root@kali:~# dc3dd --help
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usage:
------
dc3dd [OPTION 1] [OPTION 2] ... [OPTION N]
*or*
dc3dd [HELP OPTION]
where each OPTION is selected from the basic or advanced
options listed below, or HELP OPTION is selected from the
help options listed below.
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basic options:
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if=DEVICE or FILE Read input from a device or a file (see note #1
below for how to read from standard input). This
option can only be used once and cannot be
combined with ifs=, pat=, or tpat=.
ifs=BASE.FMT Read input from a set of files with base name
BASE and sequential file name extensions
conforming to the format specifier FMT (see note
#4 below for how to specify FMT). This option
can only be used once and cannot be combined with
if=, pat=, or tpat=.
of=FILE or DEVICE Write output to a file or device (see note #2
below for how to write to standard output). This
option can be used more than once (see note #3
below for how to generate multiple outputs).
hof=FILE or DEVICE Write output to a file or device, hash the
output bytes, and verify by comparing the output
hash(es) to the input hash(es). This option can
be used more than once (see note #3 below for
how to generate multiple outputs).
ofs=BASE.FMT Write output to a set of files with base name BASE
and sequential file name extensions generated from
the format specifier FMT (see note #4 below for
how to specify FMT). This option can be used more
than once (see note #3 below for how to generate
multiple outputs). Specify the maximum size of
each file in the set using ofsz=.
hofs=BASE.FMT Write output to a set of files with base name BASE
and sequential file name extensions generated from
the format specifier FMT (see note #4 below for
how to specify FMT). Hash the output files and
verify by comparing the output hash(es) to the
input hash(es). This option can be used more than
once (see note #3 below for how to generate
multiple outputs). Specify the maximum size of
each file in the set using ofsz=.
ofsz=BYTES Set the maximum size of each file in the sets of
files specified using ofs= or hofs= to
BYTES (see note #5 below). A default value for
this option may be set at compile time using
-DDEFAULT_OUTPUT_FILE_SIZE followed by the desired
value in BYTES.
hash=ALGORITHM Compute an ALGORITHM hash of the input and also
of any outputs specified using hof=, hofs=,
or fhod=, where ALGORITHM is one of md5, sha1,
sha256, or sha512. This option may be used once
for each supported ALGORITHM. Alternatively,
hashing can be activated at compile time using one
or more of -DDEFAULT_HASH_MD5,-DDEFAULT_HASH_SHA1,
-DDEFAULT_HASH_SHA256, and -DDEFAULT_HASH_SHA512.
log=FILE Log I/O statistcs, diagnostics, and total hashes
of input and output to FILE. If hlog= is not
specified, piecewise hashes of multiple file
input and output are also logged to FILE. This
option can be used more than once to generate
multiple logs.
hlog=FILE Log total hashes and piecewise hashes to FILE.
This option can be used more than once to generate
multiple logs.
mlog=FILE Create hash log that is easier for machine to read
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advanced options:
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fhod=DEVICE The same as hof=DEVICE, with additional
hashing of the entire output DEVICE. This option
can be used more than once (see note #3 below
for how to generate multiple outputs).
rec=off By default, zeros are written to the output(s) in
place of bad sectors when the input is a device.
Use this option to cause the program to instead
exit when a bad sector is encountered.
wipe=DEVICE Wipe DEVICE by writing zeros (default) or a
pattern specified by pat= or tpat=.
hwipe=DEVICE Wipe DEVICE by writing zeros (default) or a
pattern specified by pat= or tpat=. Verify
DEVICE after writing it by hashing it and
comparing the hash(es) to the input hash(es).
pat=HEX Use pattern as input, writing HEX to every byte
of the output. This option can only be used once
and cannot be combined with if=, ifs=, or
tpat=.
tpat=TEXT Use text pattern as input, writing the string TEXT
repeatedly to the output. This option can only be
used once and cannot be combined with if=, ifs=,
or pat=.
