Make El Capitan Usb Installer

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.

Create Bootable USB for Mac OS X El Capitan with TransMac. A new pop up box will appear, click on the three-dots, and then select the macOS X El Capitan.DMG file from Windows. Then click on OK. Choose Mac OSX El Capitan DMG file. Since the file is huge so it will take quite time to complete. It may take about 20 to 30 mins or more.

Background

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

One way is to use DiskMakerX to create a bootable USB drive with a downloaded install image of the OSX loaded on it. This method requires 1) a functioning second Mac for running DiskMakerX and 2) a USB drive with at least 12 GB available. The method is summarized in a comment in this Apple Community discussion thread. Make sure that the installer that downloads the El Capitan file is located in the /Applications folder under the name ‘Install OS X El Capitan.app‘. Step 2: Next, we’re going to need to format the USB flash drive to get it into a state where it can accept the payload for the installation of El Capitan. Jan 14, 2021 Creating bootable USB Installer can be done in different ways specifically create bootable USB Installer for macOS X El Capitan on Windows and other macOS versions. The first way to do manually and the second way is to do a software that is pre-build to do all those with a click or two.

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.

When Apple introduced Yosemite, it changed the way it distributes operating systems for the Mac. Now, you can’t buy a copy of the Mac OS installer. That’s a problem if you have a limited broadband connection or metered broadband connection. You’ll need to create a portable offline installer in these situations.

Download or Purchase the Mac Operating System

The first step is to go to the App Store and search for the current operating system. Currently, that’s El Capitan. If it’s already installed on your Mac, the App store will warn you the operating system is already on your system. If it isn’t already installed or you didn’t purchase it on your current Mac, under El Capitan it will say

Internet too slow? Check out some tools to test your connection.

If you’d like to create an installer for an earlier operating system you purchased, you can still do that from the App Store. Go to the

The Easy Way: DiskMaker X

DiskMaker X is a free program that does the hard work of creating the USB installer. They do take donations, so if it’s helpful to you, you might throw some money in the tip jar.

After your open the program, it finds the operating system installers on your Mac. In this example, I’ll create an El Capitan installer. Next you’ll need an 8 GB or larger disk. This media can be a USB stick, but I use an SD card. Since most Macs that run Yosemite have an SD card slot, I think it’s easier.

DiskMaker confirms the disk you want to use for the installer. Then it warns you it needs to erase that disk. Confirm again you have the right disk and then click continue. After authenticating your Mac’s administrator name and password, a few minutes later you’ll have a complete installer.

The Hard Way: Terminal Commands

If you’re more comfortable with terminal than using a third-party program, it is possible to create the installer. You’ll need a disk formatted

Don’t fear terminal: There some cool tricks you can do it in or just be more productive.sudo /Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia –volume /Volumes/ElCapinstall –applicationpath /Applications/Install OS X El Capitan.app –nointeraction

After you put in the password, the media creation process begins.

Why Do You Need This?

If you can download it again, why waste a flash drive or an SD card? Ideally, your Mac has a recovery partition you can boot off of to repair problems. Sometimes that partition isn’t there. An offline installer includes disk utility so you can solve problems.

The most common reason though is if your Mac’s hard drive fails. If you only have one Mac, you won’t have an easy way to reinstall the operating system. Creating the installer in advance solves the problem.

This is true for Windows too:
It’s handy to have a system repair/recovery disk for Windows 7, Windows 8, or Windows 10

Finally, if you want to reinstall your OS to troubleshoot problems, waiting for the installer takes a long time. When things don’t work, you probably wait for a download. If you’re on a slow connection, the download could take several hours.

Overall for the cost of one small USB flash drive or SD card, you can have the peace of mind that you can solve your Mac problems instantly.

ALSO SEE:5 Free Portable Antivirus Software for Windows to Fix PCs On the Go

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