Opening .rar files

[Robin Laing]

Michael Wiktowy wrote:
> On 10/29/07, Robin Laing <Robin.Laing at drdc-rddc.gc.ca> wrote:
>> I would love an open source program that does what RAR files do.  With
>> the addition of PAR2 files, the RAR files or compressed files can be
>> repaired.
> 
> ...
> 
>> The problem is RAR is used heavily in usenet.  RAR is not only a
>> compression tool but a splitter and a great archiving tool.
>>
>> FWIW, there is a rpm "par2cmdline" that generates and works with par2
>> files.  This is part of Fedora.
> 
>>From what I have read about rar, all the rar pieces are simply one
> archive that has been binary chopped up into n pieces. You can do that
> with any archive with the "split" command and then "cat" them back
> together. I have done that to chop up a large disk image to avoid the
> 2GB/file limit on FAT32 external backup drives:
> 
> dd if=/dev/partition_to_be_read_from | gzip -c \
> | split -b 2000m - /mnt/usb/image_name.img.gz.
> 
> Then to combine them:
> 
> cat /mnt/usb/image_name.img.gz.* \
> | gzip -dc | dd of=/dev/partition_to_be_written_to
> 
> /Mike
> 

True but rar will also create parity blocks to check and repair the 
split files.

As I understand it, RAR is a form of RAID for archiving files on 
different media.  It then started getting used on usenet for sending 
large bin files.  Vary useful as you can check and repair the files.

 From http://en.wikipedia.org/wiki/RAR_(file_format)

"Variable amounts of redundancy (“recovery record”) can be added to an 
archive, making it more resistant to corruption. Even if parts of an 
archive are damaged, it is possible to fully recover the stored data if 
a large enough recovery record exists."

Can this be done with gz?

Of course a gz file could be run through par2 and have redundancy blocks 
created.  I guess this could then be done with any file allowing pgp 
encrypted files to be repaired.



-- 
Robin Laing