Multi Mac OS X Rescue Drive

Recently someone posted a great idea in a Facebook group for users of old Macs — but apparently wasn’t interested enough in the community to describe how it was accomplished. The idea is to have an external USB drive with multiple Mac OS installers on it, so you can restore or recover a wide range of Macs. Although all the instructions are online, they’re scattered across different sites that have to be pieced together. Here’s my attempt to collected everything you need to make a multi-OS recovery disk for almost any Mac made in the last 15 years.

Multi-boot Mac OS Recovery USB Drive

Things You’ll Need

  • A working Mac with a relatively modern OS (I used a 2008 MacBook Pro running a patched High Sierra)
  • The install media (disk, disk image or installer app) for each OS revision you’ll want (see links at the bottom)
  • At least 100gb external USB drive (an actual drive — not a USB key)
  • Optional, the DosDude patchers for any Mac OS you may want to shove on an unsupported Mac
  • Optional, but recommended, the latest Combo update for each Mac OS you may be installing. (I’ll include links to download these at the bottom of this post)
  • Moderate proficiency with Apple’s Disk Utility and just a little bit of Terminal comfort

Note: You’ll notice that these instructions stop at Mojave. So do I. You could argue that Catalina’s murder of 32-bit apps was necessary for the ARM-transition — and maybe that was right for Apple, but you can read why I don’t think its great for consumers.

Prepping the Drive

Warning: Throughout this process you’ll be completely wiping and over-writing drives and partitions. Always double check your target before confirming any action — you don’t want to accidentally wipe out the wrong volume. If you can, disconnect any drives you won’t need.

  • Launch Apple’s Disk Utility and select your USB drive on the left.
  • Using the toolbar at the top, format the entire drive (not just a partition) choosing the GUID partition scheme. Just use the default Format — usually Mac OS Extended (Journaled) — since we’ll be over-writing it later.
  • You should now have a big, empty USB drive with a single partition.
  • Using the toolbar at the top, click the Partition button, and add 4 partitions. For Disk-based installs, 7GB will work. For App-based installs, you’ll want 20GB partitions. Again, the default Format is fine. At this point, it may be tempting to add more — you can, but I found that Disk Utility is dumb if you add too many at once. You can add more later, but note that the total number of bootable partitions is 9.
  • Hit Apply and wait while the partitions are configured. When done, you should have 4 partitions you made, and a 5th partition of the remaining space. You can revisit this step when you want to add more than 4 operating systems, but I recommend you leave yourself a spare partition for OS Updates and other App installers you may need when rescuing a Mac.
It took multiple trips to the Partition window to get this many created successfully!

Writing the Bootable Partitions

There are three different techniques you’ll need to follow, depending on the era of the Mac OS, and whether you want to Patch it. I’ll cover each in brief, but depending on path, you may want to read up on other sources about the particular OS or Patch you care about — I’ll include links where I have them:

Writing Disk-based Installs

  • Early OS X used a 4-CD install approach and aren’t included in this tutorial. I’m still working on a disk emulator solution for this.
  • Starting in OS X Tiger, there was a DVD-based installer, but I haven’t been able to find a bootable image, and all my attempts at making this have failed.
  • I skipped Leopard, since it was a bit of a stinker. Everything that runs Leopard also runs Snow Leopard — and since it was my favorite OS X release, I started there.

Using either a bootable Mac OS X DVD, or a good disk image of the DVD:

  1. Pick a partition on your USB drive to host the new install and change the drive label like “Snow Leopard” or “Mountain Lion” (this isn’t strictly necessary if you’re doing this first, since it will be over-written, but the practice becomes important as you go along so you don’t over-write the wrong partition!)
  2. In Disk Utility, select the partition you picked, and press the Restore button in the toolbar at the top.
  3. Disk Utility will ask for the restore source — choose the Mac OS X DVD, or if using an image, click the “Image” button and find your Mac OS X disk image.
  4. Wait while the image is written to the partition.
“Restore” an Installer Disk Image to a Partition

The process is the same for Snow Leopard, Lion, Mountain Lion and Mavericks. And its really that easy — you might want to customize the partition’s boot entry a little, but I’ll cover that later.

Writing Un-Patched App-Based Installs

  • Yosemite seemed to be an awkward transition between disk-based and app-based installs; the only distribution I could find was an Install package, which didn’t work for any method. I had to skip this release.
  • El Capitan was the first true app-based deployment, and Apple actually documents how to write it to a USB volume — as they did with every subsequent release. We’ll be leaning on their help for non-patched partitions.

