Linux中的dd命令
阿新 • • 發佈：2017-05-20
linux dd
一、dd命令用指定大小的塊拷貝一個文件，並在拷貝的同時進行指定的轉換。
使用方法：dd [OPERAND]
參數註釋：
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=N copy only N input blocks
ibs=BYTES read BYTES bytes at a time (default: 512)
if=FILE read from FILE instead of stdin(默認為標準輸入)
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(默認為標準輸出)
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=WHICH WHICH info to suppress outputting to stderr;
‘noxfer‘ suppresses transfer stats, ‘none‘ suppresses allCONVS的可選參數
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
sparse try to seek rather than write the output for NUL input blocks
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 metadataFLAGS的可選參數
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 noctty do not assign controlling terminal from file nofollow do not follow symlinks count_bytes treat ‘count=N‘ as a byte count (iflag only)
註意：指定數字的地方若以下列字符結尾，則乘以相應的數字：
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
二、使用實例
1、將本地的/dev/hdb整盤備份到/dev/hdd
dd if=/dev/hdb of=/dev/hdd
2、將/dev/hdb全盤數據備份到指定路徑的image文件
dd if=/dev/hdb of=/root/image
3、備份/dev/hdb全盤數據，並利用gzip工具進行壓縮，保存到指定路徑
dd if=/dev/hdb | gzip > /root/image.gz
4、把一個文件拆分為3個文件
#文件大小為2.3k [[email protected] ~]$ ll db1_db_links.sql -rw-r--r-- 1 oracle oinstall 2344 Nov 21 10:39 db1_db_links.sql #把這個文件拆成每個文件1k，bs=1k，count=1，使用skip參數指定在輸入文件中跳過多少個bs支讀取 [[email protected] ~]$ dd if=db1_db_links.sql of=dd01.sql bs=1k count=1 1+0 records in 1+0 records out 1024 bytes (1.0 kB) copied, 4.5536e-05 s, 22.5 MB/s [[email protected] ~]$ dd if=db1_db_links.sql of=dd02.sql bs=1k count=1 skip=1 1+0 records in 1+0 records out 1024 bytes (1.0 kB) copied, 0.000146387 s, 7.0 MB/s [[email protected] ~]$ dd if=db1_db_links.sql of=dd03.sql bs=1k count=1 skip=2 0+1 records in 0+1 records out 296 bytes (296 B) copied, 0.000204216 s, 1.4 MB/s #拆分出的文件 [[email protected] ~]$ ll dd*sql -rw-r--r-- 1 oracle oinstall 1024 May 20 14:58 dd01.sql -rw-r--r-- 1 oracle oinstall 1024 May 20 14:58 dd02.sql -rw-r--r-- 1 oracle oinstall 296 May 20 14:58 dd03.sql
5、把拆分出的文件合並為1個
#合並操作，此時用到seek參數，用於指定在輸入文件中跳過的bs數 [[email protected] ~]$ dd of=1.sql if=dd01.sql 2+0 records in 2+0 records out 1024 bytes (1.0 kB) copied, 0.000176 s, 5.8 MB/s [[email protected] ~]$ dd of=1.sql if=dd02.sql bs=1k seek=1 1+0 records in 1+0 records out 1024 bytes (1.0 kB) copied, 0.000124038 s, 8.3 MB/s [[email protected] ~]$ dd of=1.sql if=dd03.sql bs=1k seek=2 0+1 records in 0+1 records out 296 bytes (296 B) copied, 0.00203881 s, 145 kB/s #與拆分前的文件進行校驗 [[email protected] ~]$ diff 1.sql db1_db_links.sql [[email protected] ~]$
6、在輸出文件中指定的位置插入數據，而不截斷輸出文件
需要使用conv=notrunc參數 [[email protected] ~]$ dd if=2.sql of=1.sql bs=1k seek=1 count=2 conv=notrunc
參考：http://blog.csdn.net/xizaihui/article/details/53307578
http://blog.csdn.net/jijiagang/article/details/42192049
本文出自 “DBA Fighting!” 博客，請務必保留此出處http://hbxztc.blog.51cto.com/1587495/1927774
Linux中的dd命令