1149 'soft' sgl is one in which the last element's NUM is zero (i.e. its
1150 last element is degenerate). A sgl with a non-zero NUM in its last ele‐
1151 ment is considered 'hard'. In a 'soft' sgl the LBA of the last element
1152 should be greater than or equal to any LBA+NUM of earlier elements.
1153 Because this is hard to check it is not enforced, so the decision is
1154 made on whether a sgl is hard or soft simply by checking the NUM of
1155 that last element. The difference between a hard and soft sgl is the
1156 way the sum of NUM of all elements is used by this utility. For a
1157 'hard' sgl that sum is used for COUNT when the count=COUNT option is
1158 not given; and if count=COUNT is given and the counts differ then those
1159 two values are output and this utility exits with a syntax error. For a
1160 'soft' sgl the degenerate last element is interpreted as "from the
1161 highest LBA in the list to the end of the copy" where the COUNT is de‐
1162 termined some other way. The "highest LBA" is calculated from all ele‐
1163 ments that have a non-zero number of blocks plus the LBA of the last
1164 element (regardless of whether it is degenerate or not).
1165 The rules in the above paragraph make a one item skip or seek argument
1167 (e.g. skip=0x123) in this utility first become a one element sgl (e.g.
1168 containing the pair [0x123, 0x0]). Since this is the last element, it
1169 is a soft sgl and the transfer will start from the given lba (i.e.
1170 0x123) and continues for the number of blocks indicated by some other
1171 mechanism (e.g. an option such as count=COUNT or the length of IFILE).
1172 This mirrors what the classic dd command does with its skip= and seek=
1173 options.
1174 Some sgl implementation details: LBAs are stored in 64 bit integers
1176 which is more than sufficient to span even the largest disk array be‐
1177 hind a logical device, even if the block size is one byte, which is un‐
1178 likely. The NUM field is a 32 bit integer and this is more problematic.
1179 The reason is that SCSI WRITE commands (and their variants) only allo‐
1180 cate at most a 32 bit integer for this value. Further, modern operating
1181 systems do not allow any driver to get large amounts of contiguous sys‐
1182 tem RAM, even if the machine has it available. A 32 bit integer for NUM
1183 with each block at 512 bytes is around 2 TB of storage. Unix system
1184 calls (in Linux) also limit each read(2) and write(2) system call to 32
1185 bits of single bytes which is 4 GB. The problem for this utility is
1186 that the NUM can easily exceed 32 bits when a single scatter gather
1187 list element refers to the whole device. The action taken by this util‐
1188 ity is to allow larger than 32 bit NUM values to be given on the com‐
1189 mand line (or in a scatter gather list file). However such a large ele‐
1190 ment will be split into multiple elements internally. This will be vis‐
1191 ible to the user when the verbose=VERB option (or one of its variants)
1192 is used with an elevated value.
1193 There is a helper utility called ddpt_sgl in this package for generat‐
1195 ing, manipulating and checking scatter gather lists. See its manpage.
1196
1198 With powerful data tools, the ability to accidentally overwrite and
1199 hence lose important data is ever present. So a significant portion of
1200 the code is dedicated to checking the input arguments for duplications
1201 and contradictions. Still nothing is better than re-reading the command
1202 line (which can be quite long) before hitting the enter key.
1203 Other useful possibilities are to use job files (see the JF argument
1205 and the --job=JF option) and the --dry-run option. The "dry run" op‐
1206 tion is becoming popular in modern command line utilities and more or
1207 less does what the user would expect. Firstly it parses all the command
1208 line arguments then opens IFILE, OFILE and OFILE2 as directed by the
1209 command line and does any meta-data operations that it would typically
1210 do (e.g. check a pass-though or block device's logical block size and
1211 object if it differs from BS, IBS or OBS (whichever applies)). Then
1212 just at the point where the code would commence the actual copy (or
1213 read) it does a premature exit. If the --dry-run option is given twice,
1214 the code continues into the copy logic and bypasses the low level read
1215 and write calls (and file repositioning). That inner level of "dry run"
1216 is useful for debugging and can be used with multiple verbose=VERB op‐
1217 tions.
1218 The verbose=VERB option sends diagnostic messages to stderr. The higher
1220 value of VERB (in verbose=VERB) or the more times that -v is used, the
1221 greater the volume of diagnostic messages. When use three or more times
1222 then diagnostic messages are generated for each read to, and write
1223 from, the working copy buffer; so the volume of messages is propor‐
1224 tional to the number of reads and writes that are done; this can easily
1225 be in the megabyte range. If used less than three times, the reads and
1226 writes associated with the copy do not generate diagnostic messages
1227 (unless abnormal situations are encountered). These diagnostic messages
1228 are mainly associated with command line parsing and fetching meta-data
1229 about the given files, plus messages from the cleanup at the end of the
1230 copy.
1231 The following command line arguments are checked that they don't appear
1233 more than once: bpt=BPT[,OBPC], bs=BS, count=COUNT, ibs=IBS, if=IFILE,
1234 iseek=SKIP, obs=OBS, of=OFILE, of2=OFILE2, oseek=SEEK, seek=SEEK and
1235 skip=SKIP. On the other hand, some arguments are additive, for example
1236 iflag=FLAGS, oflag=FLAGS, status=STAT and --verbose and may appear as
1237 many times as required.
1238
1240 This section describes XCOPY(LID1) support with this utility. For ODX
1241 support (XCOPY(LID4) subset) see the ODX section.
1242 A device (logical unit (LU)) that supports XCOPY operations should set
1244 the 3PC field (3PC stands for Third Party Copy) in its standard INQUIRY
1245 response. That is not checked when this utility does an xcopy operation
1246 but if it fails, that is one thing that the user may want to check.
