dd指令以指定大小的區塊拷貝一個文件，並在拷貝的同時進行指定的轉換。以下這篇文章主要為大家介紹了關於Linux中dd指令使用的相關資料，對大家具有一定的參考學習價值，需要的朋友們下面來一起看看吧。
本文主要介紹了Linux中dd指令使用的相關內容，分享出來供大家參考學習，以下來看看詳細的介紹：
一、Linux dd指令以指定大小的區塊拷貝一個文件，並在拷貝的同時進行指定的轉換。
使用方法：dd [OPERAND]
#參數註解：
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(默认为标准输入)
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(默认为标准输出)
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 metadata
FLAGS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)
注意： 指定數字的地方若以下列字元結尾，則乘以對應的數字：
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、將本機的/dev/hdb整盤備份到/dev/hdd
dd if=/dev/hdb of=/dev/hdd
2、將/dev/hdb全碟資料備份到指定路徑的image檔
dd if=/dev/hdb of=/root/image
3、備份/dev/hdb全碟數據，並利用gzip工具進行壓縮，儲存到指定路徑
dd if=/dev/hdb | gzip > /root/image.gz
#4、把一個檔案拆分為3個檔案
#文件大小为2.3k [Oracle@rhel6 ~]$ ll db1_db_links.sql -rw-r--r-- 1 oracle oinstall 2344 Nov 21 10:39 db1_db_links.sql #把这个文件拆成每个文件1k，bs=1k，count=1，使用skip参数指定在输入文件中跳过多少个bs支读取 [oracle@rhel6 ~]$ 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 [oracle@rhel6 ~]$ 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 [oracle@rhel6 ~]$ 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 [oracle@rhel6 ~]$ 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、把拆分出的檔案合併為1個
#合并操作，此时用到seek参数，用于指定在输入文件中跳过的bs数 [oracle@rhel6 ~]$ 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 [oracle@rhel6 ~]$ 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 [oracle@rhel6 ~]$ 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 #与拆分前的文件进行校验 [oracle@rhel6 ~]$ diff 1.sql db1_db_links.sql [oracle@rhel6 ~]$
6.在輸出檔中指定的位置插入資料，而不截斷輸出檔
#需要使用conv=notrunc參數
[oracle@rhel6 ~]$ dd if=2.sql of=1.sql bs=1k seek=1 count=2 conv=notrunc
總結
#以上是Linux中關於dd指令的使用實例教程的詳細內容。更多資訊請關注PHP中文網其他相關文章！
