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diff --git a/doc/sgm_dd.8 b/doc/sgm_dd.8 new file mode 100644 index 00000000..58782d72 --- /dev/null +++ b/doc/sgm_dd.8 @@ -0,0 +1,284 @@ +.TH SGM_DD "8" "February 2019" "sg3_utils\-1.45" SG3_UTILS +.SH NAME +sgm_dd \- copy data to and from files and devices, especially SCSI +devices +.SH SYNOPSIS +.B sgm_dd +[\fIbs=BS\fR] [\fIcount=COUNT\fR] [\fIibs=BS\fR] [\fIif=IFILE\fR] +[\fIiflag=FLAGS\fR] [\fIobs=BS\fR] [\fIof=OFILE\fR] [\fIoflag=FLAGS\fR] +[\fIseek=SEEK\fR] [\fIskip=SKIP\fR] [\fI\-\-help\fR] [\fI\-\-version\fR] +.PP +[\fIbpt=BPT\fR] [\fIcdbsz=\fR6|10|12|16] [\fIdio=\fR0|1] [\fIsync=\fR0|1] +[\fItime=\fR0|1] [\fIverbose=VERB\fR] [\fI\-\-dry\-run\fR] +[\fI\-\-verbose\fR] +.SH DESCRIPTION +.\" Add any additional description here +.PP +Copy data to and from any files. Specialized for "files" that are +Linux SCSI generic (sg) devices and raw devices. Uses memory mapped +transfers on sg devices. Similar syntax and semantics to +.B dd(1) +but does not perform any conversions. +.PP +Will only perform memory mapped transfers when \fIIFILE\fR or \fIOFILE\fR +are SCSI generic (sg) devices. +.PP +If both \fIIFILE\fR and \fIOFILE\fR are sg devices then memory mapped +transfers are performed on \fIIFILE\fR. If no other flags are specified +then indirect IO is performed on \fIOFILE\fR. If 'oflag=dio' is given then +direct IO is attempted on \fIOFILE\fR. If direct IO is not available, then +this utility falls back to indirect IO and reports this at the end of the +copy. +.PP +The first group in the synopsis above are "standard" Unix +.B dd(1) +operands. The second group are extra options added by this utility. +Both groups are defined below. +.SH OPTIONS +.TP +\fBbpt\fR=\fIBPT\fR +each IO transaction will be made using \fIBPT\fR blocks (or less if +near the end of the copy). Default is 128 for block sizes less that 2048 +bytes, otherwise the default is 32. So for bs=512 the reads and writes +will each convey 64 KiB of data by default (less if near the end of the +transfer or memory restrictions). When cd/dvd drives are accessed, the +block size is typically 2048 bytes and bpt defaults to 32 which again +implies 64 KiB transfers. +.TP +\fBbs\fR=\fIBS\fR +where \fIBS\fR +.B must +be the block size of the physical device. Note that this differs from +.B dd(1) +which permits \fIBS\fR to be an integral multiple. Default is 512 which +is usually correct for disks but incorrect for cdroms (which normally +have 2048 byte blocks). For this utility the maximum size of each individual +IO operation is \fIBS\fR * \fIBPT\fR bytes. +.TP +\fBcdbsz\fR=6 | 10 | 12 | 16 +size of SCSI READ and/or WRITE commands issued on sg device names. +Default is 10 byte SCSI command blocks (unless calculations indicate +that a 4 byte block number may be exceeded, in which case it defaults +to 16 byte SCSI commands). +.TP +\fBcount\fR=\fICOUNT\fR +copy \fICOUNT\fR blocks from \fIIFILE\fR to \fIOFILE\fR. Default is the +minimum (of \fIIFILE\fR and \fIOFILE\fR) number of blocks that sg devices +report from SCSI READ CAPACITY commands or that block devices (or their +partitions) report. Normal files are not probed for their size. If +\fIskip=SKIP\fR or \fIseek=SEEK\fR are given and the count is derived (i.e. +not explicitly given) then the derived count is scaled back so that the +copy will not overrun the device. If the file name is a block device +partition and \fICOUNT\fR is not given then the size of the partition rather +than the size of the whole device is used. If \fICOUNT\fR is not given and +cannot be derived then an error message is issued and no copy takes place. +.TP +\fBdio\fR=0 | 1 +permits direct IO to be selected on the write\-side (i.e. on \fIOFILE\fR). +Only allowed when the read\-side (i.e. \fIIFILE\fR) is a sg device. When +1 there may be a "zero copy" copy (i.e. mmap\-ed transfer on the read into +the user space and direct IO from there on the write, potentially two DMAs +and no data copying from the CPU). Default is 0. +The same action as 'dio=1' is also available with 'oflag=dio'. +.TP +\fBibs\fR=\fIBS\fR +if given must be the same as \fIBS\fR given to 