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RECOVERDISK(1) FreeBSD General Commands Manual RECOVERDISK(1)
NAME
recoverdisk - recover data from hard disk or optical media
SYNOPSIS
recoverdisk [-b bigsize] [-r readlist] [-s interval] [-u pattern] [-v]
[-w writelist] source [destination]
DESCRIPTION
The recoverdisk utility reads data from the source file until all blocks
could be successfully read. If destination was specified all data is
being written to that file. 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 readlist
Read the list of blocks and block sizes to read from the
specified file.
-s interval
How often we should update the writelist file while things go OK.
The default is 60 and the unit is "progress messages" so if
things go well, this is the same as once per minute.
-u pattern
By default blocks which encounter read errors will be filled with
the pattern `_UNREAD_' in the output file. This option can be
used to specify another pattern. Nothing gets written if the
string is empty.
-v Enables nicer status report using ANSI escapes and UTF-8.
-w writelist
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.
% done Percent complete.
EXAMPLES
# recover data from failing hard drive ada3
recoverdisk /dev/ada3 /data/disk.img
# clone a hard disk
recoverdisk /dev/ada3 /dev/ada4
# read an ISO image from a CD-ROM
recoverdisk /dev/cd0 /data/cd.iso
# continue reading from a broken CD and update the existing worklist
recoverdisk -r worklist -w worklist /dev/cd0 /data/cd.iso
# recover a single file from the unreadable media
recoverdisk /cdrom/file.avi file.avi
# If the disk hangs the system on read-errors try:
recoverdisk -b 0 /dev/ada3 /somewhere
SEE ALSO
dd(1), ada(4), cam(4), cd(4), da(4)
HISTORY
The recoverdisk utility first appeared in FreeBSD 7.0.
AUTHORS
The original implementation was done by Poul-Henning Kamp
<phk@FreeBSD.org> with minor improvements from Ulrich Sporlein
<uqs@FreeBSD.org>.
This manual page was written by Ulrich Sporlein.
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 and can be
avoided by setting -b to no more than 128kB.
recoverdisk needs to know about read errors as fast as possible, i.e.,
retries by lower layers will usually slow down the operation. When using
cam(4) attached drives, you may want to set kern.cam.XX.retry_count to
zero, e.g.:
# sysctl kern.cam.ada.retry_count=0
# sysctl kern.cam.cd.retry_count=0
# sysctl kern.cam.da.retry_count=0
FreeBSD 14.0-RELEASE-p11 April 3, 2020 FreeBSD 14.0-RELEASE-p11