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I am aware of how to make a bootable USB from the downloaded Install.app of El Capitan.

Apple have now released an update to El Capitan: OS X 10.11.1.

Is it possible to apply this minor update to the same bootable drive so I do not have to install the update after clean installing El Capitan from the drive?

If I need to do a clean install of several Macs, I'd rather not manually install the 10.11.1 update each time as well.

I obtained the update DMG file from Apple: https://support.apple.com/kb/DL1845

When you open the DMG file, it mounts the volume which simply contains a PKG file to install the minor update.

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    Since modifying the os x installer is very complicated and honestly I don't know how. You can backup a clean install of OS X with the update you want using, for example, disk drill, this will allow to convert the entire OS X disk to a dmg file. Then you can easily make your bootable usb installer from this dmg. cleverfiles.com/hard-drive-backup.html
    – enzo
    Oct 27, 2015 at 11:37

1 Answer 1

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The probably easiest solution is to simply download the latest OS X El Capitan installer after a minor update was released. Usually the newest installer available in the App Store already includes the update.

To get the build version of the OS installed by the OS X installer.app enter in Terminal.app:

cat /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Info.plist | grep -A 1 BuildMachineOSBuild

The output

  • 15A... usually indicates a 10.11.0 build
  • 15B... usually indicates a 10.11.1 build
  • 15C... usually indicates a 10.11.2 build

and so on. The build version here is not identical with the build version of the later installed operating system. To get that one you have to mount the InstallESD.dmg in "/Applications/Install OS X El Capitan.app/Contents/SharedSupport/". Then cd to "/Volumes/OS X Install ESD" and enter "open BaseSystem.dmg".

To get the Build or System version then enter:

cat /Volumes/OS\ X\ Base\ System/System/Library/CoreServices/SystemVersion.plist | grep -A 1 ProductBuildVersion

or 

cat /Volumes/OS\ X\ Base\ System/System/Library/CoreServices/SystemVersion.plist | grep -A 1 ProductVersion

With the new OS X installer you can create a new bootable USB.

Depending on your internet connection that's probably faster and less hassle/error-prone than merging an update in an older full installer.

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  • How to confirm OS build version number from within the .app file contents?
    – Trung Nguyen
    Oct 27, 2015 at 12:15
  • @TrungNguyen added how to get the build version
    – klanomath
    Oct 27, 2015 at 12:29
  • After mounting the installer, I found it here: /Volumes/Install OS X El Capitan/System/Library/CoreServices/SystemVersion.plist
    – Trung Nguyen
    Oct 27, 2015 at 12:45
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    Re-downloaded the Installer App from AppStore purchases and confirmed that the build number matches 10.11.1. Indeed a much simpler method!
    – Trung Nguyen
    Oct 27, 2015 at 12:47
  • See also OSInstall.mpkg/Distribution
    – youfu
    Mar 12, 2017 at 5:07

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