In addition, you can easily update a USB stick or external hard drive each time an update to Mac OS X is released, as explained below with a DVD, you have to toss the disc in the trash and start over, which is both a hassle and bad for the environment. More and more Macs ship without a built-in optical drive booting and installing from a DVD is very slow and 8GB flash drives can be found for $10 or less-there’s little reason to opt for a DVD anymore. Though it’s possible to make one, I don’t recommend it these days. When finished, quit out of Disk Utility and now select the “Install Mac OS X” option from the menuġ1.You may have noticed that I didn’t mention making a bootable install DVD. Click the “Erase” button and let the drive format – this is the point of no returnġ0. Select “Disk Utility” and choose the hard drive you wish to format, click the “Erase” tab, and then pull down the “Format” menu and select “Mac OS Extended (Journaled)” as the type, name the drive if you wishĩ. Choose the “Mac OS X Installer” startup volume from the boot menuĨ. With the boot installer drive connected to the Mac, reboot and hold down the Option keyħ. Confirm you would like to do this, and when complete you should have a fully bootable Mountain Lion installation drive.Ħ. Drag your destination drive (the desired USB or FireWire drive volume) to the Destination field, and then click the Restore button. When you do this you should see the disk image appear in the Source field, but if not then drag it there.ĥ. Select the InstallESD.dmg file in Disk Utility and click the Restore tab that appears in the main Disk Utility window. Optionally partition it by selecting it and using the Partition tab to split it into two logical volumes (one for the Mountain Lion installer and the other for extra storage space) by clicking the plus button to create a new partition, and then setting the first partition to be 4.8GB in size.Ĥ.

Connect a spare USB or FireWire drive that has at least 6GB of capacity, which should show up in Disk Utility. If you wish to create a USB or FireWire install drive instead, then continue on to step 3.ģ.

In Disk Utility select the InstallESD.dmg file, and then you can click the Burn icon in Disk Utility’s toolbar to burn the image to a DVD (single-layer 4.7GB discs do not have enough space, so use dual-layer 8.5GB discs). Open Disk Utility (in the Applications > Utilities folder) and drag the InstallESD.dmg image to the device sidebar, where it should appear under your various disk and volumes listings.Ģ.

Mac os 10.8 dmg