1247 If the xcopy starts and fails while underway, then 'sg_copy_results -s'
1249 may be useful to view the copy status. It might also be used from a
1250 different process with the same I_T nexus (i.e. the same machine) to
1251 check status during an xcopy operation.
1252 The pad and cat flags control the handling of residual data. As the
1254 data can be specified either in terms of source or target block size
1255 and both might have different block sizes residual data is likely to
1256 happen in these cases. If both block sizes are identical these bits
1257 have no effect as residual data will not occur.
1258 If neither of these flags are set, the EXTENDED COPY command will be
1260 aborted with additional sense 'UNEXPECTED INEXACT SEGMENT'.
1261 If only the cat flag is set the residual data will be retained and made
1263 available for subsequent segment descriptors. Residual data will be
1264 discarded for the last segment descriptor.
1265 If the pad flag is set for the source descriptor only, any residual
1267 data for both source or destination will be discarded.
1268 If the pad flag is set for the target descriptor only any residual
1270 source data will be handled as if the cat flag is set, but any residual
1271 destination data will be padded to make a whole block transfer.
1272 If the pad flag is set for both source and target any residual source
1274 data will be discarded, and any residual destination data will be
1275 padded.
1276 There is a web page discussing ddpt, XCOPY and ODX at
1278 https://sg.danny.cz/sg/ddpt_xcopy_odx.html
1279
1281 This section describes ODX support (an XCOPY(LID4) subset) for this
1282 utility. ODX descriptions use the following command name abbrevia‐
1283 tions: PT for the POPULATE TOKEN command, RRTI for the READ ROD TOKEN
1284 INFORMATION command, and WUT for the WRITE USING TOKEN command.
1285 A device (logical unit (LU)) that supports ODX operations is required
1287 to set the 3PC field (3PC stands for Third Party Copy) in its standard
1288 INQUIRY response and support the Third Party Copy VPD page. If this
1289 utility generates errors noting the absence of these then the device in
1290 question probably does not support ODX.
1291 There a four variants of ODX supported by ddpt:
1293 full copy : ddpt --odx if=/dev/sg3 bs=512 of=/dev/sg4
1294 zero output blocks : ddpt if=/dev/null rtype=zero bs=512 of=/dev/sg4
1295 read to tokens : ddpt if=/dev/sg3 bs=512 skip=@gath.lst rtf=a.rt
1296 write from tokens : ddpt rtf=a.rt bs=512 of=/dev/sg4 seek=@scat.lst
1297 The full copy will call PT and WUT commands repeatedly until the copy
1299 is complete. More precisely the full copy will make the largest single
1300 call to PT allowed by the input's Third Party Copy VPD page (and, if
1301 given, allowed by the BPT argument in the bpt=BPT[,OBPC] option). Then
1302 one or more WUT calls are made to write out from the ROD created by the
1303 PT step. The largest single WUT call is constrained by the output's
1304 Third Party Copy VPD page (and, if given, allowed by the OBPC argument
1305 in the bpt=BPT[,OBPC] option). This sequence continues until the re‐
1306 quested copy is complete.
1307 The zero output blocks variant is a special case of the full copy in
1309 which only WUT calls are made. ODX defines a special ROD Token to zero
1310 blocks. That special ROD Token has a fixed pattern (shown in SBC-3) and
1311 does not need to be created by a PT command like normal ROD Tokens.
1312 The read to tokens and the write from tokens variants are designed to
1314 be the read (input) and write (output) sides respectively of a network
1315 copy. Each can run on different machines by sending the RTF file from
1316 the machine doing the read to the machine doing the write. The read to
1317 tokens will make one or more PT calls and output the resulting ROD To‐
1318 kens to the RTF file. RTF might be a regular file or a named pipe.
1319 All four variants can have the immed flag set. Then the PT and/or WUT
1321 commands are issued with the IMMED bit set and the RRTI command is used
1322 to poll for completion. The delay between the polls is as suggested by
1323 the RRTI command (or if no suggestion is made, 500 milliseconds). Ei‐
1324 ther iflag=immed, oflag=immed or both can be given but are only effec‐
1325 tive if the corresponding IFILE or OFILE sends a PT or WUT command.
1326 Typically there is no need to give the list_id=LID option. If this op‐
1328 tion is not given then 257 is chosen. If that is busy then 258 is
1329 tried. That continues until a usable LID is found or 10 LIDs have been
1330 tried. In the latter case ddpt exits with status of 55 (operation in
1331 progress). If the user gives list_id=LID option and LID is busy then
1332 ddpt exits with exit status 55.
1333 If the block size of the input and output are different (i.e. IBS is
1335 not equal to OBS) then one must be a multiple of the other. So an input
1336 block size of 512 bytes and an output block size of 4096 bytes (or vice
1337 versa) is acceptable.
1338 The four ODX variants are distinguished as follows: if OFILE is a
1340 pass-through device, if=/dev/null (or equivalent) and rtype=zero then
1341 the zero output blocks variant is selected. If both IFILE and OFILE are
1342 pass-through devices and there is some indication of an ODX request
1343 (e.g. the --odx option), then the full copy variant is selected. The
1344 read to tokens and the write from token variants are indicated by the
1345 absence of either a of=OFILE or a if=IFILE option, respectively, plus
1346 the presence of a rtf=RTF option.
1347 The helper utility ddptctl contains options to issue a single PT, RRTI,
1349 WUT or COPY OPERATION ABORT command. It can also issue a series of
1350 polling RRTI commands. It can decode information in ROD Tokens (which
1351 is not as informative as it should be) and print the number of blocks
1352 and block size of a disk, plus protection information if available. See
1353 ddptctl.
1354 There is a web page discussing ddpt, XCOPY and ODX at
1356 https://sg.danny.cz/sg/ddpt_xcopy_odx.html
1357
1359 Bypassing writes of blocks full of zeros can save a lot of IO. However
1360 with regular files, bypassed writes at the end of the copy can lead to
1361 an OFILE which is shorter than it would have been without sparse
1362 writes. This can lead to integrity checking programs like md5sum and
1363 sha1sum generating different values.
