If you are interested in knowing how to create a bootable external SSD and do not care for the background, a list of steps is at the bottom of this post.

Background

Last year, I bought Apple’s M1 chip Mac Mini. Previous to that, I was using a mid-2011 iMac that I had since, well, 2011. The iMac’s mechanical HDD just became slow to the point where booting up and logging in would take 5-10 minutes for everything to fully load. I enjoy MacOS, though. I’ve used Windows before, but I just don’t enjoy the UI and for everything that I use a computer for, Mac has worked just fine: I’ve never found myself needing to execute an exe or run some massive game.

So, I bought the 256GB/8GB RAM M1 Mac Mini as a replacement for my beloved iMac. And it only cost $699, which is a great price point for any computer, especially the power of the M1. The M1 is amazing. I haven’t heard the fan once in the year of using it. It runs all my applications so smoothly, and the internal SSD makes booting up not so painstaking.

Apple offers multiple configuration options, such as 16GB RAM ($200), 512GB SSD ($200), 1TB SSD ($400), and a 2TB SSD ($800). It doesn’t take an expert to realize Apple’s pricing for their upgrades are ridiculous. Obviously, I opted out and stuck with the base model. In hindsight, I should have went with 16GB RAM to future-proof my Mac Mini, as the RAM is soldered on, making it impossible to upgrade without desoldering.

When I bought the Mac Mini, I also bought a SanDisk extreme portable SSD with 1TB capacity for like $60 off Amazon. Crazy, 1TB SSD for $60 compared to Apple’s $400. However, I never got around to making the SSD the primary boot device as my initial plans were to just use it as a drive for all my documents and files, and keep all applications and supporting files on the internal drive. However, I decided to change that when I upgrades to MacOS Monterey and noticed I only had 100GB left of storage. In just a few applications and MacOS updates later, that available storage would be non-existent. So, I went to figure out how to make my external SSD the primary startup disk for the Mac Mini.

The Process

This took a little (lot) of effort. It isn’t hard, necessarily, I just encountered a lot of mishaps along the way. First and foremost, a lot of the tutorials I found online explained to download MacOS to the external SSD from Recovery Mode/Disk Utility and boot from the SSD. However, that didn’t assist in copying all existing files from my internal drive over. That just created a clean MacOS installation. After some further research, I found three viable options to copy(clone) my MacintoshHD internal drive to my external SSD. 1) Mac’s DiskUtility, 2) CarbonCopyCloner, 3) SuperDuper!. I started with DiskUtility as I trusted Apple’s own disk cloning than a third-party. However, each time I tried, I got an error while writing to the SSD. I believe it to be because I had FileVault enabled on the internal drive, and when in Recovery Mode, MacintoshHD is encrypted, and thus, you can’t clone it properly. So, I downloaded CarbonCopyCloner and tried that. While it did create a bootable clone, it introduced me into a boot-loop: continuously turning on and off, and would never boot into MacOS. So, I tried one last hope: SuperDuper! And this one actually worked. It was more intuitive to use than CarbonCopyCloner, and it created a bootable drive that didn’t just get me stuck in a boot-loop. As a precaution before booting into the external drive, I did disable System Integrity Policy (SIP) as I was receiving messages about kernel panic from third-party extensions after the failed boot-loop from CarbonCopyCloner; so I figured allowing those extensions would remove the risk of a kernel panic with my SuperDuper! clone.

Creating a bootable external SSD

All-in-all, here are the steps I took to create a bootable SSD drive and set it as the primary startup disk on my M1 Mac Mini:

  1. Connect your external SSD to your Mac via Thunderbolt3/USB-C.
  2. Download SuperDuper!
  3. Set “Copy” to MacintoshHD and “to” to your external SSD.
  4. Set “Using” to “Backup all files”
  5. Select “Copy Now”
  6. After SuperDuper! is done copying, boot into recovery mode by first powering off your Mac and then by holding the power button until you see “Loading startup options.”
  7. You should see your external SSD, MacintoshHD, and Options. If you do not see your external SSD, it did not clone properly and you should repeat the steps above.
  8. Select “Options.”
  9. Access Terminal by selecting “Utilities->Terminal” from the top bar.
  10. Type “csrutil disable” to disable SIP.
  11. Access Startup Security Utility by selecting “Utilities->Startup Security Utility” and select Permissive.
  12. Power off your Mac, and boot back into recovery mode, this time selecting your external SSD.
  13. When booted in, go to System Preferences->Startup Disk, and select the external SSD as your default startup disk.

Once everything is done, your Mac will automatically boot into the external drive.

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