linux命令行輸入：
dd --help
Usage: dd [OPERAND]...
or: 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 skip N obs-sized blocks at start of output
skip=N skip N ibs-sized blocks at start of input
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.
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 the output for NUL input 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
count_bytes treat 'count=N' as a byte count (iflag only)
skip_bytes treat 'skip=N' as a byte count (iflag only)
seek_bytes treat 'seek=N' as a byte count (oflag only)
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
GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: <http://www.gnu.org/software/coreutils/dd>
or available locally via: info '(coreutils) dd invocation'
中文翻譯如下：
用法：dd [OPERAND] ......
或者：dd OPTION
根據操作數複製文件，轉換和格式化。
bs = BYTES一次讀取和寫入BYTES字節（默認值：512）;
覆蓋ibs和obs
cbs = BYTES一次轉換BYTES字節
conv = CONVS按照逗號分隔的符號列表轉換文件
count = N僅複製N個輸入塊
ibs = BYTES一次讀取BYTES字節（默認值：512）
if = FILE從FILE而不是stdin讀取
iflag = FLAGS按逗號分隔的符號列表讀取
obs = BYTES一次寫BYTES字節（默認值：512）
of = FILE寫入FILE而不是stdout
oflag = FLAGS根據逗號分隔的符號列表寫入
seek = N在輸出開始時跳過N個阻塞大小的塊
skip = N在輸入開始時跳過N ibs大小的塊
status = LEVEL要打印到stderr的信息的級別;
'none'除了錯誤消息外都會抑制所有內容，
'noxfer'抑制最終轉移統計，
'progress'顯示定期傳輸統計信息
N和BYTES之後可以跟隨以下乘法後綴：
c = 1，w = 2，b = 512，kB = 1000，K = 1024，MB = 1000 * 1000，M = 1024 * 1024，xM = M，
對於T，P，E，Z，Y，GB = 1000 * 1000 * 1000，G = 1024 * 1024 * 1024等。
每個CONV符號可以是：
ascii從EBCDIC到ASCII
從ASCII到EBCDIC的ebcdic
從ASCII到交替EBCDIC的ibm
阻止填充換行符終止的記錄，其空格爲cbs-size
unblock用換行符替換cbs-size記錄中的尾隨空格
lcase將大寫更改爲小寫
ucase將小寫更改爲大寫
稀疏嘗試尋找而不是寫入NUL輸入塊的輸出
swab交換每對輸入字節
每個輸入塊同步填充NUL到ibs大小; 使用時
使用block或unblock，填充空格而不是NUL
如果輸出文件已存在，則excl失敗
nocreat不創建輸出文件
notrunc不截斷輸出文件
閱讀錯誤後，noerror繼續
fdatasync在完成之前物理寫入輸出文件數據
fsync同樣，但也寫入元數據
每個FLAG符號可能是：
追加附加模式（僅對輸出有意義;建議使用conv = notrunc）
直接使用直接I / O數據
目錄失敗，除非目錄
dsync使用同步I / O進行數據
同樣地同步，但也用於元數據
fullblock累積整個輸入塊（僅限iflag）
非阻塞使用非阻塞I / O.
noatime不更新訪問時間
nocache請求刪除緩存。另見oflag = sync
noctty不從文件中分配控制終端
nofollow不遵循符號鏈接
count_bytes將'count = N'視爲字節數（僅限iflag）
skip_bytes將'skip = N'視爲字節數（僅限iflag）
seek_bytes將'seek = N'視爲字節數（僅限oflag）
將USR1信號發送到正在運行的'dd'進程就可以了
將I / O統計信息打印到標準錯誤，然後重新開始複製。
選項包括：
--help顯示此幫助並退出
--version輸出版本信息並退出
GNU coreutils在線幫助：<http://www.gnu.org/software/coreutils/>
完整文檔：<http://www.gnu.org/software/coreutils/dd>
或通過以下方式在本地獲取：info'（coreutils）dd invocation'
範例如下：
1）把A文件(bootsect)內容拷貝到B文件(boot.img)
dd if=bootsect of=boot.img
2）從A文件(bootsect)拷貝指定字節BYTES的數據到B文件(boot.img)
dd ibs=BYTES if=bootsect of=boot.img
3）把A文件(system)指定字節後的內容拷貝到到B文件(boot.img)指定位置處，字節=ibs*seek參數
dd ibs=160 skip=1 seek=1 if=system of=boot.img