lziprecover/README

Description

Lziprecover is a data recovery tool and decompressor for files in the
lzip compressed data format (.lz), able to repair slightly damaged
files, recover badly damaged files from two or more copies, extract data
from damaged files, decompress files and test integrity of files.

The lzip file format is designed for long-term data archiving. It is
clean, provides very safe 4 factor integrity checking, and is backed by
the recovery capabilities of lziprecover.

Lziprecover is able to recover or decompress files produced by any of
the compressors in the lzip family; lzip, plzip, minilzip/lzlib, clzip
and pdlzip.

Lziprecover makes lzip files resistant to bit-flip (one of the most
common forms of data corruption), and can safely merge multiple damaged
backup copies.

If the cause of file corruption is damaged media, the combination
GNU ddrescue + lziprecover is the best option for recovering data from
multiple damaged copies.

If a file is too damaged for lziprecover to repair it, all the
recoverable data in all members of the file can be extracted with the
'-D' option.

Lziprecover is able to efficiently extract a range of bytes from a
multi-member file, because it only decompresses the members containing
the desired data.

Lziprecover can print correct total file sizes and ratios even for
multi-member files.

When recovering data, lziprecover takes as arguments the names of the
damaged files and writes zero or more recovered files depending on the
operation selected and whether the recovery succeeded or not. The
damaged files themselves are never modified.

When decompressing or testing file integrity, lziprecover behaves like
lzip or lunzip.

To give you an idea of its possibilities, when merging two copies, each
of them with one damaged area affecting 1 percent of the copy, the
probability of obtaining a correct file is about 98 percent. With three
such copies the probability rises to 99.97 percent. For large files (a
few MB) with small errors (one sector damaged per copy), the probability
approaches 100 percent even with only two copies.

Lziprecover is not a replacement for regular backups, but a last line of
defense for the case where the backups are also damaged.

The lziprecover package also includes unzcrash, a program written to
test robustness to decompression of corrupted data, inspired by
unzcrash.c from Julian Seward's bzip2. Type 'make unzcrash' in the
lziprecover source directory to build it. Then try 'unzcrash --help'.


Copyright (C) 2009, 2010, 2011, 2012, 2013 Antonio Diaz Diaz.

This file is free documentation: you have unlimited permission to copy,
distribute and modify it.

The file Makefile.in is a data file used by configure to produce the
Makefile. It has the same copyright owner and permissions that configure
itself.