Provided by: par2_0.4-11build1_amd64 bug


       par2 - PAR 2.0 compatible file verification and repair tool.


       par2 c(reate) [options] <par2 file> [files]
       par2 v(erify) [options] <par2 file> [files]
       par2 r(epair) [options] <par2 file> [files]


       par2create [options] <par2 file> [files]
       par2verify [options] <par2 file> [files]
       par2repair [options] <par2 file> [files]


       par2  is  a  program  for creating and using PAR2 files to detect damage in data files and
       repair them if necessary. It can be used with any kind of file.


       -b<n>  Set the Block-Count

       -s<n>  Set the Block-Size (Don't use both -b and -s)

       -r<n>  Level of Redundancy (%)

       -c<n>  Recovery block count (don't use both -r and -c)

       -f<n>  First Recovery-Block-Number

       -u     Uniform recovery file sizes

       -l     Limit size of recovery files (Don't use both -u and -l)

       -n<n>  Number of recovery files (Don't use both -n and -l)

       -m<n>  Memory (in MB) to use

       -v [-v]
              Be more verbose

       -q [-q]
              Be more quiet (-qq gives silence)

       --     Treat all remaining CommandLine as filenames


       With PAR 2.0 you can create PAR2 recovery files for as few as 1 or as many as 32768 files.
       If  you wanted to create PAR1 recovery files for a single file you are forced to split the
       file into muliple parts and RAR is frequently used for this purpose. You do  NOT  need  to
       split files with PAR 2.0.

       To  create PAR 2 recovery files for a single data file (e.g. one called test.mpg), you can
       use the following command:

         par2 create test.mpg

       If test.mpg is an 800 MB file, then this will create a total of  8  PAR2  files  with  the
       following filenames (taking roughly 6 minutes on a PC with a 1500MHz CPU):

         test.mpg.par2      - This is an index file for verification only
         test.mpg.vol00+01.par2 - Recovery file with 1 recovery block
         test.mpg.vol01+02.par2 - Recovery file with 2 recovery blocks
         test.mpg.vol03+04.par2 - Recovery file with 4 recovery blocks
         test.mpg.vol07+08.par2 - Recovery file with 8 recovery blocks
         test.mpg.vol15+16.par2 - Recovery file with 16 recovery blocks
         test.mpg.vol31+32.par2 - Recovery file with 32 recovery blocks
         test.mpg.vol63+37.par2 - Recovery file with 37 recovery blocks

       The test.mpg.par2 file is 39 KB in size and the other files vary in size from 443 KB to 15

       These par2 files will enable the recovery of up to 100 errors totalling 40 MB of  lost  or
       damaged  data  from  the  original  test.mpg file when it and the par2 files are posted on

       When posting on UseNet it is recommended that you use the "-s" option to set  a  blocksize
       that  is  equal to the Article size that you will use to post the data file. If you wanted
       to post the test.mpg file using an article size of 300 KB then the command you would  type

         par2 create -s307200 test.mpg

       This  will  create 9 PAR2 files instead of 8, and they will be capable of correcting up to
       134 errors totalling 40 MB. It will take roughly 8 minutes to create  the  recovery  files
       this time.

       In  both  of  these  two  examples,  the total quantity of recovery data created was 40 MB
       (which is 5% of 800 MB). If you wish to create a greater or lesser  quantity  of  recovery
       data, you can use the "-r" option.

       To  create  10% recovery data instead of the default of 5% and also to use a block size of
       300 KB, you would use the following command:

         par2 create -s307200 -r10 test.mpg

       This would also create 9 PAR2 files, but they would be able to correct up  to  269  errors
       totalling  80  MB.  Since  twice  as  much recovery data is created, it will take about 16
       minutes to do so with a 1500MHz CPU.

       The "-u" and "-n" options can be used to control  exactly  how  many  recovery  files  are
       created and how the recovery blocks are distributed amoungst them.  They do not affect the
       total quantity of recovery data created.

       The "-f" option is used when you create additional recovery data.

       e.g. If you have already created 10% and want another 5% then you migh use  the  following

         par2 create -s307200 -r5 -f300 test.mpg

       This specifies the same block size (which is a requirement for additional recovery files),
       5% recovery data, and a first block number of 300.

