Mac DMG images are practically unusable in a non-Mac system in that format. They can be converted to ISO images in Ubuntu for easy burning, mounting, or use in a virtual machine.
Once you have the DMG file you want to convert to an ISO file, you need to install dmg2img
sudo apt-get install dmg2img
Now, assuming the DMG file you want to convert is image.dmg, run the following command:
After a few minutes or processing, your DMG will be converted to an IMG file in ISO format (image.img). If you need the ISO extension, simply rename the file:
mv image.img image.iso
Note: IMG files created by Nero are NOT in ISO format and cannot simply be renamed. If you want to convert a Nero IMG file to ISO, use the ubuntu utility nrg2iso, but it’s not required above.