在安装文件系统时用到了dd命令，对它不是很熟悉，就查了下它的用法，和大家share下
一.dd命令
1.我们先在终端输入命令： man dd，看以下官方的解释 ：
NAME
dd - convert and copy a file
SYNOPSIS
dd [OPERAND]...
dd OPTION
DESCRIPTION
Copy a file, converting and formatting according to the operands.
bs=BYTES
read and write BYTES bytes at a time (also see ibs=,obs=)
cbs=BYTES
convert BYTES bytes at a time
conv=CONVS
convert the file as per the comma separated symbol list
count=BLOCKS
copy only BLOCKS input blocks
ibs=BYTES
read 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=BLOCKS
skip BLOCKS obs-sized blocks at start of output
skip=BLOCKS
skip BLOCKS ibs-sized blocks at start of input
status=noxfer
suppress transfer statistics
BLOCKS and BYTES may be followed by the following multiplicative suf‐
fixes: 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.
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
nocreat
do not create the output file
excl fail if the output file already exists
notrunc
do not truncate the output file
ucase change lower case to upper case
swab swap every pair of input bytes
noerror
continue after read errors
sync pad every input block with NULs to ibs-size; when used with
block or unblock, pad with spaces rather than NULs
fdatasync
physically write output file data before finishing
fsync likewise, but also write metadata
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