linux 操作系统下dd 命令介绍和使用案例
1. dd 命令简介
dd 命令是一个功能强大的 Linux 工具,用于转换和复制文件。它的主要用途包括:
- 创建引导盘
- 备份和恢复磁盘分区
- 创建磁盘镜像
- 清除磁盘数据
- 测试读写性能
dd 命令的语法与大多数 Linux 命令有所不同,使用 option=value 的形式指定选项。
2. dd 命令常用选项
- if=FILE: 指定输入文件
- of=FILE: 指定输出文件
- bs=BYTES: 设置读写的块大小
- count=BLOCKS: 仅复制指定数量的块
- skip=BLOCKS: 跳过输入文件开头的指定数量的块
- seek=BLOCKS: 跳过输出文件开头的指定数量的块
- conv=CONVS: 指定文件转换选项
命令选项：
root@meng:~# dd
^Z
1\]+ Stopped dd
root@meng:\~# which dd
/usr/bin/dd
root@meng:\~# dd -help
dd: invalid option -- 'h'
Try 'dd --help' for more information.
root@meng:\~# 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.
Binary prefixes can be used, too: KiB=K, MiB=M, and so on.
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
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: \