How To Create An External Installation Device

Creating An External Installation Device

• For Mac OS X 10.4, 10.5 or 10.6
• For OS X 10.7 and 10.8
• For OS X 10.7 and 10.8 (Using Apple's "Recovery Disk Assistant")
• For OS X 10.9 or later

For Mac OS X 10.4, 10.5 or 10.6

1. To be safe:
• Restart your computer.
• Quit all running applications.
• Disconnect all external devices except for monitor, keyboard, mouse and required storage volumes.
• Eject all optical discs.
• Unmount all servers.
2. Connect your external device e.g. hard disk.
3. Format/partition your external device.
NOTE: For safety the volume/partition you are going to use must be at least 10GB in size. However, the volume/partition you are going to use cannot be used for anything else so there is no need for it to be too large. With large hard disks we highly recommend partitioning them before using them as an external installation device. There is nothing stopping you creating multiple partitions and putting different versions of the Mac OS X installer on each partition.
4. Insert your original "retail" Mac OS X installation DVD disc or the install disc for your particular computer.
5. Copy the volume name of your original "retail" Mac OS X installation DVD disc exactly (usually "Mac OS X Install DVD") to the external device volume you are going to use.
6. Go to Macintosh HD > Applications > Utilities > Disk Utility.

7. On the left select your original "retail" Mac OS X installation DVD disc titled "Mac OS X Install DVD".
NOTE: with macOS 10.13 or later Disk Utility only shows volumes by default and the Sidebar can be hidden - go to View menu > Show Sidebar and View menu > Show All Devices to see everything.
8. On the right click the "Restore" tab.
9. Drag the "Mac OS X Install DVD" icon of your install disc from the left to "Source".
10. Drag the "Mac OS X Install DVD" icon of your external device from the left to "Destination".
11. As you've erased/formatted your external device in the steps above you do not need "Erase Destination" ticked but it does no harm to leave it.
12. Click the Restore button.
13. For safety don't do anything else on your computer until the process has finished.
14. When the process has finished Quit Disk Utility.
15. Eject the Mac OS X installation DVD disc.
16. Unmount and disconnect your external device.
17. Your External Installation Device is now ready for use.
18. To boot from it shut down your target computer, connect your external device and startup your computer holding down Option to choose the external installation device from the Startup Manager.
19. Install Mac OS X as required.

For OS X 10.7 and 10.8

1. To be safe:
• Restart your computer.
• Quit all running applications.
• Disconnect all external devices except for monitor, keyboard, mouse and required storage volumes.
• Eject all optical discs.
• Unmount all servers.
2. Connect your external device e.g. hard disk.
3. Format/partition your external device.
NOTE: For safety the volume/partition you are going to use must be at least 10GB in size. However, the volume/partition you are going to use cannot be used for anything else so there is no need for it to be too large. With large hard disks we highly recommend partitioning them before using them as an external installation device. There is nothing stopping you creating multiple partitions and putting different versions of the Mac OS X installer on each partition.
4. If you have an Install DVD (or the official Lion thumb drive):
1. Insert your Install DVD (or the official Lion thumb drive).
2. Copy the volume name of the Install DVD (or the official Lion thumb drive) exactly (usually "Mac OS X Install ESD") to the external device volume you are going to use.
3. Go to Macintosh HD > Applications > Utilities > Disk Utility.

4. On the left select the Install DVD (or the official Lion thumb drive) titled "Mac OS X Install ESD".
NOTE: with macOS 10.13 or later Disk Utility only shows volumes by default and the Sidebar can be hidden - go to View menu > Show Sidebar and View menu > Show All Devices to see everything.
5. On the right click the "Restore" tab.
6. Drag the "Mac OS X Install ESD" icon of your install disc/USB thumb drive from the left to "Source".
7. Drag the "Mac OS X Install ESD" icon of your external device from the left to "Destination".
5. If you have an OS X install disc image:
1. Copy the OS X install disc image (usually "InstallESD.dmg") to your local hard disk e.g. the Desktop.
2. Double click the disc image (usually "InstallESD.dmg") to open it.
3. Copy the volume name of the mounted disc image exactly (usually "Mac OS X Install ESD") to the external device volume you are going to use.
4. Go to Macintosh HD > Applications > Utilities > Disk Utility.

5. On the left select the mounted disc image titled "Mac OS X Install ESD".
6. On the right click the "Restore" tab.
7. Drag the "Mac OS X Install ESD" icon of your mounted disc image from the left to "Source".
8. Drag the "Mac OS X Install ESD" icon of your external device from the left to "Destination".
6. As you've erased/formatted your external device in the steps above you do not need "Erase Destination" ticked but it does no harm to leave it.
7. Click the Restore button.
8. For safety don't do anything else on your computer until the process has finished.
9. When the process has finished Quit Disk Utility.
10. Eject the "Mac OS X installation ESD" icon (of the Install DVD/thumb drive/mounted disc image).
11. Unmount and disconnect your external device.
12. Your External Installation Device is now ready for use.
13. To boot from it shut down your target computer, connect your external device and startup your computer holding down Option to choose the external installation device from the Startup Manager.
14. Install Mac OS X as required.

For OS X 10.7 and 10.8 (Using Apple's "Recovery Disk Assistant")

1. Download Apple's Recovery Disk Assistant and copy the application to your boot disk "Applications" folder.
2. To be safe:
• Restart your computer.
• Quit all running applications.
• Disconnect all external devices except for monitor, keyboard, mouse and required storage volumes.
• Eject all optical discs.
• Unmount all servers.
3. Connect your external USB device.
4. Open/double click the "Recovery Disk Assistant" in your Applications folder
5. Follow the on screen instructions.
6. When the Recovery Disk Assistant completes, the new partition will not be visible in the Finder or Disk Utility (see this Apple Tech Article).

For OS X 10.9 or later (Using Apple's "createinstallmedia")

1. To be safe:
• Restart your computer.
• Quit all running applications.
• Disconnect all external devices except for monitor, keyboard, mouse and required storage volumes.
• Eject all optical discs.
• Unmount all servers.
2. Connect your external device e.g. hard disk.
3. Format/partition your external device.
NOTE: For safety the volume/partition you are going to use must be at least 10GB in size. However, the volume/partition you are going to use cannot be used for anything else so there is no need for it to be too large. With large hard disks we highly recommend partitioning them before using them as an external installation device. There is nothing stopping you creating multiple partitions and putting different versions of the Mac OS X installer on each partition.
4. Go to Apple's support site where you will find official instructions on making a bootable installer

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