1364 This utility has two ways of handling this file length problem: writing
1366 the last block (even if it is full of zeros) or using the ftruncate
1367 system call. A third approach is to ignore the problem (i.e. leaving
1368 OFILE shorter). The ftruncate approach is used when "oflag=strunc"
1369 while the last block is written when "oflag=sparse". To ignore the file
1370 length issue use "oflag=sparse,sparse". Note that if OFILE's length is
1371 already correct or longer than required, no action is taken.
1372 The support for sparse writing of regular files may depend on the OS,
1374 the file system and the settings of OFILE. POSIX makes few guarantees
1375 when the ftruncate system call is used to extend a file's length, as
1376 may occur when "oflag=strunc". Further, primitive file systems like
1377 VFAT may not accept sparse writes or simulate the effect by writing
1378 blocks of zeros. The latter approach will defeat any sparse writing
1379 performance gain.
1380
1382 This is a new storage feature often associated with Solid State Disks
1383 (SSDs) or disk arrays with "thin provisioning". In the ATA command set
1384 (ACS-2) the relevant command is DATA SET MANAGEMENT with the TRIM bit
1385 set. In the SCSI command set (SBC-3) it is either the UNMAP or WRITE
1386 SAME command. Note there is no TRIM command however the term is fre‐
1387 quently used in the technical press.
1388 Trim is a way of telling a storage device that blocks are no longer
1390 needed. Keeping the pool of unwritten blocks large is important for
1391 the write performance of SSDs and the thrifty use of real storage in
1392 thin provisioned arrays. Currently file systems in recent OSes may is‐
1393 sue trims associated with file deletes. The trim option in ddpt may be
1394 useful when a partition or a whole SSD is to be "deleted". Note that
1395 ddpt is bypassing file systems in that it only offers trim on
1396 pass-through (pt) devices.
1397 This utility issues SCSI commands to pt devices and for "trim" cur‐
1399 rently issues a SCSI WRITE SAME(16) command with the UNMAP bit set. If
1400 the pt device is a SSD with a ATA interface then recent versions of
1401 Linux will translate the SCSI WRITE SAME to the ATA DATA SET MANAGEMENT
1402 command with the TRIM bit set. The maximum size of each "trim" command
1403 sent is the size of the copy buffer (i.e. IBS * BPT bytes). And that
1404 maximum can be reduced with the OBPC argument of the "bpt=" option.
1405 The trim can be used various ways. One way is a copy where the copy
1407 buffer (or some part of it) is checked for zeros as is done by the
1408 sparse oflag. When a zero segment is found, a trim "command" is sent to
1409 the OFILE. For example:
1410 ddpt if=dsk.img bs=512 of=/dev/sdc oflag=pt,trim
1412 The copy buffer is 64 KiB (since BPT and OBPC default to 128 when
1414 "bs=512") and it is checked for all zeros. If it is all zeros then a
1415 trim command is sent to the corresponding location of /dev/sdc which is
1416 accessed via the pt interface. If it is not all zeros then a SCSI WRITE
1417 command is sent. Another way is to trim all or part of a disk. To trim
1418 a whole disk (i.e. deleting all its data):
1419 ddpt if=/dev/zero bs=512 of=/dev/sdc oflag=pt,trim
1421 A third way is to "self-trim" which is to only trim those parts of a
1423 disk that contain segments full of zeros:
1424 ddpt if=/dev/sdc skip=0x2300 bs=512 iflag=pt,self,trim
1426 count=0x1234f0
1427 The "self" oflag automatically sets up the output side of the copy to
1429 send trim commands (if required) back the the same device (i.e.
1430 /dev/sdc). If this example was self-trimming a partition then the par‐
1431 tition would start at LBA 0x2300 and be 0x1234f0 blocks long.
1432 Some random product examples: the Intel X25-M G2 SSDs have trim with
1434 recent firmware and they do deterministic read zero after trim. The
1435 Seagate Pulsar SSD has an ATA interface which supports the determinis‐
1436 tic reads of zero after the DATA SET MANAGEMENT command with the TRIM
1437 option.
1438
1440 The following information is Linux specific at this time. NVMe devices
1441 in Linux have names like /dev/nvme0, /dev/nvme0n1 and /dev/nvme0n1p3.
1442 The first device name is a character device and some "Admin" commands
1443 can be sent to it (e.g. Identify) but no media access commands (which
1444 the NVMe specification calls the "NVM" Command set). The number given
1445 is a controller identifier. Storage in NVMe is associated with name‐
1446 spaces which are numbered within a controller, starting at 1 (e.g.
1447 /dev/nvme0n1 is controller 0, namespace 1). These device nodes are
1448 block devices and can be given as IFILE and/or OFILE. The third type of
1449 NVMe device node selects a partition (within a namespace, within a con‐
1450 troller). Partition numbers also start with 1.
1451 By default ddpt will treat the second and third form (of NVMe device
1453 nodes) as standard Linux block devices. So ddpt will act in the same as
1454 the dd utility would. In a similar fashion to accessing SCSI block de‐
1455 vices (e.g. /dev/sdc3) get access NVMe block devices the "pt" flag is
1456 required, either with iflag=FLAGS and/or oflag=FLAGS. There is a SCSI
1457 to NVMe Translation Layer (SNTL) in the sg3_utils library which under‐
1458 pins this utility.
