myrescue - Harddisc Rescue
] [-B bitmap-file
] [-r retry-count
] [-s start-block
] [-G good-range
] [-J jump-after-blocks
myrescue is a program to rescue the still-readable data from a damaged harddisk.
It is similar 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
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!
you do have the latter option, don't even think of using myrescue
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".
- -b block-size
- The size of the blocks (in bytes). Set this to your
harddisks 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; 00 means not yet
done; negative values mean the number of failed read attempts. If not
given, defaults to output-file.bitmap
- Abort when encountering errors.
- 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
- -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:
- -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
- 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
- -J jump-after-blocks
- 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 amount 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 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
- 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
The developers are glad to hear about your experiences. Please post them to the
forum on the Sourceforge Project page. Thank you!
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 <firstname.lastname@example.org>, Peter Schlaile