cnt=SECTORS Read only SECTORS input sectors. Must be used
with pat= or tpat= if not using the pattern with
wipe= or hwipe= to wipe a device.
iskip=SECTORS Skip SECTORS sectors at start of the input device
or file.
oskip=SECTORS Skip SECTORS sectors at start of the output
file. Specifying oskip= automatically
sets app=on.
app=on Do not overwrite an output file specified with
of= if it already exists, appending output instead.
ssz=BYTES Unconditionally use BYTES (see note #5 below) bytes
for sector size. If ssz= is not specified,
sector size is determined by probing the device;
if the probe fails or the target is not a device,
a sector size of 512 bytes is assumed.
bufsz=BYTES Set the size of the internal byte buffers to BYTES
(see note #5 below). This effectively sets the
maximum number of bytes that may be read at a time
from the input. BYTES must be a multiple of sector
size. Use this option to fine-tune performance.
verb=on Activate verbose reporting, where sectors in/out
are reported for each file in sets of files
specified using ifs=, ofs=, or hofs=.
Alternatively, verbose reporting may be activated
at compile time using -DDEFAULT_VERBOSE_REPORTING.
nwspc=on Activate compact reporting, where the use
of white space to divide log output into
logical sections is suppressed. Alternatively,
compact reporting may be activated at compile
time using -DDEFAULT_COMPACT_REPORTING.
b10=on Activate base 10 bytes reporting, where the
progress display reports 1000 bytes instead
of 1024 bytes as 1 KB. Alternatively, base 10
bytes reporting may be activated at compile
time using -DDEFAULT_BASE_TEN_BYTES_REPORTING.
corruptoutput=on For verification testing and demonstration
purposes, corrupt the output file(s) with extra
bytes so a hash mismatch is guaranteed.
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help options:
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--help display this help and exit
--version output version information and exit
--flags display compile-time flags and exit
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notes:
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1. To read from stdin, do not specify if=, ifs=, pat=, or tpat=.
2. To write to stdout, do not specify of=, hof=, ofs=, hofs=, fhod=,
wipe=, or hwipe=.
3. To write to multiple outputs specify more than one of of=, hof=, ofs=,
hofs=, or fhod=, in any combination.
4. FMT is a pattern for a sequence of file extensions that can be numerical
starting at zero, numerical starting at one, or alphabetical. Specify FMT
by using a series of zeros, ones, or a's, respectively. The number of
characters used indicates the desired length of the extensions.
For example, a FMT specifier of 0000 indicates four character
numerical extensions starting with 0000.
5. 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), GB (1000*1000*1000), G (1024*1024*1024), and
so on for T, P, E, Z, and Y.
6. Consider using cnt=, iskip= and oskip= to work around
unreadable sectors if error recovery fails.
7. Sending an interrupt (e.g., CTRL+C) to dc3dd will cause
the program to report the work completed at the time
the interrupt is received and then exit.
dc3dd completed at 2026-06-17 10:37:00 -0400
dc3dd Usage Example
root@kali:~# dc3dd if=/var/log/messages of=/tmp/dc3dd hash=sha512
dc3dd 7.2.646 started at 2018-12-01 13:37:20 -0500
compiled options:
command line: dc3dd if=/var/log/messages of=/tmp/dc3dd hash=sha512
sector size: 512 bytes (assumed)
42015925 bytes ( 40 M ) copied ( 100% ), 0 s, 185 M/s
input results for file `/var/log/messages':
82062 sectors + 181 bytes in
2dd19a4fd6bdebddf2ce754f4b09f7914b7cb7433efc5b8678ff437d9e13857995815c2b63ae4722a6d4c143347458497fb6b1b4a1ef4e4fd3c5d9cd08111f16 (sha512)
output results for file `/tmp/dc3dd':
82062 sectors + 181 bytes out
dc3dd completed at 2018-12-01 13:37:21 -0500