1459
1461 dd defaults "if=" and "of=" to stdin and stdout respectively. This fol‐
1462 lows Unix filter conventions. However since dd and ddpt are often used
1463 to read binary data for timing purposes, having to supply
1464 "of=/dev/null" can be easily forgotten. Without it dd will typically
1465 spew binary data on the console. So ddpt has changed its defaults: the
1466 "if=IFILE" is now mandatory for direct copies and to read from stdin
1467 "if=-" can be used; "of=OFILE" remains optional but its default changes
1468 to "/dev/null" (or "NUL" in Windows). To send output to stdout ddpt ac‐
1469 cepts "of=-".
1470 dd truncates OFILE unless "conv=notrunc" is given. When dd truncates,
1472 it truncates to zero length unless SEEK is greater than zero. ddpt does
1473 not truncate OFILE by default. If OFILE exists it will be overwritten.
1474 The overwrite starts at block zero unless SEEK or "oflag=append" is
1475 given. If OFILE is a regular file then "oflag=trunc" (or "conv=trunc")
1476 will truncate OFILE prior to the copy.
1477 Numeric arguments to ddpt can be given in hexadecimal, either with a
1479 leading "0x" or "0X" or with a trailing "h". Note that dd accepts
1480 "0x123" but interprets it as "0 * 123" (i.e. zero). ddpt will also in‐
1481 terpret "x" as multiplies unless the left operand is zero (e.g.
1482 "0x123"). So both dd and ddpt will interpret "skip=2x123" as
1483 "skip=246".
1484 Terabyte size disks make it impractical to copy all the data into a
1486 single buffer of 512 bytes length before writing it out. Therefore both
1487 dd and ddpt read a relatively small amount of data into a copy (or
1488 transfer) buffer then write it out to the destination, repeating this
1489 process until the COUNT is exhausted.
1490 A major difference in ddpt is the addition of BPT (Blocks Per Transfer)
1492 to control the size of the copy buffer. With dd, IBS is the size of the
1493 copy buffer and the unit of SKIP and COUNT. With ddpt, IBS * BPT is the
1494 size of the copy buffer and IBS is the unit of SKIP and COUNT. This al‐
1495 lows ddpt to have its IBS set to the logical block size of IFILE with‐
1496 out unduly restricting the size of the copy buffer. And setting IBS
1497 (and OBS for OFILE) accurately is required when the pass-through inter‐
1498 face is used since with the SCSI READ and WRITE commands the logical
1499 block size is implicit.
1500 The way dd handles its copy buffer (outlined in SUSv4 description of
1502 dd) is relatively complex, especially when IBS and OBS are different
1503 sizes. The restriction that ddpt places on IBS and OBS ( i.e. (((IBS *
1504 BPT) % OBS) == 0) ) means that a single copy buffer can be used since
1505 its size is a multiple of both IBS and OBS. Being able to precisely de‐
1506 fine the copy buffer size in ddpt makes sparse writing, write sparing
1507 and trim operations simpler to define and the user to control.
1508 ddpt does not support dd's "cbs=" option (conversion block size). If
1510 the "cbs=" option is given to ddpt then it is ignored.
1511 ddpt adds two types of disk to disk, offloaded copies: XCOPY(LID1)
1513 first introduced in SPC-2 (standardized in 2001), and ODX which is a
1514 subset of XCOPY(LID4) first introduced in SPC-4 draft (revision 34,
1515 2012).
1516
1518 This section is about protection information which is typically an ex‐
1519 tra 8 bytes associated with each logical block. Those 8 byte are di‐
1520 vided into 3 fields: logical block guard (16 bit (2 byte) CRC), logical
1521 block application tag (2 bytes) and the logical block reference tag (4
1522 bytes). The acronym DIF is sometimes used for protection information.
1523 The feature to read and/or write protection information by using the
1525 protect=RDP[,WRP] option is currently experimental. It should be used
1526 with care and may not "play well" with some other features such as
1527 write sparing and sparse writing. It should be used to copy user data
1528 plus the associated protection information to or from a regular file.
1529 It could also be used for a device to device copy assuming the "pt" in‐
1530 terface is used for both. Also only modern SCSI disks support protec‐
1531 tion information.
1532 When RDP or WRP is greater than 0 then a copy with associated protec‐
1534 tion information is active. In this state IBS and OBS must be the same
1535 and equal to the logical block size of the device(s) formatted with
1536 protection information. If a SCSI disk with 512 byte logical block size
1537 has protection information then the actual number of bytes transferred
1538 for each logical block is typically 520 bytes. For such a disk BS=512
1539 is required even when additional protection information is being trans‐
1540 ferred.
1541 When protection type 2 is used, the "normal" READ, WRITE and VERIFY
1543 SCSI commands are disallowed. In this context "normal" means the 6, 10,
1544 12, and 16 byte variants. Only READ(32) and WRITE(32) can be used. The
1545 32 byte variants can be selected in this utility by using the operand
1546 'cdbsz=32'.
1547
1549 By default numeric arguments to options are assumed to be decimal. Al‐
1550 most all numeric arguments to options (e.g. COUNT in the count=COUNT
1551 option) may include one of these multiplicative suffixes: c C *1; w W
1552 *2; b B *512; k K KiB *1,024; KB *1,000; m M MiB *1,048,576; MB
1553 *1,000,000 . This pattern continues for "G", "T" and "P". The latter
1554 two suffixes can only be used for 64 bit values. Some numeric arguments
1555 are limited to 32 bit values (e.g. BSin the bs=BS option). Also a suf‐
1556 fix of the form "x<n>" multiplies the leading number by <n>; however
1557 the combinations "0x" and "0X" are treated differently, see the next
1558 paragraph. These multiplicative suffixes are compatible with GNU's dd
1559 command (since 2002) which claims compliance with the SI and with IEC
1560 60027-2 standards.
1561 Alternatively numerical values can be given in hexadecimal indicated by
1563 either a leading "0x" or "0X", or by a trailing "h" or "H". When hex
1564 numbers are given, suffix multipliers cannot be used.
