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32 .Nd recover data from hard disk or optical media
44 utility reads data from the
46 file until all blocks could be successfully read.
47 It starts reading in multiples of the sector size.
48 Whenever a block fails, it is put to the end of the working queue and will be
49 read again, possibly with a smaller read size.
51 By default it uses block sizes of roughly 1 MB, 32kB, and the native
52 sector size (usually 512 bytes).
53 These figures are adjusted slightly, for devices whose sectorsize is not a
54 power of 2, e.g., audio CDs with a sector size of 2352 bytes.
56 The options are as follows:
57 .Bl -tag -width indent
59 The size of reads attempted first.
60 The middle pass is roughly the logarithmic average of the bigsize and
63 Read the list of blocks and block sizes to read from the specified file.
65 How often we should update the worklist file while things go OK.
66 The default is 60 and the units is "progress messages" so if things
67 go well, this is the same as once per minute.
69 Write the list of remaining blocks to read to the specified file if
79 options can be specified together.
80 Especially, they can point to the same file, which will be updated on abort.
85 prints several columns, detailing the progress
86 .Bl -tag -width remaining
88 Starting offset of the current block.
90 Read size of the current block.
92 Length of the current block.
94 Is increased for every failed read.
96 Number of bytes already read.
98 Number of bytes remaining.
104 # recover data from failing hard drive ad3
105 touch /data/lots_of_space
106 recoverdisk /dev/ad3 /data/lots_of_space
109 recoverdisk /dev/ad3 /dev/ad4
111 # read an ISO image from a CD-ROM
112 touch /data/cd.iso; recoverdisk /dev/acd0 /data/cd.iso
114 # continue reading from a broken CD and update the existing worklist
115 recoverdisk -r worklist -w worklist /dev/acd0 /data/cd.iso
117 # recover a single file from the unreadable media
118 touch file.avi; recoverdisk /cdrom/file.avi file.avi
120 # If the disk hangs the system on read-errors try:
121 recoverdisk -b 0 /dev/ad3 /somewhere
129 utility first appeared in
133 The original implementation was done by
134 .An Poul-Henning Kamp Aq phk@FreeBSD.org
135 with minor improvements from
136 .An Ulrich Sp\(:orlein Aq uspoerlein@gmail.com .
138 This manual page was written by
139 .An Ulrich Sp\(:orlein .
141 Reading from media where the sectorsize is not a power of 2 will make all
143 This is due to the DMA reads being split up into blocks of at most 128kB.
144 These reads then fail if the sectorsize is not a divisor of 128kB.
145 When reading a full raw audio CD, this leads to roughly 700 error messages