2021-05-12 14:32:11
Linux中的dd命令使用範例
2020-06-16 17:14:36
一、Linux dd命令用指定大小的塊拷貝一個檔案，並在拷貝的同時進行指定的轉換。
使用方法：dd [OPERAND]
引數注釋：
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(預設為標准輸入) 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(預設為標準輸出) 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的可選引數
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的可選引數
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：指定數位的地方若以下列字元結尾，則乘以相應的數位：
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、使用範例
1、將原生的/dev/hdb整盤備份到/dev/hdd
dd if=/dev/hdb of=/dev/hdd2、將/dev/hdb全盤資料備份到指定路徑的image檔案
dd if=/dev/hdb of=/root/image3、備份/dev/hdb全盤資料，並利用gzip工具進行壓縮，儲存到指定路徑
dd if=/dev/hdb | gzip > /root/image.gz4、把一個檔案拆分為3個檔案
#檔案大小為2.3k [Oracle@rhel6 ~]$ ll db1_db_links.sql -rw-r--r-- 1 oracle oinstall 2344 Nov 21 10:39 db1_db_links.sql #把這個檔案拆成每個檔案1k，bs=1k，count=1，使用skip引數指定在輸入檔案中跳過多少個bs支讀取 [oracle@rhel6 ~]$ dd if=db1_db_links.sql of=dd01.sql bs=1k count=1 1+0 records in1+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 in1+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 in0+1 records out 296 bytes (296 B) copied, 0.000204216 s, 1.4 MB/s#拆分出的檔案 [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.sql5、把拆分出的檔案合併為1個
#合併操作，此時用到seek引數，用於指定在輸入檔案中跳過的bs數 [oracle@rhel6 ~]$ dd of=1.sql if=dd01.sql 2+0 records in2+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 in1+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 in0+1 records out 296 bytes (296 B) copied, 0.00203881 s, 145 kB/s#與拆分前的檔案進行校驗 [oracle@rhel6 ~]$ diff 1.sql db1_db_links.sql [oracle@rhel6 ~]$6、在輸出檔案中指定的位置插入資料，而不截斷輸出檔案
需要使用conv=notrunc引數 [oracle@rhel6 ~]$ dd if=2.sql of=1.sql bs=1k seek=1 count=2 conv=notrunc本文永久更新連結地址：http://www.linuxidc.com/Linux/2017-05/144021.htm
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