1565 If a numeric argument is required to fit in 32 bits and is too large
1567 then an error is reported. Usually negative numbers are not permitted
1568 but "count=-1" is a special case and means "all available"; "ver‐
1569 bose=-1" is another special case.
1570
1572 Copying data behind an Operating System's back can cause problems. In
1573 the case of Linux, users should look at this link:
1574 https://linux-mm.org/Drop_Caches
1575 This command sequence may be useful:
1576 sync; echo 3 > /proc/sys/vm/drop_caches
1577 A partial write is a write to the OFILE of less than OBS bytes. This
1579 typically occurs at the end of a copy. dd can do partial writes. ddpt
1580 does partial writes to regular files and fifos (including stdout). How‐
1581 ever ddpt ignores partial writes when OFILE is a block device or a pt
1582 device. When ddpt ignores a partial write, it sends a warning to the
1583 console (stderr).
1584 At the end of the copy two lines are reported to the console:
1586 <in_full>+<in_partial> records in
1587 <out_full>+<out_partial> records out
1588 The "records in" line is the number of full input blocks (each of IBS
1590 bytes) that have been read plus the number of partial blocks ( usually
1591 less than IBS bytes) that have been read. Following the lead of dd when
1592 'iflag=coe' is active a block that cannot be read (and has zeros sub‐
1593 stituted for its output) is regarded as a partial read. The "records
1594 out" line is the number of full output blocks (each of OBS bytes) that
1595 have been written plus the number of partial blocks (usually less than
1596 OBS bytes) that have been written.
1597 Block devices (e.g. /dev/sda and /dev/hda) can be given for IFILE. If
1599 neither 'iflag=direct' nor 'iflag=pt' is given then normal block IO in‐
1600 volving buffering and caching is performed. If 'iflag=direct' is given
1601 then the buffering and caching is bypassed (this is applicable to both
1602 SCSI devices and ATA disks). When 'iflag=pt' is given SCSI commands are
1603 sent to the device which bypasses most of the actions performed by the
1604 block layer. The same applies for block devices given for OFILE.
1605 All informative, warning and error reports are sent to stderr so that
1607 dd's output file can be stdout and remain unpolluted. If no options are
1608 given, then no copying (nor reading) takes place and a brief message is
1609 sent to stderr inviting the user to invoke ddpt again but with '--help'
1610 option to get the usage message.
1611 Disk partition information can often be found with fdisk(8) [the "-ul"
1613 argument is useful in this respect]. Also parted(8) can be used like
1614 this: 'parted /dev/sda unit s print' .
1615 For pt devices this utility issues SCSI READ and WRITE (SBC) commands
1617 which are appropriate for disks and reading from CD/DVD/BD drives.
1618 Those commands are not formatted correctly for tape drives so ddpt can‐
1619 not be used on tape drives via a pt device. If the largest block ad‐
1620 dress of the requested transfer exceeds a 32 bit block number (i.e
1621 0xffffffff) then a warning is issued and the pt device is accessed via
1622 SCSI READ(16) and WRITE(16) commands.
1623 The attributes of a block device (e.g. partitions) are ignored when the
1625 pt flag is used. Hence the whole device is read (rather than just the
1626 second partition) by this invocation:
1627 ddpt if=/dev/sdb2 iflag=pt of=t bs=512
1629 Assuming /dev/sdb and /dev/sg2 refer to the same device, then after the
1631 following two invocations, the contents of the files "t", "tt" and
1632 "ttt" should be same:
1633 ddpt if=/dev/sdb of=tt bs=512
1635 ddpt if=/dev/sg2 of=ttt bs=512
1637 The SCSI READ(32) and WRITE(32) commands are restricted to media that
1639 is formatted with protection type 2. This is a T10 restriction.
1640
1642 The signal handling has been borrowed from GNU's dd: SIGINT, SIGQUIT
1643 and SIGPIPE report the number of remaining blocks to be transferred and
1644 the records in + out counts; then they have their default action. SI‐
1645 GUSR1 (or SIGINFO) causes the same information to be output and the
1646 copy continues. All output caused by signals is sent to stderr.
1647 Like GNU's dd, ddpt respects the signal disposition of "ignored"
1649 (SIG_IGN) set by the shell, script or other program that invokes ddpt.
1650 So in that case it will ignore such signals. Further dd ignores SIGUSR1
1651 if the environment variable POSIXLY_CORRECT is set because POSIX de‐
1652 fines dd will only act on SIGINFO (and Linux has no such signal); ddpt
1653 ignores the POSIXLY_CORRECT environment variable. As recommended by
1654 Susv3, ddpt does not expect the signal (blocking) mask to be blocking
1655 SIGUSR1 (SIGINFO), SIGINT or SIGPIPE on entry.
1656 Unix system calls that do IO can be interrupted by signal processing,
1658 typically returning an EINTR error number. The dd utility (and many
1659 other Unix utilities) restart the IO operation that was interrupted.
1660 While this will work most of the time for disk IO it is problematic for
1661 tape drives because the implicit position pointer on the tape may have
1662 moved. So the default (i.e. "intio=0") in this utility is to mask
1663 those signals during IO operations and only check them prior to start‐
1664 ing an IO operation. Most low level IO (e.g. using SCSI command to
1665 write to a disk) will timeout if there is a low level error. However
1666 NFS (the Network File System) will potentially wait for a long time
1667 (e.g. expecting a network problem will soon be fixed) and in this case
1668 using "intio=1" may be best.
1669
1671 The usual way to check the two disks (or part of the disks) are the
1672 same is to move through the segments to be compared, reading from both
1673 and comparing the returned buffers, stopping if there is an in equal‐
1674 ity.
1675 This utility takes a different approach that relies on the OFILE being
1677 a pass through device. That pass-through device needs to support the
1678 SCSI VERIFY command with the BYTCHK field set to 1. Optionally, for the
1679 --prefetch option to improve performance that pass-through device needs
1680 to support the SCSI PRE-FETCH command with its IMMED bit set.
