Input file is taken from
internal is the default.
internal is a special file that acts like Suns
/dev/zero, i.e., it provides a buffer of zeros without doing a system call to get them.
The following file names are taken to mean the standard input: -, 0, or stdin.
Output file is taken from
internal is the default.
internal is a special file that acts like
/dev/null, without doing a system call to get rid of the data.
The following file names are taken to mean the standard output: -, 1, or stdout.
The following file names are taken to mean the standard error: 2, or stderr.
|bs=n||Input and output block size n bytes (default 8192). Note that this is different from dd(1), it has a 512 byte default. Also note that the block size can be followed by k or m to indicate kilo bytes (*1024) or megabytes (*1024*1024), respectively.|
|ipat=n||If n is non zero, expect a known pattern in the file (see opat). Mismatches will be displayed as "ERROR: off=%d want=%x got=%x". The pattern is a sequence of 4 byte integers with the first 0, second 1, and so on. The default is not to check for the pattern.|
|opat=n||If n is non zero, generate a known pattern on the output stream. Used for debugging file system correctness. The default is not to generate the pattern.|
|mismatch=n||If n is non zero, stop at the first mismatched value. Used with ipat.|
|skip=n||Skip n input blocks before starting copy.|
|fsync=n||If n is non-zero, call fsync(2) on the output file before exiting or printing timing statistics.|
|sync=n||If n is non-zero, call sync(2) before exiting or printing timing statistics.|
|rand=n||This argument, by default off, turns on random behavior. The argument is not a flag, it is a size, that size is used as the upper bound for the seeks. Also note that the block size can be followed by k or m to indicate kilo bytes (*1024) or megabytes (*1024*1024),|
|flush=n||If n is non-zero and mmap(2) is available, call msync(2) to invalidate the output file. This flushes the file to disk so that you dont have unmount/mount. It is not as good as mount/unmount because it just flushes file pages - it misses the indirect blocks which are still cached. Not supported on all systems, compile time option.|
|rusage=n||If n is non-zero, print rusage statistics as well as timing statistics. Not supported on all systems, compile time option.|
|count=n||Copy only n input records.|
This is the most common usage, the intent is to measure disk performance. The disk is a spare partition mounted on /spare.
# mount /spare # lmdd if=internal of=/spare/XXX count=1000 fsync=1 7.81 MB in 3.78 seconds (2.0676 MB/sec)
: Flush cache # umount /spare # mount /spare
# lmdd if=/spare/XXX of=internal 7.81 MB in 2.83 seconds (2.7611 MB/sec)
Larry McVoy, firstname.lastname@example.org
|(c)1994 Larry McVoy||LMDD (8)||$Date$|