You can use DropDMG to create exact copies of CDs, DVDs, and Blu-ray discs, for
example:
- Your macOS install discs.
- A bootable emergency CD for disk repair software such as
DiskWarrior or Drive
Genius.
- Video discs that you’ve created. (In this case, use the .cdr
format instead of the .dmg format.)
To do this:
- Go to the Configurations tab of DropDMG’s Settings window and
set DropDMG to create a read-only .dmg image.
- Drag the CD or DVD icon onto the DropDMG window or use one of the
other methods. DropDMG; it will create a device image of the disc
and save it as a .dmg file.
- Eject the disc.
- Use the Burn… command to burn the .dmg file, making sure that
Burn contents of disk images is selected.
- DropDMG will ask you to insert a blank disc; after doing so, click
the Burn button.
Tip: DVDs are faster to access than CDs. If you burn a DVD copy of an
emergency boot CD, your Mac will boot approximately 25% faster from the backup
than from the original CD. This can be a savings of a couple minutes.