1681 When the --verify option is given, instead of reading both IFILE and
1683 OFILE, only the IFILE is read. Then the result of that read is sent to
1684 the OFILE device as the data-out buffer of a VERIFY(BYTCHK=1) command.
1685 So the comparison is actually done on the OFILE device rather than the
1686 host computer's main memory.
1687 If the --prefetch option is also given, then before the IFILE read, a
1689 PRE-FETCH(OFILE, IMMED) is sent. The IMMED bit will make it return more
1690 or less immediately. The effect of the PRE-FETCH should be to bring the
1691 contents of the data to be used for the OFILE side of the comparison,
1692 into the OFILE device's cache. And that should make the later VER‐
1693 IFY(BYTCHK=1) command faster.
1694
1696 There is support for copies to and from tape drives in Linux. Only the
1697 st driver device names can be used (e.g. /dev/st0 and /dev/nst2). Hence
1698 use of Linux pass-through device names (e.g. /dev/sg2) for tape drives
1699 is not supported. On Debian-based distributions, it is suggested that
1700 the mt-st package is installed as it provides a more fully-featured
1701 version of the "mt" tape control program.
1702 Tape drives can operate in fixed- or variable-length block modes. In
1704 variable-block mode, each write to the tape writes a single block of
1705 that size. In fixed-block mode, each write to the tape must be a multi‐
1706 ple of the previously-selected block size.
1707 The block size/mode can be set with the mt command prior to invoking
1709 ddpt. For example:
1710 # mt -f /dev/nst0 setblk 0
1711 sets variable-block mode, and
1712 # mt -f /dev/nst0 setblk 32768
1713 sets fixed-block mode with block size 32768 bytes.
1714 Note that some tape drives support only fixed-block mode, and possibly
1716 even only one block size. (For example, QIC-150 tapes use a fixed block
1717 size of 512 bytes.) There may also be restrictions on the block size,
1718 e.g. it may have to be even.
1719 When using ddpt to write to tape, if the final read from the input is
1721 less than OBS, it is padded to OBS bytes before writing to tape to en‐
1722 sure that all blocks of the tape file are the same length. Having a
1723 shorter final block would fail if the drive is in fixed-block mode, and
1724 could create interchange problems. It is common to expect all blocks in
1725 a file on tape to be the same length. However, to tell ddpt to not pad
1726 the final block, use 'oflag=nopad'.
1727 The st tape driver normally writes a filemark when the file (e.g.
1729 /dev/nst0) is closed. To not have the filemark written, use
1730 'oflag=nofm'. One use case for that might be if using ddpt several
1731 times in succession to append more data to the same file on tape. In
1732 that case it is probably desirable to write the filemark at the end of
1733 the sequence. So either omit 'oflag=nofm' on the last ddpt invocation,
1734 or manually write a filemark using mt after ddpt exits:
1735 # mt -f /dev/nst0 weof 1
1736 For reading from an unknown tape where the block size(s) is not known,
1738 read in variable-block mode specifying a large IBS. The st driver re‐
1739 turns a smaller amount of data if the size of the block read is
1740 smaller. Thus a command like:
1741 # ddpt if=/dev/nst0 of=output.bin bs=262144
1742 should read the file from tape regardless of the block size used (as‐
1743 suming no blocks are larger than 256KB). ddpt's verbose option will
1744 display what the actual block size(s) is.
1745
1747 If the command line invocation of an xcopy does not explicitly (and un‐
1748 ambiguously) indicate whether the XCOPY SCSI command should be sent to
1749 IFILE (i.e. the source) or OFILE (i.e. the destination) then a check
1750 is made for the presence of the XCOPY_TO_SRC and XCOPY_TO_DST environ‐
1751 ment variables. If either one exists (but not both) then it indicates
1752 where the SCSI XCOPY command will be sent. By default the XCOPY command
1753 is sent to OFILE.
1754 The ODX write from tokens variant is very complex to implement if the
1756 amount of data held in each ROD is not known. The value should be found
1757 in the "number of bytes represented" field in the ROD Token but that is
1758 not well supported yet by vendors. So for such cases, that number can
1759 be appended as a big endian 8 byte integer following each ROD Token in
1760 the RTF file. The conv=rtf_len will cause that length to be appended.
1761 Specifying that option on each read to tokens and write from tokens in‐
1762 vocation can be a nuisance. Setting the environment variable
1763 ODX_RTF_LEN will cause this utility to act as if the conv=rtf_len op‐
1764 tion has been given.
1765 Sometimes the default block size of 512 can be a nuisance. This can be
1767 overridden by the value associated with the DDPT_DEF_BS environment
1768 variable. If the environment variable is not found, the value cannot be
1769 decoded or is zero or less, then the default block size remains at 512
1770 bytes.
1771
1773 To aid scripts that call ddpt, the exit status is set to indicate suc‐
1774 cess (0) or failure (1 or more). Note that some of the lower values
1775 correspond to the SCSI sense key values. The exit status values are:
1776 0 success. Also conveys boolean true for actions that result in
1778 true or false (e.g. sgl equality tests)
1779 1 syntax error. Either illegal command line options, options with
1781 bad arguments or a combination of options that is not permitted.
1782 2 the device reports that it is not ready for the operation re‐
1784 quested. The device may be in the process of becoming ready
1785 (e.g. spinning up but not at speed) so the utility may work af‐
1786 ter a wait.
1787 3 the device reports a medium or hardware error (or a blank
1789 check). For example an attempt to read a corrupted block on a
1790 disk will yield this value.
1791 5 the device reports an "illegal request" with an additional sense
1793 code other than "invalid operation code". This is often a sup‐
1794 ported command with a field set requesting an unsupported capa‐
1795 bility.
