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I have an installer file 6GB in size, and I need to burn it to DVD, but I only have single layer (4.7GB capacity) media.

How can I split this big file into pieces that will fit on my media?

I am thinking of making an ISO, is this the correct approach?

I only want free or open source solution please.

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2 Answers

up vote 4 down vote accepted

Using terminal, you can split a file into chunks of the size of your choice.

These chunks can be then stitched back together again quite easily. This allows you to spread a large file over a number of CDs/DVDs, or more often floppy discs back in the day when this was more of an issue.

In the following example I have an ISO file of approximately 50Mb, that I split into 25Mb chunks. I then stitched them back together again under a new name and checksummed them to prove they remain identical:

StuffeMac:tmp stuffe$ ls -l
total 99328
-rwxr-xr-x@ 1 stuffe  staff  50855936  3 May 09:30 ocz_tools_316.iso
StuffeMac:tmp stuffe$ split -b 25m ocz_tools_316.iso
StuffeMac:tmp stuffe$ ls -l
total 198656
-rwxr-xr-x@ 1 stuffe  staff  50855936  3 May 09:30 ocz_tools_316.iso
-rw-r--r--  1 stuffe  staff  26214400  3 May 09:32 xaa
-rw-r--r--  1 stuffe  staff  24641536  3 May 09:32 xab
StuffeMac:tmp stuffe$ cat x* > new.iso
StuffeMac:tmp stuffe$ ls -l
total 297984
-rw-r--r--  1 stuffe  staff  50855936  3 May 09:32 new.iso
-rwxr-xr-x@ 1 stuffe  staff  50855936  3 May 09:30 ocz_tools_316.iso
-rw-r--r--  1 stuffe  staff  26214400  3 May 09:32 xaa
-rw-r--r--  1 stuffe  staff  24641536  3 May 09:32 xab
StuffeMac:tmp stuffe$ cksum *.iso
1518140433 50855936 new.iso
1518140433 50855936 ocz_tools_316.iso

If you only have a single layer DVD writer (or single layer discs) then changing the command to suit the capacity of your media is advisable, the -b 25m bit will need to be changed to something like -b 4600m for approx 4.6Gb chunks. Don't try to squeeze every last byte from the first DVD, just in case it is rounding up the capacity, I'd probably advice 3500Mb for you to ensure it will fit as either way it's a 2 disc job.

Should you choose a split size that results in more than 2 files being created, they will be called xaa, xab, xac, xad etc in alphabetical order, and the command to stitch them back together remains unchanged. You'll note that the last file is just the remainder, and will typically be smaller unless the split is a direct multiple of the original file - see the following output with a 10Mb split:

-rw-r--r--  1 stuffe  staff   8912896  3 May 10:12 xae
-rw-r--r--  1 stuffe  staff  10485760  3 May 10:12 xad
-rw-r--r--  1 stuffe  staff  10485760  3 May 10:12 xac
-rw-r--r--  1 stuffe  staff  10485760  3 May 10:12 xab
-rw-r--r--  1 stuffe  staff  10485760  3 May 10:12 xaa

Renaming them to be installer_part1 etc might be advisable if you wish to store them for longer than a short time just to transfer them, but ensure you do not change the order of the files when you stitch them back together via a typo etc.

Note that in my example I used an ISO file, purely because it's what I had laying around on my desktop. You should be able to split your installer file just fine as it is without having to change it, but note that this command works on single files only, and as such you cannot use it on a directory/folder, although you can use it on a zipped directory/folder. If you are in any doubt as to your source file, you can simply compress the file regardless to save doubt, simply right click on your file and click the compress option to get a zip file out of it.

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use a double layer DVD disc (8.5GB - 9.4GB), instead of a single layer (4.3GB) disc

such as those found here, I've used these on my iMac with no issues, however older Macs might not have support for dual layer discs.

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