I have downloaded the El Capitan dmg file (InstallMacOSX.dmg) provided by Apple. The expanded dmg image contains the package "InstallMacOSX.pkg" which should be run to create the El Capitan installer but fails with the following message "This version of OS X 10.11 cannot be installed on this computer." presumably because quite reasonably it would not make sense to install on top of a later version of the OS. However in this case I want to create a boot USB drive for an installation on another Mac.
I am stuck in a chicken and egg situation where I need another machine running El Capitan or earlier to create and El Capitan boot installer.
Best Answer
I have noticed that these instructions no longer work as expected when using the current
InstallMacOSX.dmg
file, which can be downloaded from either the Apple website How to get old versions of macOS or the Apple website How to create a bootable installer for macOS. These instructions may work as expected, if you are using an older saved version of this file. At best, these instructions are just a hack and Apple has every right to change theInstallMacOSX.dmg
file to prevent the desired results.I have posted a new answer to this question.
This new answer is must less of a hack, because Apple explicitly inserted code into the El Capitan installer to bypass the checking of the model when executed in a "VMware Fusion Player" virtual machine. So, Apple evidently intends for users of newer model Intel Macs to use this new answer to retrieve the
Install OS X El Capitan
application. Still, I would like know from Apple why they thought such a complex procedure is necessary.Below is my original answer.
There is a link on the Apple website How to get old versions of macOS that will download a file that can be used to create the
Install OS X El Capitan
application. However, if the model Mac is too new to allow the installation for El Capitan, then message given below will occur when trying to create theInstall OS X El Capitan
application.If you are trying to create a USB installation flash drive of use on another Mac computer, then you can still use the downloaded file to create this installer. The instructions are given below.
This method was verified by using the following configurations.
The following steps can be used to create a USB installer for El Capitan.
Use instructions on the Apple website How to get old versions of macOS to download
InstallMacOSX.dmg
.Use the Disk Utility to erase a 16 GB or larger flash drive. If the Disk Utility window has a
View
pulldown menu, make sureShow All Devices
is selected. Highlight the flash drive, then click on theErase
button. Use the setting shown in the image below.Next, click on the
Erase
button. When finished erasing, click on theDone
button.Use the Finder applicaition to open
InstallMacOSX.dmg
.Enter the commands given below. A folder named
El Capitan
will be created in the/tmp
folder to hold temporary files.After entering the last command given above, you may get a message similar to the one given below.
Some versions of macOS will produce this message while other versions do not. I suspect this is an fatal message because an exit status of 1 was returned.
Therefore, I was able to ignore this error. However, the error can also be avoided by applying the following steps given in the section below titled Alternative to Using the
asr
Command.To finish creating the bootable USB flash drive El Capitan installer, enter the commands given below.
Remove the flash drive. You are done.
Alternative to Using the
asr
CommandThe command given below may generate a error message and/or hang depending on the version of macOS and perhaps the model Mac you are using.
You can avoid entering the above command by following the steps given below.
If the volume on the USB flash drive is no longer labeled
MyVolume
, then use the Disk Utility to erase the flash drive. Highlight the flash drive, then click on theErase
button. Use the setting shown in the image below.Next, click on the
Erase
button. When finished erasing, click on theDone
button.Enter the following command to create a sparse flash drive image.
Basically, you want to restore to volume
MyImage
from the hidden fileBaseSystem.dmg
. The hidden fileBaseSystem.dmg
is shown in the Finder window image shown below. The driveOS X Install ESD
can be found in the hidden volumeVolumes
in the root folder.Highlight the
MyImage
volume shown in the Disk Utility main window. Click on theRestore
button, then theImage
button. Select theBaseSystem.dmg
file, as shown below. Next, click on theRestore
button.After a successful restore, you should see the image shown below. You can click on the
Done
button and quit the Disk Utility.Also, you should get the following popup.
Enter the following commands to clone to the flash drive.
You can now proceed with the rest of the steps.
References
How do I make a bootable USB flash drive on a Mac?
What is the best way to generate a Yosemite or Mavericks Install USB flash drive?
Install El Capitan with VirtualBox on OS X