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Last updated on 2008-01-11.
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par2 create -r10 test.mpg par2 create -r10 stws1-vertigo.par2 stws1-vertigo.*
-u Uniform recovery file sizes
par2cmdline 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.
WHY IS PAR 2.0 better than PAR 1.0?
Yes, there is one dissadvantage:
This dissadvantage is considerably mitigated by the fact that you don't need to create as much recovery data in the first place to provide the same level of protection against loss and damage.
par2 c(reate) [options] <par2 file> [files] par2 v(erify) [options] <par2 file> [files] par2 r(epair) [options] <par2 file> [files]
Also:
par2create [options] <par2 file> [files] par2verify [options] <par2 file> [files] par2repair [options] <par2 file> [files]
Options:
-b<n> : Set the Block-Count -s<n> : Set the Block-Size -r<n> : Level of Redundancy (%) -m<n> : Memory (in MB) to use -- : 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.
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 MB.
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 UseNet.
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 (recommended to be the same as the posting article size), you would use the following command:
par2 create -s307200 -r10 test.mpg
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.
par2 verify test.mpg.par2
This tells par2cmdline to use the information in test.mpg.par2 to verify the data files.
par2cmdline 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 par2cmdline will report that repair will not be required.
If any of the data files are missing or damaged, par2cmdline 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 par2cmdline 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 par2cmdline 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.
For the following recovery files,
test.mpg.par2 test.mpg.vol00+01.par2 test.mpg.vol01+02.par2 test.mpg.vol03+04.par2 test.mpg.vol07+08.par2 test.mpg.vol15+16.par2 test.mpg.vol31+19.par2
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; the
number preceding the "`" sign is the block number of the first recovery
block in that file.
If par2cmdline 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 par2cmdline 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.