Merging upstream version 1.17~rc1.

Signed-off-by: Daniel Baumann <mail@daniel-baumann.ch>

1 files changed, 75 insertions, 26 deletions

diff --git a/doc/lziprecover.info b/doc/lziprecover.info
index 6c636e8..05c1196 100644
--- a/doc/lziprecover.info
+++ b/doc/lziprecover.info
@@ -12,12 +12,13 @@ File: lziprecover.info,  Node: Top,  Next: Introduction,  Up: (dir)
 Lziprecover Manual
 ******************
 
-This manual is for Lziprecover (version 1.17-pre1, 16 October 2014).
+This manual is for Lziprecover (version 1.17-rc1, 21 January 2015).
 
 * Menu:
 
 * Introduction::           Purpose and features of lziprecover
 * Invoking lziprecover::   Command line interface
+* Data safety::            Protecting data from accidental loss
 * Repairing files::        Fixing bit-flip and similar errors
 * Merging files::          Fixing several damaged copies
 * File names::             Names of the files produced by lziprecover
@@ -28,7 +29,7 @@ This manual is for Lziprecover (version 1.17-pre1, 16 October 2014).
 * Concept index::          Index of concepts
 
 
-   Copyright (C) 2009-2014 Antonio Diaz Diaz.
+   Copyright (C) 2009-2015 Antonio Diaz Diaz.
 
    This manual is free documentation: you have unlimited permission to
 copy, distribute and modify it.
@@ -104,7 +105,7 @@ like lzip or lunzip.
 line of defense for the case where the backups are also damaged.
 
 
-File: lziprecover.info,  Node: Invoking lziprecover,  Next: Repairing files,  Prev: Introduction,  Up: Top
+File: lziprecover.info,  Node: Invoking lziprecover,  Next: Data safety,  Prev: Introduction,  Up: Top
 
 2 Invoking lziprecover
 **********************
@@ -252,20 +253,66 @@ invalid input file, 3 for an internal consistency error (eg, bug) which
 caused lziprecover to panic.
 
 
-File: lziprecover.info,  Node: Repairing files,  Next: Merging files,  Prev: Invoking lziprecover,  Up: Top
+File: lziprecover.info,  Node: Data safety,  Next: Repairing files,  Prev: Invoking lziprecover,  Up: Top
 
-3 Repairing files
+3 Protecting data from accidental loss
+**************************************
+
+There are 3 main types of data corruption that may cause data loss:
+single-byte errors, multi-byte errors (generally affecting a whole
+sector in a block device), and total device failure.
+
+   Lziprecover protects natively against single-byte errors (*note
+Repairing files::), as long as file integrity is checked frequently
+enough that a second single-byte error does not develop in the same
+member before the first one is repaired.
+
+   Lziprecover also protects against multi-byte errors (*note Merging
+files::), if at least one backup copy of the file is made.
+
+   The only remedy for total device failure is storing backup copies in
+separate media.
+
+   How does lzip compare with gzip and bzip2 with respect to data
+safety?  Lets suppose that you made a backup copy of your valuable
+scientific data, compressed it, and stored two copies on separate
+media. Years later you notice that both copies are corrupt.
+
+   If you compressed with gzip and both copies suffer any damage in the
+data stream, even if it is just one altered bit, the original data can't
+be recovered.
+
+   If you used bzip2, and if the file is large enough to contain more
+than one compressed data block (usually larger than 900 kB), and if no
+block is damaged in both files, then the data can be manually recovered
+by splitting the files with bzip2recover, verifying every block and then
+copying the right blocks in the right order in another file.
+
+   But if you used lzip, the data can be automatically recovered as
+long as no byte is damaged in both files.
+
+   Note that each error in a bzip2 file makes a whole block unusable,
+but each error in a lzip file only affects the damaged bytes, making it
+possible to recover a file with thousands of errors.
+
+
+File: lziprecover.info,  Node: Repairing files,  Next: Merging files,  Prev: Data safety,  Up: Top
+
+4 Repairing files
 *****************
 
 Lziprecover can repair perfectly most files with small errors (up to one
 single-byte error per member), without the need of any extra redundance
 at all. If the reparation is successful, the repaired file will be
-identical bit for bit to the original.
+identical bit for bit to the original. This makes lzip files resistant
+to bit-flip, one of the most common forms of data corruption.
 
