In an ideal world, sysadmins everywhere would only need to manage one or two operating systems—one desktop, one server—and nothing else. Unfortunately, business operations often dictate a different method than that, leaving it up to IT to bridge the gaps caused by fragmentation between multiple OS, hardware, and software instances. For IT staffers, there's seemingly no end to the number of tools they must carry with them, doubly so if they provide mobile support.
Below is a solution to ease the load by providing access to any versions of OS X in one small, easy-to-carry, bootable flash drive. There are a few requirements I'd like to share with you prior to beginning the tutorial: • Apple computer with OS X 10.9+ • Install DVD media/DMG or installer for each version of OS X to be included • USB flash drive with at least 8 GB for each version of OS X to be supported.
For the purposes of this article, I'll be creating three installers of OS X: 10.8, 10.9, and 10.10. However, the limit is really based on the total capacity of the drive to be used. • Launch Disk Utility.app and partition the external drive as three separate partitions of 8 GB each. I suggest naming each partition with the OS X version that will occupy the space to make it easier to identify later ( Figure A). Figure A • Click the Options button, select the GUID Partition Table, and then click OK and Apply to commit the changes ( Figure B). Figure B With the drive now partitioned properly, see the sections below to go about copying the media/installer contents to the drive. Certain versions of OS X will require a different procedure to complete.
Apple OS X 10.7 (Lion), 10.8 (Mountain Lion) • Right-click the installer and select Show Package Contents from the context menu ( Figure C). This reveals the contents of the installer itself and makes navigating the structure possible. Figure C • Drill-down through the Contents Shared Support directories and drag-drop the InstallESD.dmg to the desktop ( Figure D).
Figure D • Launch Disk Utility and click on the partition to copy the install files to, then click the Restore tab. Next, click the Image button next to Source and point to the InstallESD.dmg file recently copied to the desktop. Next, drag-and-drop the partition created on the USB to the text box next to Destination ( Figure E). Figure E • Once the source and destination fields are selected, click the Restore button. You'll be prompted to confirm that the process will erase the contents of the partition by clicking Erase ( Figure F). Figure F • The process takes about 30 minutes, depending on the speed of the computer.