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To open the TAR archive on my PC, I have to rename the .tar.a to .tar, otherwise my archive manager will say "Archive type unsupported" or similar.

Why do they do that, and how to open these archives in a proper way?

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up vote 9 down vote accepted

It does this in order to break up large .tar files into chunks of 1000000000 bytes (or 1 GB):

-rwxrwx--- root     sdcard_r          0 2014-03-19 14:31 data.ext4.tar
-rwxrwx--- root     sdcard_r 1000000000 2014-03-19 14:33 data.ext4.tar.a
-rwxrwx--- root     sdcard_r 1000000000 2014-03-19 14:36 data.ext4.tar.b
-rwxrwx--- root     sdcard_r 1000000000 2014-03-19 14:38 data.ext4.tar.c
-rwxrwx--- root     sdcard_r  135127040 2014-03-19 14:38 data.ext4.tar.d

Even if the resulting file is under the 1000000000-byte split limit, the .a file will still be generated:

-rwxrwx--- root     sdcard_r         0 2014-03-19 14:29 system.ext4.tar
-rwxrwx--- root     sdcard_r 484504064 2014-03-19 14:30 system.ext4.tar.a

You can combine these split files back together using the following syntax:

On Windows: copy /b finelame* filename E.g. copy /b data.ext4.tar* data.ext4.tar
On Linux: cat filename* > filename E.g. cat data.ext4.tar* > data.ext4.tar

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Thanks, good answer but why is .tar always zero? – user42276 Mar 27 '14 at 18:52
Not sure off the top of my head, I'd have to look into CWM code. It's probably a placeholder for the original file name. – Chahk Mar 27 '14 at 18:57
You sir disearve every single internet prizes and nominations. You have just saved my life (and my contacts list) for I didn't know how to put those .a .b .c and the zero-ed rar file together. For the question about the 0kb .rar, during the cmd (which I recomend runing trough the folder using SHIFT+right click > open command window here) every chunk of tar file will be copied towards the zero-ed rar file. Thanks again bud. – user60304 May 9 '14 at 2:35

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