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Diffstat (limited to 'sgm_dd.8')
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diff --git a/sgm_dd.8 b/sgm_dd.8 new file mode 100644 index 00000000..4d18f877 --- /dev/null +++ b/sgm_dd.8 @@ -0,0 +1,121 @@ +.TH SGM_DD "8" "January 2002" "sg3_utils-0.98" SG3_UTILS +.SH NAME +sgm_dd \- copies data to and from sg and raw devices +.SH SYNOPSIS +.B sgm_dd +[\fIOPTION\fR]... +.SH DESCRIPTION +.\" Add any additional description here +.PP +Copy data to and from Linux SCSI generic (sg) and raw devices +using memory mapped IO. Similar syntax and semantics to +.B dd(1) +but does not perform any conversions. +.TP +bpt=BLOCKS +each IO transaction will be made using this number of blocks (or less if +near the end of count). Default is 128. +.TP +bs=BYTES +this +.B must +be the block size of the physical device. Note that this differs from +.B dd(1) +which permits "bs" to be an integral multiple. Default is 512 which +is usually correct for disks but incorrect for cdroms (which normally +have 2048 byte blocks). +.TP +count=BLOCKS +copy this number of blocks. Default is minimum number that sg devices +return from READ CAPACITY (if that works) or 0 +.TP +ibs=BYTES +if given must be the same as bs +.TP +if=FILE +read from FILE instead of stdin. A file name of - is taken to be stdin +.TP +obs=BYTES +if given must be the same as bs +.TP +of=FILE +write to FILE instead of stdout. A file name of - is taken to be stdout +.TP +seek=BLOCKS +skip BLOCKS bs-sized blocks at start of output +.TP +skip=BLOCKS +skip BLOCKS bs-sized blocks at start of input +.TP +time=0 | 1 +when 1, times transfer and does throughput calculation, outputting the +results (to stderr) at completion. When 0 (default) doesn't perform timing +.TP +--version +outputs version number information and exits +.PP +Either the input file or the output file must be a sg or raw device. +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 "cat /proc/scsi/scsi" +before use. +.PP +The count is only deduced for sg devices (minimum > 0 if both input and +output are sg devices) otherwise it defaults to 0. This is for safety! +Raw device partition information can often be found with +.B fdisk(8) +[the "-ul" argument is useful in this respect]. +.PP +BYTES and BLOCKS may be followed by the following multiplicative suffixes: +c C *1; b B *512; k *1,024; K *1,000; m *1,048,576; M *1,000,000; +g *1,073,741,824; and G *1,000,000,000 +.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 IO 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. +.SH EXAMPLES +.PP +See the examples given in the man page for +.B sg_dd(8). +.SH NOTE +For sg devices this command issues READ_10 and WRITE_10 SCSI commands which +are appropriate for disks and CDROM players. Those commands are not +formatted correctly for tape devices so sgm_dd should not be used on +tape devices. +.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 AUTHORS +Written by Doug Gilbert and Peter Allworth. +.SH "REPORTING BUGS" +Report bugs to <dgilbert@interlog.com>. +.SH COPYRIGHT +Copyright \(co 2000-2002 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 command is called +.B sg_dd. +A POSIX threads version of this command called +.B sgp_dd +is in the sg3_utils package. The lmbench package contains +.B lmdd +which is also interesting. +.B raw(8), dd(1) |