Uploading a disk image may in some cases be quite troublesome, e.g. uploading to .Mac simply because you can’t resume the upload if it fails. A way around would be to upload in segments.

There are number of tools that can split your image (DMG, CDR, etc.) into pieces. Some of them work, some don’t but the most bulletproof way is to do it in the Terminal (Applications > Utilities > Terminal).

There’s a tool on a Mac that does pretty much everything concerning the disks. It’s called hdiutil. It can attach, detach (eject), verify, mount, unmount and segment a volume to name a few. To use this tool you have just got to type in a command. For a start you may want to get a view on hdiutil’s features by typing hdiutil help. Hit Enter to execute a command.

To segment an image, let’s say DMG you could use a command:

hdiutil segment -o mydvd -segmentSize 100M /Users/[your Mac username]/Desktop/dvdimage.dmg

That command would create segments (mydvd.002.dmgpart, mydvd.003.dmgpart, etc.) in your Home folder of an image named dvdimage.dmg on your desktop.

‘-o mydvd’ stands for the prefix that is used to name the segments. Segment size would be 100MB as defined by the segmentSize parameter. If you’d want the segment size to be 500KB you could just use 500k instead of 100M. Alternatively you could also split your image by the number of segments. In that case you should replace ‘-segmentSize 100M’ with ‘-segmentCount 5′ for example. That would split your image into 5 segments.

A good thing about it is that you don’t even have to rejoin these segments later. You can just click the first segment (in above example it would be mydvd.dmg) so Mac will verify the image and attach the DMG as it usually does. Or use Disk Utility (Applications > Utilities > Disk Utility) to burn it by using the first segment as well.