Download Mac OS X Yosemite 10.10.3 latest free latest standalone offline bootable DMG image.
Eg: sudo dd if=Converted-windows.dmg of=/dev/disk2 bs=1m. Sudo dd if=converted.dmg of=USB disk location bs=1m. Follow the below command to copy files and make it bootable. Copy and Create bootable USB from ISO file Mac (now from.DMG) Now copy all the contents in the DMG file to the Pendrive.
Use the Restore Disk Image to Drive dialog box to browse for the DMG file with the installation files for Mac OS X Yosemite in this case, and click the OK button to create a bootable USB of the operating system.
Since you will need to erase all of the files on the USB drive, make sure to back up its contents first. The USB drive must be at least 6 GB in size.
This tutorial is going to show you how to create or restore Mac OS X dmg file into a USB flash disk.