With the macOS Installer app handy in your Applications folder:

  1. Choose the partition you want to write, and give it a good drive label in the Finder, like “ElCapitan” — it’ll be easier if you leave spaces out, since we’ll be typing it in the Terminal.
  2. Launch Terminal
  3. Enter the command Apple specifies for the OS you’re writing, substituting your drive label for MyVolume value. Since I used “ElCapitan” in my example, the command will look like this — but remember this is different for each release. I’ll included a cheat sheet below.
    sudo /Applications/Install\ OS\ X\ El\ --volume /Volumes/ElCapitan --applicationpath /Applications/Install\ OS\ X\ El\
  4. Wait while the image is written.

That’s it — but now you’re really going to want to customize the boot entry, so read on.

Writing Patched App-Based Installs

  • Starting with macOS Sierra, Apple really started tightening the screws on killing off older Macs with (sometimes artificial) hardware restrictions. Fortunately, a legend named DosDude1 has work-arounds — although be aware there are some caveats where older hardware may actually been unsupported, or have issues. Check his compatibility info for each release.
  • There is no harm in running a patched install on a machine that doesn’t need patches — you can skip patching post-install if you don’t need them. There’s no reason to have patched and unpatched install partitions.

With the macOS Installer app handy in your Applications folder, and the related DosDude patch available on the same computer:

  1. Choose the partition you want to write, and give it a good drive label in the Finder, like “High Sierra”
  2. Launch the DosDude patcher
  3. Click the first big icon to find the macOS Installer
  4. Click the second icon to choose the partition you just picked
  5. Click “Start Operation…”
  6. Wait while the image is written.
DosDude1 not only patches, but also writes the bootable partition. Genius!

If it fails, check your partition (re-format just the partition if necessary), and your macOS Installer app and try again — sometimes it can be a little touchy.

That’s it. You probably won’t need to customize the new partition’s boot entry, since the later OSes did a good job of this, but if you want to, read on.

Customizing Each Partition’s Boot Entry

  • For some versions of Mac OS, you might want to change the icon that shows up in the Finder for each partition. In most cases, double click on the Volume in the Finder and you’ll find an Installer or Folder that has a nice looking icon. Click on the Icon and choose “Get Info” from the File menu (or press Command+i). In the Info window, click on the icon (top left) and choose “Copy” from the Edit menu (or press Command+c). Now click on the Volume icon and “Get Info” on that, click on its icon and choose “Paste” for the Edit menu (or press Command+v).
  • The drive label you picked for your paritions will get over-written during the imaging process, and you’re free to rename it in the Finder — but that value gets ignored by the Mac’s boot loader. Some of them are really generic, like “OS X Installer”, which doesn’t really help. For older installers, where you need it most, a simple Terminal command will fix it. Launch Terminal and enter a command like:

    sudo bless --folder /Volumes/ -label

    Subsitute with the partition name and with the name you want to see in the Mac boot loader. For example:

    sudo bless --folder "/Volumes/Mac OS X Lion Install ESD" -label "Lion Install"
  • Note: If you want to customize newer Installs, there’s an extra step, which is documented here.

Using your USB Multi-OS Installer

Macs have a built-in boot loader that will enumerate available bootable media (including partitions) automatically. You don’t need to do anything fancy with an EFI partition. To use:

  1. Turn off the target Mac
  2. Plug in your new USB Drive
  3. Hold the Option key on the keyboard
  4. While still holding Option, turn on the Mac
  5. Continue to hold Option until you see icons start to appear for the different boot possibilities
  6. Select the one that is appropriate for the Mac you’re trying to rescue and boot from it

Some very old Macs may not be able to handle the partitions on your drives — those old Macs probably can’t use any of the Operating Systems on your drive anyway.

Additional Ideas

  • You can have up to 9 bootable partitions on your USB drive, so you can return to the Partitioning instructions and continue to add new partitions inside the remaining space.
  • Even if you max out the 9 bootable limit, you’re likely to be left with one big partition that isn’t bootable. I use this partition to keep Combo Update installers, and app installers that I frequently use on rescue Macs.

Finding the Bits

As of this writing, the bits for all the recent OS X or macOS releases can still be found online — some even from official sources. I recommend you download everything you think you might need and archive it somewhere for the day they disappear…

Mac OS X 10.4 Tiger
Mac OS X 10.6 Snow Leopard
Mac OS X Lion 10.7
Mac OS X Mountain Lion 10.8
Mac OS X Mavericks 10.9
Mac OS X Yosemite
Mac OS X El Capitan 10.11
macOS Sierra 10.12
macOS High Sierra 10.13
macOS Mojave 10.14

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