    The error may be located anywhere in the file except in the header
 (first 6 bytes of each member) or in the 'Member size' field of the
-trailer (last 8 bytes of each member). This makes lzip files resistant
-to bit-flip, one of the most common forms of data corruption.
+trailer (last 8 bytes of each member). If the error is in the header it
+can be easily repaired with a text editor like GNU Moe (*note File
+format::). If the error is in the member size, it is enough to ignore
+the message about 'bad member size' when decompressing.
 
    Bit-flip happens when one bit in the file is changed from 0 to 1 or
 vice versa. It may be caused by bad RAM or even by natural radiation. I
@@ -289,7 +336,7 @@ lziprecover repairs more efficiently the worst errors.
 
 File: lziprecover.info,  Node: Merging files,  Next: File names,  Prev: Repairing files,  Up: Top
 
-4 Merging files
+5 Merging files
 ***************
 
 If you have several copies of a file but all of them are too damaged to
@@ -330,7 +377,7 @@ errors are randomly located inside each copy).
 
 File: lziprecover.info,  Node: File names,  Next: File format,  Prev: Merging files,  Up: Top
 
-5 Names of the files produced by lziprecover
+6 Names of the files produced by lziprecover
 ********************************************
 
 The name of the fixed file produced by '--merge' and '--repair' is made
@@ -341,7 +388,7 @@ original file name ends with one of the extensions '.tar.lz', '.lz' or
 
 File: lziprecover.info,  Node: File format,  Next: Examples,  Prev: File names,  Up: Top
 
-6 File format
+7 File format
 *************
 
 Perfection is reached, not when there is no longer anything to add, but
@@ -414,7 +461,7 @@ additional information before, between, or after them.
 
 File: lziprecover.info,  Node: Examples,  Next: Unzcrash,  Prev: File format,  Up: Top
 
-7 A small tutorial with examples
+8 A small tutorial with examples
 ********************************
 
 Example 1: Restore a regular file from its compressed version
@@ -485,7 +532,7 @@ correct file produced is saved in 'big_db_00001.lz'.
 
 File: lziprecover.info,  Node: Unzcrash,  Next: Problems,  Prev: Examples,  Up: Top
 
-8 Testing the robustness of decompressors
+9 Testing the robustness of decompressors
 *****************************************
 
 The lziprecover package also includes unzcrash, a program written to
@@ -562,8 +609,8 @@ caused unzcrash to panic.
 
 File: lziprecover.info,  Node: Problems,  Next: Concept index,  Prev: Unzcrash,  Up: Top
 
-9 Reporting bugs
-****************
+10 Reporting bugs
+*****************
 
 There are probably bugs in lziprecover. There are certainly errors and
 omissions in this manual. If you report them, they will get fixed. If
@@ -584,6 +631,7 @@ Concept index
 * Menu:
 
 * bugs:                                  Problems.              (line 6)
+* data safety:                           Data safety.           (line 6)
 * examples:                              Examples.              (line 6)
 * file format:                           File format.           (line 6)
 * file names:                            File names.            (line 6)
@@ -598,17 +646,18 @@ Concept index
 
 Tag Table:
 Node: Top231
-Node: Introduction1153
-Node: Invoking lziprecover4249
-Node: Repairing files9686
-Node: Merging files11371
-Node: File names13212
-Node: File format13676
-Node: Examples16183
-Ref: ddrescue-example17384
-Node: Unzcrash18493
-Node: Problems21047
-Node: Concept index21597
+Node: Introduction1216
+Node: Invoking lziprecover4312
+Node: Data safety9745
+Node: Repairing files11661
+Node: Merging files13563
+Node: File names15404
+Node: File format15868
+Node: Examples18375
+Ref: ddrescue-example19576
+Node: Unzcrash20685
+Node: Problems23239
+Node: Concept index23791
 
 End Tag Table