Starting 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.
At this point, you have three options:
- 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.
- 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.
- Extract the InstallESD.dmg image
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.
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.
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