       The "-m" option controls how much memory par2 uses.  It  defaults  to  16  MB  unless  you
       override it.


       When  creating  PAR2  recovery  files  form multiple data files, you must specify the base
       filename to use for the par2 files and the names of all of the data files.

       If test.mpg had been split into multiple RAR files, then you could use:

         par2 create test.mpg.rar.par2 test.mpg.part*.rar

       The files filename "test.mpg.rar.par2" says what you want the par2 files to be called  and
       "test.mpg.part*.rar" should select all of the RAR files.


       When  using  par2  recovery  files to verify or repair the data files from which they were
       created, you only need to specify the filename of one of the par2 files to par2.


         par2 verify test.mpg.par2

       This tells par2 to use the information in test.mpg.par2 to verify the data files.

       par2 will automatically search for the other par2 files that  were  created  and  use  the
       information they contain to determine the filenames of the original data files and then to
       verify them.

       If all of the data files are ok, then par2 will report that repair will not be required.

       If any of the data files are missing or damaged, par2 will report the details of  what  it
       has  found. If the recovery files contain enough recovery blocks to repair the damage, you
       will be told that repair is possible. Otherwise you will be told exactly how many recovery
       blocks will be required in order to repair.

       To carry out a repair use the following command:

         par2 repair test.mpg.par2

       This tells par2 to verify and if possible repair any damaged or missing files. If a repair
       is carried out, then each file which is repaired will be re-verified to confirm  that  the
       repair was successful.


       If  any  of  the  recovery files or data files have the wrong filename, then par2 will not
       automatically find and scan them.

       To have par2 scan such files, you must include them on the command line when attempting to
       verify or repair.


         par2 r test.mpg.par2 other.mpg

       This tells par2 to scan the file called other.mpg to see if it contains any data belonging
       to the original data files.

       If one of the extra files specified in this way is an exact match for a  data  file,  then
       the repair process will rename the file so that it has the correct filename.

       Because par2 is designed to be able to find good data within a damaged file, it can do the
       same with incomplete files downloaded from UseNet. If some of the articles for a file  are
       missing,  you  should still download the file and save it to disk for par2 to scan. If you
       do this then you may find that you can carry out a repair in a situation where  you  would
       not otherwise have sufficient recovery data.

       You  can  have  par2 scan all files that are in the current directory using a command such

         par2 r test.mpg.par2 *


       If par2 determines that any of the data files are damaged or missing and finds that  there
       is insufficient recovery data to effect a repair, you will be told that you need a certain
       number of recovery blocks. You can obtain these by downloading additional recovery files.

       In order to make things easy, par2 files have filenames that tell  you  exactly  how  many
       recovery blocks each one contains.

       Assuming that the following command was used to create recovery data:

         par2 c -b1000 -r5 test.mpg

       Then the recovery files that are created would be called:


       The  first  file  in  this  list  does  not  contain  any  recovery data, it only contains
       information sufficient to verify the data files.

       Each of the other files contains a different number of recovery blocks.  The number  after
       the '+' sign is the number of recovery blocks and the number preceding the '+' sign is the
       block number of the first recovery block in that file.

       If  par2  told  you  that  you  needed  10  recovery   blocks,   then   you   would   need
       "test.mpg.vol01+02.par2"  and "test.mpg.vol07+08.par". You might of course choose to fetch
       "test.mpg.vol15+16.par2" instead (in which case you would have an extra 6 recovery  blocks
       which would not be used for the repair).


       This version of par2 does not support recording path information for files. Whilst you can
       create recovery files for files from multiple locations, it will expect all files to be in
       the  current  directory when verifying and repairing. This limitation will be corrected in
       an update.


       PAR2 uses Reed Solomon Coding to perform its calculations.  For  details  of  this  coding
       technique try the following link:

       ``A   Tutorial   on   Reed-Solomon  Coding  for  Fault-Tolerance  in  RAID-like  Systems''


       par2 was written by Peter Brian Clements <>.

       This man page was contributed  by  Andres  Salomon  <>  for  the  Debian
       GNU/Linux system (but may be used by others).

                                             May 2004                                     par2(1)