'bs=' option. +.TP +\fBif\fR=\fIIFILE\fR +read from \fIIFILE\fR instead of stdin. If \fIIFILE\fR is '\-' then stdin +is read. Starts reading at the beginning of \fIIFILE\fR unless \fISKIP\fR +is given. +.TP +\fBiflag\fR=\fIFLAGS\fR +where \fIFLAGS\fR is a comma separated list of one or more flags outlined +below. These flags are associated with \fIIFILE\fR and are ignored when +\fIIFILE\fR is stdin. +.TP +\fBobs\fR=\fIBS\fR +if given must be the same as \fIBS\fR given to 'bs=' option. +.TP +\fBof\fR=\fIOFILE\fR +write to \fIOFILE\fR instead of stdout. If \fIOFILE\fR is '\-' then writes +to stdout. If \fIOFILE\fR is /dev/null then no actual writes are performed. +If \fIOFILE\fR is '.' (period) then it is treated the same way as +/dev/null (this is a shorthand notation). If \fIOFILE\fR exists then it +is _not_ truncated; it is overwritten from the start of \fIOFILE\fR +unless 'oflag=append' or \fISEEK\fR is given. +.TP +\fBoflag\fR=\fIFLAGS\fR +where \fIFLAGS\fR is a comma separated list of one or more flags outlined +below. These flags are associated with \fIOFILE\fR and are ignored when +\fIOFILE\fR is /dev/null, '.' (period), or stdout. +.TP +\fBseek\fR=\fISEEK\fR +start writing \fISEEK\fR bs\-sized blocks from the start of \fIOFILE\fR. +Default is block 0 (i.e. start of file). +.TP +\fBskip\fR=\fISKIP\fR +start reading \fISKIP\fR bs\-sized blocks from the start of \fIIFILE\fR. +Default is block 0 (i.e. start of file). +.TP +\fBsync\fR=0 | 1 +when 1, does SYNCHRONIZE CACHE command on \fIOFILE\fR at the end of the +transfer. Only active when \fIOFILE\fR is a sg device file name. +.TP +\fBtime\fR=0 | 1 +when 1, times transfer and does throughput calculation, outputting the +results (to stderr) at completion. When 0 (default) doesn't perform timing. +.TP +\fBverbose\fR=\fIVERB\fR +as \fIVERB\fR increases so does the amount of debug output sent to stderr. +Default value is zero which yields the minimum amount of debug output. +A value of 1 reports extra information that is not repetitive. A value +2 reports cdbs and responses for SCSI commands that are not repetitive +(i.e. other that READ and WRITE). Error processing is not considered +repetitive. Values of 3 and 4 yield output for all SCSI commands (and +Unix read() and write() calls) so there can be a lot of output. +.TP +\fB\-d\fR, \fB\-\-dry\-run\fR +does all the command line parsing and preparation but bypasses the actual +copy or read. That preparation may include opening \fIIFILE\fR or +\fIOFILE\fR to determine their lengths. This option may be useful for +testing the syntax of complex command line invocations in advance of +executing them. +.TP +\fB\-h\fR, \fB\-\-help\fR +outputs usage message and exits. +.TP +\fB\-v\fR, \fB\-\-verbose\fR +when used once, this is equivalent to \fIverbose=1\fR. When used +twice (e.g. "\-vv") this is equivalent to \fIverbose=2\fR, etc. +.TP +\fB\-V\fR, \fB\-\-version\fR +outputs version number information and exits. +.SH FLAGS +Here is a list of flags and their meanings: +.TP +append +causes the O_APPEND flag to be added to the open of \fIOFILE\fR. For normal +files this will lead to data appended to the end of any existing data. +Cannot be used together with the \fIseek=SEEK\fR option as they conflict. +The default action of this utility is to overwrite any existing data +from the beginning of the file or, if \fISEEK\fR is given, starting at +block \fISEEK\fR. Note that attempting to 'append' to a device file (e.g. +a disk) will usually be ignored or may cause an error to be reported. +.TP +dio +is only active with oflag (i.e. 