1796 6 the device reports a "unit attention" condition. This usually
1798 indicates that something unrelated to the requested command has
1799 occurred (e.g. a device reset) potentially before the current
1800 SCSI command was sent. The requested command has not been exe‐
1801 cuted by the device. Note that unit attention conditions are
1802 usually only reported once by a device.
1803 7 the device reports a "data protect" sense key. This implies some
1805 mechanism has blocked writes (or possibly all access to the me‐
1806 dia).
1807 9 the device reports an illegal request with an additional sense
1809 code of "invalid operation code" which means that it doesn't
1810 support the requested command.
1811 10 the device reports a "copy aborted". This implies another com‐
1813 mand or device problem has stopped and copy operation. The EX‐
1814 TENDED COPY family of commands (including WRITE USING TOKEN) may
1815 return this sense key.
1816 11 the device reports an aborted command. In some cases aborted
1818 commands can be retried immediately (e.g. if the transport
1819 aborted the command due to congestion).
1820 14 the DEVICE reports a miscompare sense key. VERIFY and COMPARE
1822 AND WRITE commands may report this.
1823 15 the utility is unable to open, close or use the given IFILE,
1825 OFILE or other file. The given file name could be incorrect or
1826 there may be permission problems. Adding the -v option may give
1827 more information.
1828 20 the device reports it has a check condition but "no sense". It
1830 is unlikely that this value will occur as an exit status.
1831 21 the device reports a "recovered error". The requested command
1833 was successful. Most likely a utility will report a recovered
1834 error to stderr and continue, probably leaving the utility with
1835 an exit status of 0 .
1836 24 the device reports a SCSI status of "reservation conflict". This
1838 means access to the device with the current command has been
1839 blocked because another machine (HBA or SCSI "initiator") holds
1840 a reservation on this device. On modern SCSI systems this is re‐
1841 lated to the use of the PERSISTENT RESERVATION family of com‐
1842 mands.
1843 25 the DEVICE reports a SCSI status of "condition met". Currently
1845 only the PRE-FETCH command (see SBC-4) yields this status.
1846 26 the DEVICE reports a SCSI status of "busy". SAM-5 defines this
1848 status as the logical unit is temporarily unable to process a
1849 command. It is recommended to re-issue the command.
1850 27 the DEVICE reports a SCSI status of "task set full".
1852 28 the DEVICE reports a SCSI status of "ACA active". ACA is "auto
1854 contingent allegiance" and is seldom used.
1855 29 the DEVICE reports a SCSI status of "task aborted". SAM-5 says:
1857 "This status shall be returned if a command is aborted by a com‐
1858 mand or task management function on another I_T nexus and the
1859 Control mode page TAS bit is set to one".
1860 31 error involving two or more command line options. Either they
1862 contradict or select an unsupported mode.
1863 32 the is a logic error in the utility. It corresponds to code com‐
1865 ments like "shouldn't/can't get here". Perhaps the author should
1866 be contacted.
1867 33 the command sent to device has timed out. This occurs in Linux
1869 only; in other ports a command timeout will appear as a trans‐
1870 port (or OS) error.
1871 36 no error has occurred. For actions that result in a boolean,
1873 this exit status indicates false.
1874 40 the command sent to a device has received an "aborted command"
1876 sense key with an additional sense code of 0x10. This value is
1877 related to problems with protection information (PI or DIF). For
1878 example this error may occur when reading a block on a drive
1879 that has never been written (or is unmapped) if that drive was
1880 formatted with type 1, 2 or 3 protection.
1881 48 this is an internal message indicating a NVMe status field (SF)
1883 is other than zero after a command has been executed (i.e. some‐
1884 thing went wrong). Work in this area is currently experimental.
1885 49 low level driver reports a response's residual count (i.e. num‐
1887 ber of bytes actually received by HBA is 'requested_bytes -
1888 residual_count') that is too high. So no useful processing can
1889 be done with that response.
1890 50 + <os_error_number>
1892 OS system calls that fail often return a small integer number to
1893 help indicate what the error is. For example in Unix the inabil‐
1894 ity of a system call to allocate memory returns (in 'errno')
1895 ENOMEM which often is associated with the integer 12. So 62
1896 (i.e. '50 + 12') may be returned by a utility in this case.
1897 90 the flock flag has been given on a device and some other process
1899 holds the advisory exclusive lock.
1900 97 the response to a SCSI command failed sanity checks.
1902 98 the device reports it has a check condition but the error
1904 doesn't fit into any of the above categories.
1905 99 any errors that can't be categorized into values 1 to 98 may
1907 yield this value. This includes transport and operating system
1908 errors after the command has been sent to the device.
1909 100 a command received a 'parameter list length error'.
1911 101 a command received 'illegal field in parameter list'. This may
1913 occur with an odx copy if some combination of parameters is il‐
1914 legal or not supported (e.g. iflag=immed).
1915 105 a command received 'operation in progress'. This may occur with
1917 an odx copy when the given LID is already being used by another
1918 process (e.g. also using odx) on the same machine. Choose an‐
1919 other LID.
1920 110 a command received 'invalid token operation, cause not re‐
1922 portable'. This may occur with an odx operation when the given
1923 ROD Token is invalid. One reason for that may be the inactivity
1924 timeout has been reached and the copy manager has cancelled the
1925 ROD Token.
1926 110 + <asc_23h_ascq_code>
1928 these status values provide more information than exit status
1929 110. See SPC-5 ASC and ASCQ assignments (currently in Annex
1930 F.2), specifically the entries for asc=23h . For example exit
1931 status 112 corresponds to asc=23h, ascq=2h which implies the odx
1932 copy manager does not support copies between LUs in different
1933 targets. That is optional; an odx copy manager is required to
1934 support copies between LUs (that are block devices) in the same
1935 target.
