ddrescue包装说明
像DD，dd_rescue从一个文件或块设备到另一台做复制数据。您可以指定文件的位置（称为寻求并跳过DD）。有几种不同：
- dd_rescue不提供的字符转换。
- 该命令的语法是不同的。呼叫dd_rescue -h。
- dd_rescue不上的错误中止输入文件，除非你指定一个最大的错误号。然后，当达到这个数字dd_rescue将中止。
- dd_rescue不会截断输出文件，除非要求。
- 你可以告诉dd_rescue从文件的末尾开始和向后移动。
- 它使用两个块大小，大的（软），块大小和小（硬）的块大小。在错误的情况下，规模回落到了小的，没有错误的一段时间后，再次提升。
资料来源：http://www.garloff.de/kurt/linux/ddrescue/
ddrescue首页 | 卡利ddrescue回购
- 作者：garloff
- 许可：GPL第二版
包含在ddrescue软件包工具
dd_rescue - 从一个文件或块设备复制到另一个数据
[email protected]:~# dd_rescue -h
dd_rescue Version 1.28, [email protected], GNU GPL
($Id: dd_rescue.c,v 1.130 2012/05/19 20:46:14 garloff Exp $)
(compiled Dec 15 2012 12:04:22 by gcc (Debian 4.7.2-4) 4.7.2)
(features: O_DIRECT splice )
dd_rescue copies data from one file (or block device) to another.
USAGE: dd_rescue [options] infile outfile
Options: -s ipos start position in input file (default=0),
-S opos start position in output file (def=ipos),
-b softbs block size for copy operation (def=65536, 1048576 for -d),
-B hardbs fallback block size in case of errs (def=4096, 512 for -d),
-e maxerr exit after maxerr errors (def=0=infinite),
-m maxxfer maximum amount of data to be transfered (def=0=inf),
-y syncfrq frequency of fsync calls on outfile (def=512*softbs),
-l logfile name of a file to log errors and summary to (def=""),
-o bbfile name of a file to log bad blocks numbers (def=""),
-r reverse direction copy (def=forward),
-t truncate output file (def=no),
-d/D use O_DIRECT for input/output (def=no),
-k use efficient in-kernel zerocopy splice
-w abort on Write errors (def=no),
-a spArse file writing (def=no),
-A Always write blocks, zeroed if err (def=no),
-i interactive: ask before overwriting data (def=no),
-f force: skip some sanity checks (def=no),
-p preserve: preserve ownership / perms (def=no),
-q quiet operation,
-v verbose operation,
-V display version and exit,
-h display this help and exit.
Sizes may be given in units b(=512), k(=1024), M(=1024^2) or G(1024^3) bytes
This program is useful to rescue data in case of I/O errors, because
it does not necessarily abort or truncate the output.dd_rescue用法示例
开始在输入文件的位置100（-s 100的/ var / log / messages中）和写 ，开始在目标文件（-S 0的/ tmp / ddrescue出）的位置0：
[email protected]:~# dd_rescue -s 100 /var/log/messages -S 0 /tmp/ddrescue-out
dd_rescue: (info): Using softbs=65536, hardbs=4096
dd_rescue: (info) expect to copy 1766kB from /var/log/messages
dd_rescue: (info): ipos: 1024.1k, opos: 1024.0k, xferd: 1024.0k
errs: 0, errxfer: 0.0k, succxfer: 1024.0k
+curr.rate: 1122807kB/s, avg.rate: 1018906kB/s, avg.load: 0.0%
>.......................-.................< 57% ETA: 0:00:00
dd_rescue: (info): read /var/log/messages (1767.0k): EOF
dd_rescue: (info): Summary for /var/log/messages -> /tmp/ddrescue-out:
dd_rescue: (info): ipos: 1767.0k, opos: 1767.0k, xferd: 1767.0k
errs: 0, errxfer: 0.0k, succxfer: 1767.0k
+curr.rate: 352945kB/s, avg.rate: 568151kB/s, avg.load: 0.0%
>.......................-................-< 100% ETA: 0:00:00