08-31-2009
if : input file
of : output file
ibs : tell how many bytes to read at a time, something like block size
count: read those blocks for maximum of this times,
so
# dd if=infile ibs=N count=M of=outfile
Will work if N * M = 48
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LEARN ABOUT DEBIAN
ddrescue
DDRESCUE(1) User Commands DDRESCUE(1)
NAME
ddrescue - data recovery tool
SYNOPSIS
ddrescue [options] infile outfile [logfile]
DESCRIPTION
GNU ddrescue - Data recovery tool. Copies data from one file or block device to another, trying hard to rescue data in case of read
errors.
You should use a logfile unless you know what you are doing.
OPTIONS
-h, --help
display this help and exit
-V, --version
output version information and exit
-a, --min-read-rate=<bytes>
minimum read rate of good areas in bytes/s
-A, --try-again
mark non-split, non-trimmed blocks as non-tried
-b, --block-size=<bytes>
sector size of input device [default 512]
-B, --binary-prefixes
show binary multipliers in numbers [SI]
-c, --cluster-size=<sectors>
sectors to copy at a time [128]
-C, --complete-only
do not read new data beyond logfile limits
-d, --direct
use direct disc access for input file
-D, --synchronous
use synchronous writes for output file
-e, --max-errors=[+]<n>
maximum number of [new] error areas allowed
-E, --max-error-rate=<bytes>
maximum allowed rate of read errors per second
-f, --force
overwrite output device or partition
-F, --fill=<types>
fill given type blocks with infile data (?*/-+)
-g, --generate-logfile
generate approximate logfile from partial copy
-i, --input-position=<bytes>
starting position in input file [0]
-I, --verify-input-size
verify input file size with size in logfile
-K, --skip-size=<bytes>
initial size to skip on read error [64 KiB]
-m, --domain-logfile=<file>
restrict domain to finished blocks in file
-M, --retrim
mark all failed blocks as non-trimmed
-n, --no-split
do not try to split or retry failed blocks
-o, --output-position=<bytes>
starting position in output file [ipos]
-p, --preallocate
preallocate space on disc for output file
-q, --quiet
suppress all messages
-r, --max-retries=<n>
exit after given retries (-1=infinity) [0]
-R, --reverse
reverse direction of copy operations
-s, --max-size=<bytes>
maximum size of input data to be copied
-S, --sparse
use sparse writes for output file
-t, --truncate
truncate output file to zero size
-T, --timeout=<interval>
maximum time since last successful read
-v, --verbose
be verbose (a 2nd -v gives more)
-x, --extend-outfile=<bytes>
extend outfile size to be at least this long
Numbers may be followed by a multiplier: b = blocks, k = kB = 10^3 = 1000, Ki = KiB = 2^10 = 1024, M = 10^6, Mi = 2^20, G = 10^9, Gi =
2^30, etc... Time intervals have the format 1[.5][smhd] or 1/2[smhd].
REPORTING BUGS
Report bugs to bug-ddrescue@gnu.org
Ddrescue home page: http://www.gnu.org/software/ddrescue/ddrescue.html
General help using GNU software: http://www.gnu.org/gethelp
COPYRIGHT
Copyright (C) 2012 Antonio Diaz Diaz. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
The full documentation for ddrescue is maintained as a Texinfo manual. If the info and ddrescue programs are properly installed at your
site, the command
info ddrescue
should give you access to the complete manual.
ddrescue 1.16 June 2012 DDRESCUE(1)