Provided by: myrescue_0.9.8-1_amd64 bug

NAME

       myrescue - Harddisc Rescue

SYNOPSIS

       myrescue  [-b block-size] [-B bitmap-file] [-A] [-S] [-r retry-count] [-f skip-failed] [-s
       start-block] [-e end-block] [-R] [-G good-range] [-F failed-range]  [-T]  [-J  jump-after-
       blocks] [-U usb-device-file] input-file output-file

DESCRIPTION

       myrescue  is  a  program  to rescue the still-readable data from a damaged harddisk. It is
       similar in purpose to dd_rescue, but it can be run in multiple passes and has  options  to
       avoid damaged areas to first handle the not yet damaged part of the disk.

       The  program  tries  to  copy  the  device  blockwise  to a file and keeps a table ("block
       bitmap") noting whether a block has been successfully copied, not yet handled or  has  had
       errors.  This  block  bitmap is used in successive passes to only read the not yet rescued
       blocks.

       The program has a special skip mode  to  handle  read  errors.  Usually  harddisk  surface
       defects  cover  more than just one block and continuous reading in defect areas can damage
       the surface, the heads and (by permanent  recalibration)  the  drive  mechanics.  If  this
       happens,  the  chances  of  rescuing the remaining undamaged data drop dramatically. So in
       skip mode, myrescue tries to get out of damaged areas quickly by exponentially  increasing
       the  stepsize.  The  skipped blocks are marked as unhandled in the block bitmap and can be
       retried later.

       As another alternative, the program can jump around on the disc, trying random  blocks  to
       first  get  an  overview  of the damage. In case of regular defects (e.g. an entire failed
       head) this can be used to determine the physical disc structure and to avoid these regions
       in the first run.

       Also there are options to avoid getting close to already recognized defects or stay in the
       proximity of good regions.

       Finally, the program has an option to multiply try to read a block before  considering  it
       damaged.

NOTE

       This tools is no replacement for a professional data recovery service!  If you do have the
       latter option, don't even think of using myrescue, as it may  further  damage  your  disk.
       This  tool  is provided only for the case that you are absolutely desperate and definitely
       cannot afford a professional data recovery and know what you are doing.

       Data recovery - whether professional or DIY - is always careful  detective  work.  Damaged
       drives  deteriorate  rapidly  and  behave  nondeterministically,  you may not get a second
       chance once you made a mistake. So you have to be fully aware of  what  you're  doing  and
       understand  precisely what's happening. If you are unsure it's probably best to stop right
       now and ask a linux guru for assistance.

       In any case do not expect too much. While  complete  restores  have  been  witnessed,  you
       should  not  take them for granted. A better attitude is to consider your data lost and be
       glad for any survivors that turn up.

       The usual GPL disclaimer applies. Especially the NON-WARRANTY OF FITNESS FOR A  PARTICULAR
       PURPOSE. Don't blame (or sue) me if it fails to recover or further damages your data.

       And  a  final  word  you  probably  don't  want  to hear in this situation: For the future
       consider a routinely backup to avoid a "next time".

OPTIONS

       -b block-size
              The  size  of  the  blocks  (in  bytes).  Set  this   to   your   harddiscs   error
              detection/correction  unit  size.  Usually  this  is  4096, which happens to be the
              default.

       -B bitmap-file
              The file containing the status table of all blocks.  Nice  (or  frightening...)  to
              view  with  hexdump.  01  means OK; 02 means that the block was OK, but took a long
              time to read; 00 means not yet done; negative values mean the number of failed read
              attempts. If not given, defaults to output-file.bitmap

       -A     Abort when encountering errors.

       -S     Activate  skip  mode:  When encountering errors increase the stepsize exponentially
              until a readable block is found.

       -f skip-failed
              Skip blocks that have already had skip-failed failures. Useful to avoid  scratching
              the same block over and over again.

