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NAME | SYNOPSIS | DESCRIPTION | AUTHOR | REPORTING BUGS | COPYRIGHT | SEE ALSO | COLOPHON |
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DD(1) User Commands DD(1)
dd - convert and copy a file
dd [OPERAND]...
dd OPTION
Copy a file, converting and formatting according to the operands.
bs=BYTES
read and write up to BYTES bytes at a time (default: 512);
overrides ibs and obs
cbs=BYTES
convert BYTES bytes at a time
conv=CONVS
convert the file as per the comma separated symbol list
count=N
copy only N input blocks
ibs=BYTES
read up to BYTES bytes at a time (default: 512)
if=FILE
read from FILE instead of stdin
iflag=FLAGS
read as per the comma separated symbol list
obs=BYTES
write BYTES bytes at a time (default: 512)
of=FILE
write to FILE instead of stdout
oflag=FLAGS
write as per the comma separated symbol list
seek=N (or oseek=N) skip N obs-sized output blocks
skip=N (or iseek=N) skip N ibs-sized input blocks
status=LEVEL
The LEVEL of information to print to stderr; 'none'
suppresses everything but error messages, 'noxfer'
suppresses the final transfer statistics, 'progress' shows
periodic transfer statistics
N and BYTES may be followed by the following multiplicative
suffixes: c=1, w=2, b=512, kB=1000, K=1024, MB=1000*1000,
M=1024*1024, xM=M, GB=1000*1000*1000, G=1024*1024*1024, and so on
for T, P, E, Z, Y, R, Q. Binary prefixes can be used, too: KiB=K,
MiB=M, and so on. If N ends in 'B', it counts bytes not blocks.
Each CONV symbol may be:
ascii from EBCDIC to ASCII
ebcdic from ASCII to EBCDIC
ibm from ASCII to alternate EBCDIC
block pad newline-terminated records with spaces to cbs-size
unblock
replace trailing spaces in cbs-size records with newline
lcase change upper case to lower case
ucase change lower case to upper case
sparse try to seek rather than write all-NUL output blocks
swab swap every pair of input bytes
sync pad every input block with NULs to ibs-size; when used with
block or unblock, pad with spaces rather than NULs
excl fail if the output file already exists
nocreat
do not create the output file
notrunc
do not truncate the output file
noerror
continue after read errors
fdatasync
physically write output file data before finishing
fsync likewise, but also write metadata
Each FLAG symbol may be:
append append mode (makes sense only for output; conv=notrunc
suggested)
direct use direct I/O for data
directory
fail unless a directory
dsync use synchronized I/O for data
sync likewise, but also for metadata
fullblock
accumulate full blocks of input (iflag only)
nonblock
use non-blocking I/O
noatime
do not update access time
nocache
Request to drop cache. See also oflag=sync
noctty do not assign controlling terminal from file
nofollow
do not follow symlinks
Sending a USR1 signal to a running 'dd' process makes it print I/O
statistics to standard error and then resume copying.
Options are:
--help display this help and exit
--version
output version information and exit
Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
GNU coreutils online help:
<https://www.gnu.org/software/coreutils/>
Report any translation bugs to
<https://translationproject.org/team/>
Copyright © 2025 Free Software Foundation, Inc. License GPLv3+:
GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Full documentation <https://www.gnu.org/software/coreutils/dd>
or available locally via: info '(coreutils) dd invocation'
This page is part of the coreutils (basic file, shell and text
manipulation utilities) project. Information about the project
can be found at ⟨http://www.gnu.org/software/coreutils/⟩. If you
have a bug report for this manual page, see
⟨http://www.gnu.org/software/coreutils/⟩. This page was obtained
from the tarball coreutils-9.7.tar.xz fetched from
⟨http://ftp.gnu.org/gnu/coreutils/⟩ on 2025-08-11. If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for the
page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
GNU coreutils 9.7 April 2025 DD(1)
Pages that refer to this page: pipesz(1), truncate(1), xfs(5), fdisk(8), sfdisk(8), swapon(8), xfs_copy(8), xfs_repair(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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