Summary
How to make a bootable USB drive on Linux Mint (19.3) to allow you to install Mac OS X El Capitan on a MacBook with broken or corrupted recovery mode.
This should work if you had downloaded El Capitan previously on your Mac. Alternatively you could download El C on your friends Mac. Don't install as you want to do a clean install. Once downloaded move the Install Mac OS X El Capitan.app to your Mac, and then create a new bootable USB, Create a bootable installer for macOS - Apple Support. Download and keep a copy of the ‘Install OS X El Capitan’ App. (Download from App store but make a copy of it before you install it as the Apple Installer deletes it after you use it.) Put it in your ‘Applications’ folder. Format your blank USB (8GB is a good size) as Apple OS X.
Background
Aug 19, 2021 Download El Capitan OS X is also significant since it’s the last version of Apple Mac OS X releases as its successor Sierra was released in the year 2016 under the brand macOS. El Capitan is a rock formation found in Yosemite National Park, which gives out the meaning that the new release is a solid version of its predecessor, Yosemite. The OS X 10.11 El Capitan installer from the Mac App Store in your Applications folder. The installer will delete itself when you install the operating system, but it can be re-downloaded if.
I was recently given a 2011 MacBook Pro that had been “well-loved” and was therefore a mess of missing applications, ghost files and generally slow-as-hell. Since there wasn’t much worth saving I wiped it and initiated recovery mode in order to re-install OS X (El Capitan).
Having recently fixed a busted MacBook Air I had learned a bit about Recovery Mode (hold Command+R whilst pushing the Power button and release a few seconds after the machine wakes up). I tried that with this machine, and upon hitting “Reinstall MacOS X” was greeted with a prompt telling me it would take -2,148,456,222 days and 8 hours (an uncaught buffer overflow, me thinks). After about 30 seconds, a window pops up saying “Can’t download the additional components needed to install Mac OS X” and the installation gives up. The detailed error log says “Chunk validation failed, retrying” about 1000 times and eventually gives up altogether.
Further investigation suggests this may be something to do with security certificates having expired and hence the machine not being able to download the necessary files from Apple’s servers, but it seems the error can appear for all sorts of reasons. I also tried Internet Recovery (Command+Option+R) but that gave exactly the same error (and would also only have installed OS X Mountain Lion).
I then turned to attempting to make a bootable USB stick of OS X El Capitan from an image downloaded from Apple. I use Linux Mint on my main laptop and that was all I had available. Apple seem to assume everybody has a spare MacBook from which to create a bootable USB so they provide absolutely no documentation to help with this. I also couldn’t find a single guide online that worked from start to finish, so here I summarise what needs to be done.
Steps
As usual, this is all at your own risk 🙂
First you need to go to Apple’s OS Download Page and (step 4) get ahold of “InstallMacOSX.dmg” for El-Capitan. It’s a 6GB file so it might take a ‘lil while. You will also need to find a USB drive with at least 8GB capacity, and make sure it’s blank. The format doesn’t matter, because this procedure will format it correctly.
(In total you will need to use about 15-18GB of disk space by the time you’ve done all the extracting necessary, which shouldn’t be a problem for most computers but it was a challenge for my laptop with it’s 128GB SSD and dual boot Windows/Linux!)
Then you need to get a program called ‘dmg2img’
You can then extract the DMG
Now double click the .img file to mount it. In there is a InstallMaxOSX.pkg file. This requires a utility called “xar” to extract, which can be installed with these instructions (from https://www.oueta.com/linux/extract-pkg-and-mpkg-files-with-xar-on-linux/)
Then build and install with
Now you can extract the .pkg file. It will extract to the current working directory
Now, within the extracted files you will find something called InstallESD.dmg. This actually contains all the interesting boot files, but it isn’t a pristine image, so we can’t just burn it to a USB. Thankfully, a script exists to convert this DMG to a bootable usb, and it’s available here. It takes the DMG and writes everything directly to the USB in the right place.
ONE CAVEAT: When I ran this script on my InstallESD.dmg, it crashed because it didn’t recognise the checksum. I think this is because Apple updates the dmg’s anytime there is a security update for El Capitan so the checksum list isn’t updated. All I did was delete the checksum check from the script above. Essentially, just open the script and delete this section
Once I had done this, I ran the script with my USB connected (/dev/sdb for me, but CHECK YOURSELF with fdisk or similar) and after quite a while it finished copying.
I plugged the USB into the MacBook, and opened the startup menu by holding down Option whilst pushing the power button. This gave me the choice of booting from EFI, or choosing a WiFi network. Click on the EFI, and then follow the prompts to install OS X from the USB drive!
When you’re done, you may need to use Parted or a similar utility to re-format your USB as a normal drive again.
These advanced steps are primarily for system administrators and others who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install on multiple computers without downloading the installer each time.
What you need to create a bootable installer
- A USB flash drive or other secondary volume formatted as Mac OS Extended, with at least 14 GB of available storage
- A downloaded installer for macOS Big Sur, Catalina, Mojave, High Sierra or El Capitan
Download macOS
- Download: macOS Big Sur, macOS Catalina, macOS Mojave or macOS High Sierra
These will be downloaded to your Applications folder as an app named Install macOS [version name]. If the installer opens after downloading, quit it without continuing installation. To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software-update server. - Download: OS X El Capitan
This will be downloaded as a disk image named InstallMacOSX.dmg. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It will install an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.
Use the 'createinstallmedia' command in Terminal
- Connect the USB flash drive or other volume that you're using for the bootable installer.
- Open Terminal, which is in the Utilities folder of your Applications folder.
- Type or paste one of the following commands in Terminal. These assume that the installer is in your Applications folder and MyVolume is the name of the USB flash drive or other volume you're using. If it has a different name, replace
MyVolumein these commands with the name of your volume.
Big Sur:*
Catalina:*
Mojave:*
High Sierra:*
Mac Os X El Capitan Installer Usb
El Capitan:
* If your Mac is using macOS Sierra or earlier, include the --applicationpath argument and installer path, similar to the way this is done in the command for El Capitan.
After typing the command:
- Press Return to enter the command.
- When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
- When prompted, type
Yto confirm that you want to erase the volume, then press Return. Terminal shows the progress as the volume is erased. - After the volume has been erased, you may see an alert stating that Terminal would like to access files on a removable volume. Click OK to allow the copy to proceed.
- When Terminal says that it's been completed, the volume will have the same name as the installer you downloaded, such as Install macOS Big Sur. You can now quit Terminal and eject the volume.
Use the bootable installer
Os X El Capitan 10.11.6
Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:
Apple silicon
- Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing.
- Turn on your Mac and continue to hold the power button until you see the startup options window, which shows your bootable volumes.
- Select the volume containing the bootable installer, then click Continue.
- When the macOS installer opens, follow the onscreen instructions.
Intel processor
- Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing.
- Press and hold the Option (Alt) ⌥ key immediately after turning on or restarting your Mac.
- Release the Option key when you see a dark screen showing your bootable volumes.
- Select the volume containing the bootable installer. Then click the up arrow or press Return.
If you can't start up from the bootable installer, make sure the External Boot setting in Startup Security Utility is set to allow booting from external media. - Choose your language, if prompted.
- Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.
Learn more
A bootable installer doesn't download macOS from the internet, but it does require an internet connection to get firmware and other information specific to the Mac model.
For information about the createinstallmedia command and the arguments you can use with it, make sure the macOS installer is in your Applications folder, then enter the appropriate path in Terminal: