Zip gz recovery segments search process

Using PhotoRec to recover lost data
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dragon
Posts: 2
Joined: 07 Jun 2021, 02:49

Zip gz recovery segments search process

#1 Post by dragon »

Same dd reformat disaster as viewtopic.php?f=7&t=8265&p=26635&hilit=parts#p26635

trying to recover .gz (compressed iso) files. Used options to limit search to .gz

photorec found .gz files and .gz file segments

1) would photorec recover a large zip file - ie 18gb .gz file ? would photorec certainly recover segments of original zip file or will zip files be recovered all or none ? Would brute force mode in photorec change whether an 18gb file would be recovered in entirely or in a segmented way.

It seems like photorec will recover segments as it encounters them during search, but i am unclear if photorec sees parts inside large gz file or it sees parts of the gz file. If it does not see inside gz file then maybe it will recover all or none of a gz file if brute force is turned off.....?

2) Is it realistic to attempt to recover zipped iso files via photorec: unlike photos or .mov files which can loose a few bytes here and there but still generally look the same. if iso looses a few bytes it is likely not to function. This is my interest in the ability to "force" photorec to attempt to recover all or none of a .gz file

recuperation
Posts: 1592
Joined: 04 Jan 2019, 09:48
Location: Hannover, Deutschland (Germany, Allemagne)

Re: Zip gz recovery segments search process

#2 Post by recuperation »

dragon wrote: 07 Jun 2021, 04:58 Same dd reformat disaster as viewtopic.php?f=7&t=8265&p=26635&hilit=parts#p26635

trying to recover .gz (compressed iso) files.
.gz are not compressed iso files.

Used options to limit search to .gz

photorec found .gz files and .gz file segments

1) would photorec recover a large zip file - ie

I don' know what "ie" is.

18gb .gz file ? would photorec certainly recover segments of original zip file or will zip files be recovered all or none ?
Are you talking about gz oder zip?

Would brute force mode in photorec change whether an 18gb file would be recovered in entirely or in a segmented way.
Brute-force is not suitable for a file with a length of 18 GB.


It seems like photorec will recover segments as it encounters them during search, but i am unclear if photorec sees parts inside large gz file or it sees parts of the gz file. If it does not see inside gz file then maybe it will recover all or none of a gz file if brute force is turned off.....?
???!

2) Is it realistic to attempt to recover zipped iso files via photorec: unlike photos or .mov files which can loose a few bytes here and there but still generally look the same. if iso looses a few bytes it is likely not to function. This is my interest in the ability to "force" photorec to attempt to recover all or none of a .gz file
Please try to be precise!
On-disk fragmentation will determine if you succeed to recover the whole file correctly or only a part of it or a file containing a mix of your archive with one or other files.

dragon
Posts: 2
Joined: 07 Jun 2021, 02:49

Re: Zip gz recovery segments search process

#3 Post by dragon »

thank you recuperation for your reply. your answer about brute force not appropriate for a file 18gb, is very useful.

yes usually iso is not a gz file, but we use dd if=/dev/sdc1 | gzip > ub5sdc1.img.gz to shrink iso files for storage. It was the .img.gz files that were deleted by accident. This is why searching for .gz files.

if there is an option for recover all or none, then it will be easy to know if it makes sense to continue to try to recover the 16-18gb files deleted by accident.....if all of .gz file is not recoverable then the file is useless and no further attempts needed.

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