RECOVERDISK(1)

NAME
recoverdisk - recover data from hard disk or optical media

SYNOPSIS
recoverdisk [-b bigsize] [-r rlist] [-s snapshot] [-w wlist] special [file]

DESCRIPTION
The recoverdisk utility reads data from the special file until all blocks could be successfully read. It starts reading in multiples of the sector size. Whenever a block fails, it is put to the end of the working queue and will be read again, possibly with a smaller read size.

By default it uses block sizes of roughly 1 MB, 32kB, and the native sector size (usually 512 bytes). These figures are adjusted slightly, for devices whose sectorsize is not a power of 2, e.g., audio CDs with a sector size of 2352 bytes.

The options are as follows:

-b bigsize
    The size of reads attempted first. The middle pass is roughly the logarithmic average of the bigsize and the sectorsize.

-r rlist
    Read the list of blocks and block sizes to read from the specified file.

-s snapshot
    How often we should update the worklist file while things go OK. The default is 60 and the units is "progress messages" so if things go well, this is the same as once per minute.

-w wlist
    Write the list of remaining blocks to read to the specified file if recoverdisk is aborted via SIGINT.

The -r and -w options can be specified together. Especially, they can point to the same file, which will be updated on abort.

OUTPUT
The recoverdisk utility prints several columns, detailing the progress

start
    Starting offset of the current block.

size
    Read size of the current block.

len Length of the current block.

state
    Is increased for every failed read.

done
    Number of bytes already read.

remaining
    Number of bytes remaining.

% done
    Percent complete.

EXAMPLES

    # recover data from failing hard drive ad3
    touch /data/lots_of_space
    recoverdisk /dev/ad3 /data/lots_of_space
    # clone a hard disk
    recoverdisk /dev/ad3 /dev/ad4
    # read an ISO image from a CD-ROM
    touch /data/cd.iso; recoverdisk /dev/acd0 /data/cd.iso
    # continue reading from a broken CD and update the existing worklist
    recoverdisk -r worklist -w worklist /dev/acd0 /data/cd.iso
    # recover a single file from the unreadable media
    touch file.avi; recoverdisk /cdrom/file.avi file.avi
    # If the disk hangs the system on read-errors try:
    recoverdisk -b 0 /dev/ad3 /somewhere

SEE ALSO
dd(1)

HISTORY
The recoverdisk utility first appeared in FreeBSD 7.0.

AUTHORS
-nosplit The original implementation was done by Poul-Henning Kamp <phk@FreeBSD.org> with minor improvements from Ulrich Spörlein <uspoerlein@gmail.com>.

This manual page was written by Ulrich Spörlein.

BUGS
Reading from media where the sectorsize is not a power of 2 will make all 1 MB reads fail. This is due to the DMA reads being split up into blocks of at most 128kB. These reads then fail if the sectorsize is not a divisor of 128kB. When reading a full raw audio CD, this leads to roughly 700 error messages flying by. This is harmless.