Standard
dd options |
Default |
Brief
description |
bs=<block_size> |
512 |
Number of bytes in each block |
count=<count_of_blocks> | blocks in input file |
Number of blocks to copy |
if=<input_file> | stdin |
file (or device) to read from |
of=<output_file> | stdout |
file (or device) to write to.
Doesn't bother writing anything if <output_file> is /dev/null or
. (period). |
Standard
dd options |
Default |
Brief
description |
ibs=<block_size> | same as bs |
number of bytes in each block of
<input_file> |
iflag=<flags> |
[new in sg3_utils 1.18] similar
to option found in recent GNU dd versions, see below |
|
obs=<block_size> | same as bs |
number of bytes in each block of <output_file> |
oflag=<flags> |
[new in sg3_utils 1.18] similar
to option found in recent GNU dd versions,see below |
|
seek=<n_blocks_of> | 0 |
block number (origin 0) in
<output_file> to commence writing |
seek=<n_blocks_of> | 0 |
block number (origin 0) in <input_file> to commence reading |
--help |
print usage message then exit |
|
--version |
print version number and its
date then exit |
Multiplier |
Meaning |
x<n> |
*<n> |
c |
*1 |
w |
*2 |
b |
*512 |
k K KiB |
*1024 |
KB |
*1000 |
m M MiB |
*1048576 |
MB |
*1000000 |
g G GiB |
2**30 |
GB |
10**9 |
t T TiB |
2**40 |
TB |
10**12 |
flag |
sg
device |
block
device |
regular
file |
comments |
append |
ignored |
applied on <ofile> |
applied on <ofile> |
use O_APPEND open flag.
Conflicts with 'seek=<n>'. |
coe |
applied |
applied if using SG_IO ioctl | ignored |
continue on error; best effort
recovery then continue |
direct |
applied |
applied |
applied |
use O_DIRECT open flag, no
effect with sg devices |
dpo |
applied |
applied if using SG_IO ioctl | ignored | "disable page out" set for READ and/or WRITE SCSI commands |
dsync |
applied |
applied |
applied |
use O_SYNC open flag, no effect
with sg devices |
excl |
applied |
applied |
applied |
Use O_EXCL open flag |
fua |
applied |
applied if using SG_IO ioctl |
ignored |
"force unit access" set for READ
and/or WRITE SCSI commands |
sgio |
ignored |
use SG_IO ioctl |
ignored |
access block device via SG_IO
ioctl (only supported in lk 2.6 series) |
extra
options in sg_dd |
default |
Brief
description |
append=0|1 |
0 |
append to output file (rather
than overwrite). Better to use 'iflag=append' and/or 'oflag=append'. |
blk_sgio=0|1 |
0 |
when set access devices via SCSI
commands (SG_IO ioctl). May use 'iflag=sgio' and/or 'oflag=sgio'
instead. |
bpt |
128 or 32 |
blocks_per_transfer (granularity
of each IO). Default is 128 when bs < 2048 (bytes) else the default
is 32. For block devices (bpt * bs) is constrained by /sys/block/<device>/queue/max_sectors_kb
. |
cdbsz=6|10|12|16 |
10 or 16 |
cdb size of SCSI READ and/or
WRITE commands. Only applicable to sg devices or when the SG_IO ioctl
is being used (e.g. when blk_sgio=1) |
coe=0|1 |
0 |
when set, continue_on_error for sg devices and block devices using the SG_IO ioctl. May use 'iflag=coe' and/or 'oflag=coe' instead. |
dio=0|1 |
0 |
direct IO (only via sg device
nodes) |
fua=0|1|2|3 |
0 |
force_unit_access, 1->if, 2->of, 3->if+of . Better to use 'iflag=fua' and/or 'oflag=fua'. |
odir=0|1 |
0 |
O_DIRECT flag on open() when set. Better to use 'iflag=direct' and/or 'oflag=direct'. |
sync=0|1 |
0 |
when set, sends SYNCHRONIZE
CACHE SCSI command to <ofile> if it is a sg device or accessed
via the SG_IO ioctl. |
time=0|1 |
0 |
when set print elapsed time and
throughput after copy |
verbose=<n> |
0 |
larger <n> is the greater
the debug output |
File
type |
open
[when input] |
open
[when output] |
IO
method |
Notes |
normal |
O_RDONLY |
O_WRONLY | O_CREAT |
Unix read() write() |
N.B. A normal output file is
overwritten (not truncated). |
stdin or stdout |
[do nothing] |
[do nothing] |
Unix read() write() |
hence open() flags have no
effect (e.g. 'oflag=direct') |
/dev/null or . (period) |
O_RDONLY | [do nothing] |
Unix read() if input |
if output file then nothing is
written |
block device |
O_RDONLY | O_WRONLY | O_CREAT |
Unix read() write() | |
block device [sgio flag given] |
O_RDWR or O_RDONLY | O_RDWR | SCSI commands | Opens input O_RDONLY if O_RDWR fails. The 'blk_sgio=1' option equates to both 'iflag=sgio' and 'oflag=sgio'. Partition ignored. |
sg device |
O_RDWR or O_RDONLY |
O_RDWR |
SCSI commands |
Opens input O_RDONLY if O_RDWR fails |
raw device |
O_RDONLY | O_WRONLY |
Unix read() write() |
O_DIRECT open flag in lk 2.6
series is a replacement for raw devices |
scsi tape device |
x |
x |
no IO |
error reported |
Return to main page.
Last updated: 18th November 2005