From the forums: Create a boot disk from the OS X installer

InstallMavericksIconXStarting with Lion, OS X has been distributed almost exclusively online through the App Store, or if you need to wipe your system and reinstall, then the installer can be accessed through Recovery Mode.

While these approaches should work just fine, sometimes it might be impractical, such as when you need to install to more than a couple of systems. In these situations, each system will need to download the installation files, which can take a very long time, especially if your bandwidth is somewhat limited. 

At other times, downloading to multiple machines may be an added expense by pushing you over your ISP’s bandwidth limit, which may result in extra fees, or in slowed internet access.

To avoid this, it may help to keep the OS X installation files that are downloaded from Apple, and then apply them to any system that you plan on updating. There are several ways of doing this in OS X, depending on whether or not you get the installers from the App Store, or if you use the Recovery mode in OS X.

The latest version of OS X is available on the App Store for free, and as MacIssues reader “gudac” explains on the new MacIssues forums, when you purchase OS X from the App Store, you can stop the installer from proceeding and then access the application “Install OS X Mavericks” that should be in your Applications folder.

OS X installers

Downloaded OS X installers will be located in your Applications folder.

At this point, you have three options:

  1. Rename the installerAs “gudac” suggests, you can simply rename the saved installer application. Since the App Store and other services recognize purchased programs by name, by just renaming it you should be able to keep it around without it being interfered with.
  2. Copy the program elsewhereKeeping the program in your Applications folder will take up hard drive space, so one option you have is to simply copy the program to an external disk such as a thumb drive. From here, you can attach and run it on any supported Mac to install OS X.
  3. Extract the InstallESD.dmg image
    Disk Utility showing OS X installers

    Be sure the mounted volume in the disk image is the one in the Source field, as opposed to the image itself.

    The installer downloaded from the App Store contains a file called “InstallESD.dmg,” which is a boot image that holds the OS X installation files. This file can be found by right-clicking the installer program and choosing “Show Package Contents,” and then going to the Contents > SharedSupport directory.

    If you do not have access to the App Store to download the OS X installer, you can also get this image file by using the OS X Recovery Mode. To do this, get an external drive that is at least 8GB, and then boot to recovery mode by holding Command-R at startup. Now choose the option to install OS X, and select your external drive as the destination. Proceed and watch the download, and when the system restarts, unplug the drive.

    You can now plug this drive into any Mac, and you should see a folder called “Install Data” containing the “InstallESD.dmg” file.

    Once you have the disk image, you can use Disk Utility to restore the image to a DVD or hard disk. Simply double-click the image to mount it, and then open Disk Utility. Then select the mounted volume (called “Mac OS X Install ESD”, under the InstallESD.dmg file in the sidebar) click the Restore tab that appears. In the panel that shows up, the Source field should have the selected disk, with an empty Destination field. Now drag the attached external drive volume to the Destination field, and click the Restore button. This will erase the disk, and copy the contents of the image to it.

    You can now boot to this disk from any Mac by holding the Option key at startup, and then attaching and selecting the disk, and choosing it when it appears in the boot menu.

With these options, you can perform a single download for OS X, and then optionally create an installation drive, and then apply it to any Mac you have that is supported.

Have a tip or suggestion for how to use your Mac? Post it in the MacIssues forums.

6 thoughts on “From the forums: Create a boot disk from the OS X installer

  1. darkdreamer4u

    Ok, now, could this OSXinstaller be copied onto a thumb drive instead of an external drive or DVD?
    And could we install a utility like TechToolPro as well and thus, make ourselves a nice emergency tool?

    1. Topher Kessler Post author

      Yes, provided it is large enough to accommodate the data. An 8GB drive should be plenty. I should have been clearer in stating that USB flash drives are equivalent in most functions to external hard drives, and in this situation they can be treated the same.

  2. MaX

    It is also a good idea to save the Mac OS X installer from the Applications folder (before installing, since after that it gets deleted) on a booting USB PenDrive in case it is required to install again.

  3. Scott Harris

    I do Mac desktop support for individuals and small businesses. Many of them have very slow Internet connections because they live in remote areas, or depend on Internet by a cell connection where they pay for the amount of data they use. I use the methods mentioned above with OS X installs and updates and save myself and my clients much time and money. Is there a similar method to “capture” installers for other Apple products (Pages, Numbers, Keynote, Garage Band, iMovie, iTunes, and iPhoto/Photos. Apple’s new model of software distribution works in a world where bandwidth is fast and cheap but many of my clients don’t live in that world.

    Thanks for your great tips and info.

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