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How to split large (>4GB) ISO files for isostick


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#1 elegantinvention

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Posted 28 October 2012 - 04:33 AM

The ISO Manager software will do this for you! This guide is for those who wish to do it by hand :)

The isostick can only read files from FAT32 partitions. Unfortunately, FAT32 has a maximum file size of 4GB. To overcome this, isostick can read ISO files which are split into multiple parts, up to a maximum of 10 parts (so, 40GB is the maximum supported image size).
Requirements for ISO file parts:
  • Each part must only contain the ISO file data -- do not add any headers.
  • Each part's size must be evenly divisible by 2048bytes (the size of a CD/DVD sector).
  • Each part must use sequential extensions from .iso.0 thru a maximum of .iso.9
    For example if you are splitting a 6GB ISO named Win7x64.iso, you may end up with Win7x64.iso.0 (4GB) and Win7x64.iso.1 (2GB). Of course, you could also split it into two 3GB files, or any other combination, so long as the above limits are obeyed.
Users comfortable with the command line can use the split utility:
If you're on Windows you will need to get split from the GNU CoreUtils package. Linux and MacOS X should come with split.

split -a 1 -b 4000m -d blah.iso blah.iso.

Change "blah" to the name of the iso file, and be sure to keep that '.' at the end of the command!
Explanation of command-line options:
  • -a 1 Suffixes are only one character long
  • -b 4000m Maximum size of each file is 4000MB
  • -d Use numeric suffixes
Some split utilities do not support -d, for these you'll have to omit the -d option and it will produce files with extensions .iso.a, .iso.b, and so on. You will have to rename these to be numeric instead of alphabetical, or find a copy of split that supports the -d option.

For those uncomfortable with a command prompt: I haven't found a good free split utility that doesn't have its drawbacks, but here's a couple:
  • HJSplit does the job, but it is (at least in my testing) painfully slow.
    Also it will produce .iso.001, .iso.002, and so, which you will have to rename to .iso.0, .iso.1, etc.
    Just choose 'Split', and enter a split size of 4000 Mbytes.
  • HxD has an option under Extras -> File Tools -> Split, here's an example setup:
    Attached File  HxD-Split.png   23.1KB   15 downloads
    By choosing "Prompt for name" it will ask you for each filename, and you can specify the .iso.0, .iso.1, etc file extension for each. Set the size to 4000MB as shown.
If anyone is aware of other software options, please post below!

#2 steve6375

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Posted 28 October 2012 - 10:22 AM

I have made a small cmd file - if you unpack the zip file to a folder, you can just drag and drop any iso file onto the IsoSplit.cmd file and it will split it and then launch Explorer to select the first iso.0 file. I can't test it as I don't have an IsoStick...
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#3 Wonko the Sane

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Posted 28 October 2012 - 01:13 PM

Installing/downloading the gnu core utils for a simple "split" seems to me like overkill. :dubbio:
dsfo (part of the dsfok toolkit) or pldd (selfstanding) see here:
http://reboot.pro/15207/
would do , and writing a small batch to make use of either of them should be trivial.

But a one piece, simple tool, BOTH GUI and command line, and with the feature to join files too would be possibly "better":
http://www.jaist.ac....hoangle/filesj/
(but one needs a small batch to rename the .001, .002 to .0, .1, etc.)

The same can be done with sfk split:
http://stahlforce.co....php?tool=split

or (since we need a batch anyway) with sfk partcopy:
http://stahlforce.co...p?tool=partcopy

(the advantage being that the same tool exists in Win32, Linux and Mac
http://sourceforge.n...ileknife/1.6.6/

Can you define 4 Gb (in bytes)?

:cheers:
Wonko
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#4 elegantinvention

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Posted 29 October 2012 - 04:03 AM

@steve6375, just tested and it does indeed work, thanks! :yess:

Can you define 4 Gb (in bytes)?

As I'm sure you know, the FAT32 limit is 4GiB - 1byte (232-1 bytes), but the result must be evenly divisible by 2048bytes (CD/DVD sector size). So, the limit is floor((232-1) / 2048) = 4294965248 bytes. BUT, as long as it's under the FAT32 limit and some multiple of 2048bytes it'll work :)
Also thanks for the links :cheers:

#5 Wonko the Sane

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Posted 29 October 2012 - 12:07 PM

The question was less otiose that it seems at first sight, as always, people can stamp their feet and scream all the time they want, but a GB (a "real" GB, those that are"politically correct" now called GiB :whistling:) is made by 1,024x1,024x1,024=1,073,741,824 bytes.
4 of them make 4 x 1,073,741,824 = 4,294,967,296
The limit of the FAT32 is 1 byte less, hence 4,294,967,296-1=4,294,967,295

BUT, since the thingy is made of 2,048 bytes sector, the actual 4 Gb you initially mentioned is not 4 GB, but 4 GB-2,048, i.e. 4,294,967,296-2,048=4,294,965,248

Of course I knew the answer before asking the question ;), but I wanted to remark the vagueness of the initially stated 4GB :devil: .

Please also note how the 4000MB produced by the originally posted command can be (I havent' tested :ermm: ) actually 4,000x1,024x1,024 or 4,000x1,000x1,024, and thus, in any case, not 4,294,965,248.

Attached a small .cmd making use of FFSJ-Lite:
http://www.jaist.ac....hoangle/filesj/
http://www.jaist.ac....filesj/FFSJ.exe
and another one making use of DSFO part of the DSFOK toolkit:
http://members.ozema...eezip/freeware/
http://members.ozema...eware/dsfok.zip

as always, YMMV :hyper: .

:cheers:
Wonko

Attached Files


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#6 elegantinvention

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Posted 29 October 2012 - 12:25 PM

I thought you might be going there :whistling:
The 4000MiB is indeed not the maximum, but it is close enough, without having to remember any rather odd-looking and large numbers, and it meets the important part of being divisible by 2048 :heh:

The 1000 vs 1024 problem is such fun, isn't it? :crazy:

#7 Shawne Beeson

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Posted 07 February 2013 - 12:39 AM

Is there any way to work out the math if you have a ISO that is not perfectly even, I have a Windows Home Server Install DVD that is just a hair over the 4GB limit. If I just make one 4GB and the rest as the second disk, my second disk is not dividable by 2048



#8 elegantinvention

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Posted 07 February 2013 - 01:46 AM

@Shawne Beeson, what's the size of the original ISO in bytes? It should be divisible by 2048bytes, so you can just split it any which way that ends up with both parts being evenly divisible by 2048. By the way, if you're using Windows, you can just drop the ISO into ISO Manager and it'll split it for you, no maths required  :good:



#9 Shawne Beeson

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Posted 07 February 2013 - 02:22 AM

@Shawne Beeson, what's the size of the original ISO in bytes? It should be divisible by 2048bytes, so you can just split it any which way that ends up with both parts being evenly divisible by 2048. By the way, if you're using Windows, you can just drop the ISO into ISO Manager and it'll split it for you, no maths required  :good:

Ha, I thought I read that somewhere. Yea I could just split it in half, your right, I was thinking too hard. I will use ISO manager, Thanks alot for the quick reply.






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