freebsd/sbin/recoverdisk/recoverdisk.1

.\" Copyright (c) 2006 Ulrich Spoerlein <uspoerlein@gmail.com>
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" $FreeBSD$
.\"
.Dd January 5, 2012
.Dt RECOVERDISK 1
.Os
.Sh NAME
.Nm recoverdisk
.Nd recover data from hard disk or optical media
.Sh SYNOPSIS
.Nm
.Op Fl b Ar bigsize
.Op Fl r Ar readlist
.Op Fl s Ar interval
.Op Fl w Ar writelist
.Ar source
.Op Ar destination
.Sh DESCRIPTION
The
.Nm
utility reads data from the
.Ar source
file until all blocks could be successfully read.
If
.Ar 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.
.Pp
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.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl b Ar bigsize
The size of reads attempted first.
The middle pass is roughly the logarithmic average of the bigsize and
the sectorsize.
.It Fl r Ar readlist
Read the list of blocks and block sizes to read from the specified file.
.It Fl s Ar 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.
.It Fl w Ar writelist
Write the list of remaining blocks to read to the specified file if
.Nm
is aborted via
.Dv SIGINT .
.El
.Pp
The
.Fl r
and
.Fl w
options can be specified together.
Especially, they can point to the same file, which will be updated on abort.
.Sh OUTPUT
The
.Nm
utility
prints several columns, detailing the progress
.Bl -tag -width remaining
.It Va start
Starting offset of the current block.
.It Va size
Read size of the current block.
.It Va len
Length of the current block.
.It Va state
Is increased for every failed read.
.It Va done
Number of bytes already read.
.It Va remaining
Number of bytes remaining.
.It Va "% done"
Percent complete.
.El
.Sh EXAMPLES
.Bd -literal
# recover data from failing hard drive ad3
recoverdisk /dev/ad3 /data/disk.img

# clone a hard disk
recoverdisk /dev/ad3 /dev/ad4

# 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/ad3 /somewhere

.Ed
.Sh SEE ALSO
.Xr dd 1 ,
.Xr ada 4,
.Xr cam 4,
.Xr cd 4,
.Xr da 4
.Sh HISTORY
The
.Nm
utility first appeared in
.Fx 7.0 .
.Sh AUTHORS
.An -nosplit
The original implementation was done by
.An Poul-Henning Kamp Aq phk@FreeBSD.org
with minor improvements from
.An Ulrich Sp\(:orlein Aq uqs@FreeBSD.org .
.Pp
This manual page was written by
.An Ulrich Sp\(:orlein .
.Sh 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
.Fl b
to no more than 128kB.
.Pp
.Nm
needs to know about read errors as fast as possible, i.e. retries by lower
layers will usually slow down the operation.
When using
.Xr cam 4
attached drives, you may want to set kern.cam.XX.retry_count to zero, e.g.:
.Bd -literal
# sysctl kern.cam.ada.retry_count=0
# sysctl kern.cam.cd.retry_count=0
# sysctl kern.cam.da.retry_count=0
.Ed
.\".Pp
.\"When reading from optical media, a bug in the GEOM framework will
.\"prevent it from seeing that the media has been removed.
.\"The device can still be opened, but all reads will fail.
.\"This is usually harmless, but will send
.\".Nm
.\"into an infinite loop.