Linux中dd命令使用实例教程

   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 all

   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

   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)

  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

  dd if=/dev/hdb of=/dev/hdd

  dd if=/dev/hdb of=/root/image

  dd if=/dev/hdb | gzip > /root/image.gz

  #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

  #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 ~]$

  [oracle@rhel6 ~]$ dd if=2.sql of=1.sql bs=1k seek=1 count=2 conv=notrunc