Making a bootable OSX USB from dmg on Linux

Install dmg2img

sudo apt-get install dmg2img

Convert DMG image file to ISO file

dmg2img -v -i /path/to/image_file.dmg -o /path/to/image_file.iso

Copy ISO image to USB

sudo dd if=/path/to/image_file.iso of=/dev/sdb && sync

sdb is an example. In your case it might be different

Edit

You can do the conversion and actual writing in one pass, if you don't need the .iso afterwards: it will take half the time as converting to .iso and THEN writing to the USB device. Just do:

sudo dmg2img -v -i /path/to/image_file.dmg -o /dev/sdb

Again, sdb is an example. In your case it might be different.

Have you tried "Acetoneiso"?

It'll convert the DMG to an ISO for you. After that, the easiest way I know of to make a bootable USB is using DD.

dd if=/path/to/osx.iso of=/dev/sdX && sync

Note: sdX is an example, you will have to check your flash drive address (usually sdb if you have only one hard disk). Do not add a partition # after that (such as sdb1). This method is a little hard on flash drives (I have killed one or two doing this relatively frequently, but once should be fine).

If you are unfamiliar, DD is a bit by bit copy and sync just verifies that all files have been written to the usb.

Try booting from Internet Recovery (Command + Alt + Shift + R) and opening the installer app from Terminal.

Open Terminal in recovery and:

cd /Volumes/NAME-OF-YOUR-USB-STICK/
cd The-Name-Of-Your-Installer.app/Contents/MacOS
./InstallAssistant

The installer should load.

If you can find another Mac, try the Disk Utility App.

You can "Restore" your 10.8 DMG to your USB drive. This will make your USB drive be bootable.