myrescue - Harddisc Rescue
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] [-J jump-after-blocks] input-file output-file
myrescue is a program to rescue the still-readable data from a damaged
harddisk. It is similiar in purpose to dd_rescue, but it tries to
quickly get out of damaged areas to first handle the not yet damaged
part of the disk and return later.
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 can be
used in successive runs to concentrate on 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.
Finally, the program has an option to multiply try to read a block
before considering it damaged.
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. Or in case you know what you are doing,
e.g. if you know that it is the aging of the magnetisation layer that
is causing your problem.
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".
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.
The file containing the status table of all blocks. Nice (or
frightening...) to view with hexdump. 01 means OK; 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.
Skip blocks that have already had skip-failed failures. Useful
to avoid scratching the same block over and over again.
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:
The number of the block to start with. Default: 0
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
Only try to read blocks within good-range blocks from an already
successfully read block.
Extends -f to also skip any block within failed-range blocks of
a block to be skipped as specified by -f.
Randomly jump across the disc after reading jump-after-blocks
blocks. 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.
-h, -? Display usage information.
· Make sure you have sufficient disk space to copy the whole
partition (not just the used ammount of data) to plus some space
for the block bitmap (1 byte per block).
· 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
· 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.
· 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
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 overflows after 128 failed read attempts.
Kristof Koehler <email@example.com>, Peter Schlaile
dd(1), dd_rescue(no manpage?)