[mythtv-users] Recovering recordings from corrupted partition

Torsten Crass torsten.crass at bioinf.med.uni-goettingen.de
Mon Dec 8 08:29:09 UTC 2008


Ian, James,

> dd can be a major source of pain. :( If it's any consolation we've all done
> it at some point. ;)

*g* "learning through pain", that is!

> Once you've finished recovering the drive, before you finally format it it
> /might/ be worth running mkfs.ext3 with the -S option, then fscking the
[...]
> Because the filesystem is ext3 you can try to recover based on a backup
> superblock. man e2fsck and look at the '-b' option.

This is something I also came up with after doing some own research 
(somehow I didn't manage to check back in the forum for quite a while) 
-- seemed reasonable since I only overwrote about 2% of the original 
file system, so there should be quite some alternative superblocks left. 
I used the "testdisk" tool to find one that was clearly beyond the 
corrupted part and run e2fsck with the corresponding -b option. Of 
course, loads of errors were reported, and when the "healing" process 
was still in progress after 5 days, I decided to just say goodby to my 
recordings and re-formatted the disk. (Fortunately, most programmes get 
frequently repeated on German TV... ;-)

Just another observation I found quite interesting: After re-installing 
MythTV, I run the shell script I initially posted on some new 
recordings, and it seemed to me that those DVB-T-derived mpg files do 
indeed exhibit byte patterns in their beginning which are different from 
the mpg header definition found in e.g. the "foremost" config file. 
Furthermore, I couldn't identify any common byte patterns within the 
last approx. 64k of those files, so that header-footer-based recovery 
methods most likely wouldn't have worked anyway.

Thanks to all of you, and best regards --

	Torsten


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