.img-Format

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michael
Posts: 2
Joined: Tue Sep 02, 2014 1:30 pm

.img-Format

Post by michael »

Alex,

we are currently working on the digital preservation of USB sticks and have therefore used your brilliant imaging tool, what worked really good.

Because we want to keep the imaged files for the long term, we are wondering, which format the ".img" exactly is and how we maybe could identify it - do you have any information on this or a detailed specification about the used format?

Thanks in advance end all bests
Michael
Alex
Site Admin
Posts: 267
Joined: Fri Jul 29, 2011 11:59 pm

Re: .img-Format

Post by Alex »

The img format is a a raw format with no further specific information. It contains the whole available data on a flash drive (in device mode) or volume (in volume mode) regardless the used partitions or file systems. You can find more infos here:

http://en.wikipedia.org/wiki/IMG_%28file_format%29
michael
Posts: 2
Joined: Tue Sep 02, 2014 1:30 pm

Re: .img-Format

Post by michael »

Alex,

thanks a lot for your fast response, which helps a lot.

But as you might now, for us as digital archivists it is really important to identify and to border archived format. And because .img is also used for other formats we try to collect information how to identify it clearly.

Thanks again!

Michael
Alex
Site Admin
Posts: 267
Joined: Fri Jul 29, 2011 11:59 pm

Re: .img-Format

Post by Alex »

As I tried to explain, img is no file format itself. It is just a binary representation of all data with no further control information. The data in an img file will contain the partition information and various file systems in these partitions. These might be for example FAT, NTFS, ext2.

For you as an archivist it would be important to have the opportunity to open or restore the images back to a device and also have a device, that is able to read these file systems. The FAT file system for example was introduced 1978 and was widely spread together with MS-DOS. It's still supported by most operating systems (Windows, Linux, ...).

What you could do is to test, if your img file has a valid MBR or boot sector. Best way to do this is to check byte position 0x1FE in the image file. Bytes 511 and 512 must contain the magic bytes 0x55 0xAA. Please also see the following Wikipedia entries:

http://en.wikipedia.org/wiki/Master_boot_record
http://en.wikipedia.org/wiki/File_Allocation_Table
http://en.wikipedia.org/wiki/Design_of_ ... Bootsector
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