I downloaded the firmware (.img) of my Android device (Boyue T62D) just to have a backup of it. I'm in the Indian countryside with an extremely limited internet connection, so this is a huge file for me. The reasons I'm unsure are:

  1. I can't extract the file (just to look at the contents) in any way on my computer (OS X 10.10.1). Is this to be expected with an Android image? I tried to unpack it using a variety of methods (like converting it to iso first). (none too fancy though).

  2. I was out of the house when the file was downloading, and when I came back it looked like the file was done, but the Internet connection was broken. But the file seems to have the same size as it is supposed to have. So what got me wondering was the fact that I can't unpack it. If you guys could just tell me that this is standard, and that .img files are very hard/impossible to extract on OS X, that would be great.

  • Where did you download the image from? Normally you get a file hash (MD5/SHA1) to verify exactly that. – Zonk Nov 5 '15 at 12:06
  • I downloaded it from here: [link] d-h.st/6cl [/link] How can I check whether I got a file hash? Also, is it normal that I'm unable to extract or convert the .img file using conventional apps? – Revetahw says Reinstate Monica Nov 5 '15 at 13:52
  • 4a575ab0e660a64630734645a1ef4231 that's the MD5 hash for the file. So open a terminal on Mac OSX, and run md5 <path-to-file> and compare the two values. What do you mean by "conventional apps"? What do you mean by converting the img file? Basically, what do you want to do? – Zonk Nov 5 '15 at 13:59
  • What I meant is that I tried to unpack the image, because if that worked, I figured it would mean that the file was ok. But I think the method you provided is a much better way of checking. I'll try it when I get home, I'm on my phone at the moment. – Revetahw says Reinstate Monica Nov 5 '15 at 14:57
  • Alright, I got the same MD5 hash. So this means my file is all good? Thanks. If you post this as an answer instead of a comment I can accept it. Also, how did you find the MD5 value? Did you download the file yourself and run the md5 in Terminal? Would I have been able to do this check without help from a third party with a normal internet connection? – Revetahw says Reinstate Monica Nov 5 '15 at 16:50

Usually when downloading files (very likely for software) you have a checksum provided by the supplier. The checksum is nothing else but the hash value of the file you're going to download. Quite often this is MD5, but due to the collision potential in MD5 it starts to drift towards SHA (SHA1 mostly, somtimes SHA2).

After your download has finished, you compute the hash on the file yourself and compare the value with the one presented by the download page (or other source). If the two values match, this means that your download equals the file supplied on the website.

I started my VM for accessing such sites and had a look if there is a MD5 hash present. Right next to the download link, it was and that's the value I have copied to my comment. Therefore, if you follow the procedure I have written down above and look for such a hash value (check for MD5 or MD5SUM, SHA1 or SHA1SUM) you don't need any third-party assistance.

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  • Cool, it's there on the download site. Just curious, do you use Virtual Machine every time you visit an unknown URL? – Revetahw says Reinstate Monica Nov 5 '15 at 17:09
  • Yes, it's there. No, not everytime. But with URLs that appear to be shortened, of those with bad ratings from sources like Google Safe Browsing etc. – Zonk Nov 5 '15 at 17:12
  • Alright. Thanks again. Is it not possible to upvote comments on this SE? – Revetahw says Reinstate Monica Nov 5 '15 at 17:15
  • Should be, just like answers – Zonk Nov 5 '15 at 17:59
  • My reputation is probably too low to upvote comments. – Revetahw says Reinstate Monica Nov 5 '15 at 18:00

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