'oflag=dio'). Its action is described in +the 'dio=1' option description above. +.TP +direct +causes the O_DIRECT flag to be added to the open of \fIIFILE\fR and/or +\fIOFILE\fR. This flag requires some memory alignment on IO. Hence user +memory buffers are aligned to the page size. Has no effect on sg, normal +or raw files. +.TP +dpo +set the DPO bit (disable page out) in SCSI READ and WRITE commands. Not +supported for 6 byte cdb variants of READ and WRITE. Indicates that +data is unlikely to be required to stay in device (e.g. disk) cache. +May speed media copy and/or cause a media copy to have less impact +on other device users. +.TP +dsync +causes the O_SYNC flag to be added to the open of \fIIFILE\fR and/or +\fIOFILE\fR. The "d" is prepended to lower confusion with the 'sync=0|1' +option which has another action (i.e. a synchronisation to media at the +end of the transfer). +.TP +excl +causes the O_EXCL flag to be added to the open of \fIIFILE\fR and/or +\fIOFILE\fR. +.TP +fua +causes the FUA (force unit access) bit to be set in SCSI READ and/or WRITE +commands. This only has effect with sg devices. The 6 byte variants +of the SCSI READ and WRITE commands do not support the FUA bit. +Only active for sg device file names. +.TP +null +has no affect, just a placeholder. +.SH RETIRED OPTIONS +Here are some retired options that are still present: +.TP +fua=0 | 1 | 2 | 3 +force unit access bit. When 3, fua is set on both \fIIFILE\fR and +\fIOFILE\fR; when 2, fua is set on \fIIFILE\fR; when 1, fua is set on +\fIOFILE\fR; when 0 (default), fua is cleared on both. See the 'fua' flag. +.SH NOTES +A raw device must be bound to a block device prior to using sgm_dd. +See +.B raw(8) +for more information about binding raw devices. To be safe, the sg device +mapping to SCSI block devices should be checked with the lsscsi utility +before use. +.PP +Raw device partition information can often be found with +.B fdisk(8) +[the "\-ul" argument is useful in this respect]. +.PP +Various numeric arguments (e.g. \fISKIP\fR) may include multiplicative +suffixes or be given in hexadecimal. See the "NUMERIC ARGUMENTS" section +in the sg3_utils(8) man page. +.PP +The count, skip and seek parameters can take 64 bit values (i.e. very +big numbers). Other values are limited to what can fit in a signed +32 bit number. +.PP +Data usually gets to the user space in a 2 stage process: first the +SCSI adapter DMAs into kernel buffers and then the sg driver copies +this data into user memory (write operations reverse this sequence). +With memory mapped transfers a kernel buffer reserved by sg is memory +mapped (see the +.B mmap(2) +system call) into the user space. When this is done +the second (redundant) copy from kernel buffers to user space is +not needed. Hence the transfer is faster and requires less "grunt" +from the CPU. +.PP +All informative, warning and error output is sent to stderr so that +dd's output file can be stdout and remain unpolluted. If no options +are given, then the usage message is output and nothing else happens. +.PP +For sg devices this utility issues SCSI READ and WRITE (SBC) commands which +are appropriate for disks and reading from CD/DVD/BD drives. Those commands +are not formatted correctly for tape devices so sgm_dd should not be used +on tape devices. +.PP +This utility stops the copy if any error is encountered. For more +advanced "copy on error" logic see the +.B sg_dd +utility (and its 'coe' flag). +.SH EXAMPLES +See the examples given in the man page for +.B sg_dd(8). +.SH SIGNALS +The signal handling has been borrowed from dd: SIGINT, SIGQUIT and +SIGPIPE output the number of remaining blocks to be transferred and +the records in + out counts; then they have their default action. +SIGUSR1 causes the same information to be output yet the copy continues. +All output caused by signals is sent to stderr. +.SH EXIT STATUS +The exit status of sgm_dd is 0 when it is successful. Otherwise see +the sg3_utils(8) man page. Since this utility works at a higher level +than individual commands, and there are 'coe' and 'retries' flags, +individual SCSI command failures do not necessary cause the process +to exit. +.SH AUTHORS +Written by Douglas Gilbert and Peter Allworth. +.SH "REPORTING BUGS" +Report bugs to <dgilbert at interlog dot com>. +.SH COPYRIGHT +Copyright \(co 2000\-2019 Douglas Gilbert +.br +This software is distributed under the GPL version 2. There is NO +warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. +.SH "SEE ALSO" +The simplest variant of this utility is called +.B sg_dd. +A POSIX threads version of this utility called +.B sgp_dd +is in the sg3_utils package. The lmbench package contains +.B lmdd +which is also interesting. +.B dd(1), ddpt(ddpt), raw(8) |