1936 126 the utility was found but could not be executed. That might oc‐
1938 cur if the executable does not have execute permissions.
1939 127 This is the exit status for utility not found. That might occur
1941 when a script calls a utility in this package but the PATH envi‐
1942 ronment variable has not been properly set up, so the script
1943 cannot find the executable.
1944 128 + <signum>
1946 If a signal kills a utility then the exit status is 128 plus the
1947 signal number. For example if a segmentation fault occurs then a
1948 utility is typically killed by SIGSEGV which according to 'man 7
1949 signal' has an associated signal number of 11; so the exit sta‐
1950 tus will be 139 .
1951 255 the utility tried to yield an exit status of 255 or larger. That
1953 should not happen; given here for completeness.
1954
1956 The examples in this page use Linux device names. For suitable device
1957 names in other supported Operating Systems see this web page:
1958 https://sg.danny.cz/sg/device_name.html . The sg3_utils(8) man page in
1959 the sg3_utils package also covers device naming.
1960 ddpt usage looks quite similar to dd:
1962 ddpt if=/dev/sg0 of=t bs=512 count=1MB
1964 This will copy 1 million 512 byte blocks from the device associated
1966 with /dev/sg0 (which should have 512 byte blocks) to a file called t.
1967 Assuming /dev/sda and /dev/sg0 are the same device then the above is
1968 equivalent to:
1969 dd if=/dev/sda iflag=direct of=t bs=512 count=1000000
1971 although dd's speed may improve if bs was larger and count was suitably
1973 reduced. The use of the 'iflag=direct' option bypasses the buffering
1974 and caching that is usually done on a block device.
1975 The dd command's bs argument can be thought of as roughly equivalent to
1977 ddpt's bs*bpt . dd almost assumes buffering on a block device and will
1978 work as long as bs is a multiple of the actual logical block size.
1979 Since ddpt can work at a lower level in some cases the bs argument must
1980 be a disk's actual logical block size. Thus the bpt argument was intro‐
1981 duced to make the copy more efficient. So these two invocations are
1982 roughly equivalent:
1983 dd if=/dev/sda of=t bs=8k count=64
1985 ddpt if=/dev/sda of=t bs=512 bpt=16 count=1k
1986 In both cases the total number of bytes moved is bs*count . And that
1988 will be done by reading 8k (8192 bytes) into a buffer then writing out
1989 that buffer to the file t. The read write sequence continues until the
1990 count is complete or an error occurs.
1991 The 'of2=' option can save time when the input would otherwise need to
1993 be read twice. For example, to copy data and take a md5sum of it with‐
1994 out needing to re-read the data:
1995 mkfifo fif
1997 md5sum fif &
1998 ddpt if=/dev/sg3 iflag=coe of=sg3.img oflag=sparse of2=fif bs=512
1999 This will image /dev/sg3 (e.g. an unmounted disk) and place the con‐
2001 tents in the (sparse) file sg3.img . Without re-reading the data it
2002 will also perform a md5sum calculation on the image.
2003 Now we use sparse writing logic to get some idea of how many blocks on
2005 a disk are full of zeros. After a SCSI FORMAT UNIT command or an ATA
2006 SECURITY ERASE command a disk may be all zeros.
2007 ddpt if=/dev/sdc bs=512 oflag=sparse
2009 Since no "of=" option is given, output goes to /dev/null so nothing is
2011 actually written so the "records out" will be zero. However there will
2012 be a count of "records in" and "bypassed records out". If /dev/sdc is
2013 full of zeros then "records in" and "bypassed records out" will be the
2014 same. Since the "bpt=" option is not given it defaults to "bpt=128,128"
2015 so the copy buffer will be 64 KiB and the sparse check for zeros will
2016 be done with 64 KiB (128 block) granularity.
2017 For examples of the trim and self,trim options see the section above on
2019 TRIM, UNMAP AND WRITE SAME.
2020 Following is an example run on a Windows OS using the '--wscan' option
2022 which shows the available device names (e.g. PD1) and the associated
2023 volume name(s):
2024 ddpt -w
2026 PD0 [C] FUJITSU MHY2160BH 0000
2027 PD1 [DF] WD 2500BEV External 1.05 WD-WXE90
2028 CDROM0 [E] MATSHITA DVD/CDRW UJDA775 CB03
2029 So, for example, volumes D: and F: reside on PhysicalDisk1 (abbreviated
2031 to "PD1") which is manufactured by WD (Western Digital).
2032 Further examples can be found on this web page:
2034 https://sg.danny.cz/sg/ddpt.html . There is a text file containing ex‐
2035 amples called ddpt_examples.txt in the "doc" directory of this pack‐
2036 age's distribution tarball. The ddpt_examples.txt file contains some
2037 examples of using job files.
2038
2040 Written by Doug Gilbert
2041
2043 Report bugs to <dgilbert at interlog dot com>.
2044
2046 Copyright © 2008-2021 Douglas Gilbert
2047 This software is distributed under the GPL version 2. There is NO war‐
2048 ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
2049 POSE.
2050
2052 This utility has companion/helper utilities ddptctl(8), ddpt_sgl(8)
2053 There is a web page discussing ddpt at https://sg.danny.cz/sg/ddpt.html
2054 The lmbench package contains lmdd which is also interesting. For moving
2056 data to and from tapes see dt which is found at http://www.scsi‐
2057 faq.org/RMiller_Tools/index.html
2058 To change mode parameters that effect a SCSI device's caching and error
2060 recovery see sdparm(sdparm)
2061 To verify the data on the media is readable see: sg_verify(sg3_utils)
2063 To scan and repair disk partitions see TestDisk (testdisk).
2065 Additional references: dd(1), open(2), flock(2), sg_xcopy,sg_copy_re‐
2067 sults, sg_dd(sg3_utils)
2068ddpt-0.97 April 2021 DDPT(8)