       -r retry-count
              The  number  of  times to read a block before it is declared bad for this run. (You
              can still retry it on the next run.) Default: 1

       -s start-block
              The number of the block to start with. Default: 0

       -e end-block
              The number of the block, where reading stops (not  included!).   Default:  size  of
              input-file divided by block-size.

       -R     Reverse reading direction, i.e. from end-block (excluded) to start-block

       -G good-range
              Only  try to read blocks within good-range blocks from an already successfully read
              block.

       -F failed-range
              Extends -f to also skip any block within failed-range  blocks  of  a  block  to  be
              skipped as specified by -f.

       -T     Also  avoid blocks, that were successfully read, but took an unusually long time to
              read. In case of growing defects, these blocks can mark the boundaries of defective
              regions. This options makes -A, -S and -F treat such blocks as defective.

       -J jump-after-blocks
              Randomly  jump  across  the  disc  after  reading  jump-after-blocks blocks in both
              directions. This might be useful to scan discs with  scattered  defects.   In  jump
              mode -S causes myrescue to jump to a new block upon the first failed sector or upon
              hitting a sector to be skipped as specified by -f, -G or -F.

       -U usb-device-file
              (Linux-specific feature) Perform a bus  reset  for  the  specified  usb-device-file
              after every failed read attempt.  Certain faulty SD cards will disappear completely
              from the bus after a read  error  occurs  and  the  USB  reader  has  to  be  reset
              completely in order to continue.

       -h, -? Display usage information.

RECOMMENDED PROCEDURE

       NOTE:  In  data  recovery every case needs special consideration and a specific approach -
       mindlessly running procedures is a bad idea. So consider the following an example, keep  a
       close  eye  on  the  process  and  be  prepared to stop and reconsider if anything unusual
       happens. And once again: If you are feeling unsure, stop and ask someone  experienced  for
       assistance.

       ·      Make  sure  you  have sufficient disk space for twice the whole partition (complete
              partition size, not just the used amount of data) plus some  space  for  the  block
              bitmap (1 byte per block). Of course this should NOT be on the damaged disc.

       ·      Determine  the  hardware  block  size  (CRC/ECC unit) of your harddisk. This may be
              found out from hdparm, some entries in /proc/ide/hd? or on the web. I have not  yet
              checked whether this is possible with an ioctl. If you have, please let me know.

       ·      Start a skip mode run with one retry per block to first copy the undamaged area.

       ·      Start  a  normal run with one retry per block to copy the remaining skipped blocks.
              You may try to use -f 1 to skip the damaged blocks from the first run.

       ·      Repeat until the number of errors seems to have converged.  Try waiting a couple of
              hours between the retries.

       ·      Repeat this with higher retry counts and wait for convergence.

       ·      Make  a copy of the rescued data and run fsck on it. The copy is important! Running
              fsck is risky if blocks containing filesystem structures (superblocks, directories,
              inodes,  journal, ...) are missing. Sometimes the well-meant attempt to correct the
              filesystem can damage the image file, so always work on a copy.

       ·      Mount the filesystem (if copied to a file: via loopback) and check  your  data.  If
              directory  information has been destroyed, fsck moves unidentifiable file fragments
              to lost+found, so you should also check this location.

       It may help to try reading non-defect areas in between to allow the drive to recalibrate.

       The developers are  glad  to  hear  about  your  experiences.  Please  post  them  to  the
       Experiences forum on the Sourceforge Project page. Thank you!

KNOWN BUGS

       The  handling  of  the bitmap-file currently relies on the filesystem semantics, that when
       lseek(2) ing beyond the end of file and then writing, the space in between is filled  with
       zero-bytes.

       The block bitmap maxes out after 127 failed read attempts.

AUTHORS

       Kristof        Koehler        <kristofk@users.sourceforge.net>,       Peter       Schlaile
       <schlaile@users.sourceforge.net>

SEE ALSO

       dd(1), dd_rescue(no manpage?)

       http://www.google.de/search?q=data+recovery

       http://myrescue.sourceforge.net/