Name

Synopsis

Description

Options

if=name

Input file is taken from name; internal is the default. internal is a special file that acts like Sun’s /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.

of=name

Output file is taken from name; 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 don’t 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.

Examples

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)

Author

Table of Contents

• Name
• Synopsis
• Description
• Options
• Examples
• Author