A few days ago, after my 12-inch MacBook running the latest Sierra became sluggish, I restarted. After entering my account password, my Mac showed a white progress spinner that uses “spokes”—the kind of spinner you usually see at shutdown—would appear for several seconds, then disappear, replaced with a cursor that couldn’t be moved with the trackpad. This would recur over and over for hours.
I’d had a similar sort of problem crop up once during beta testing for software that I don’t want to mention the name of, as the issue was resolved for those of us on the cutting edge and the particular release of software is no longer in development. In that case, the spinner would appear and disappear, but no cursor, and much more rapidly. I contacted the former developer and followed his instructions to use Recovery and Terminal to remove all relevant files, but that didn’t solve this problem. Without the software installed, something else still triggered this slightly different behavior.
I went through a litany of options, including, after asking for advice on Twitter, ones I hadn’t considered:
- I could boot into Recovery (Command-R after startup or restart), so I booted into it and ran Disk Utility. The disk checked out fine.
- I booted into single-user mode and used the command-line tools to check for problems, and again, nothing emerged. After exiting into an interactive session, the same spinner issue cropped up. None of the errors I could find helped diagnose the problem.
- Safe mode didn’t bypass the point after login where the blockade happened, so it wasn’t of use.
- In Recovery, I reinstalled Sierra without erasing the disk. Same problem.
The one thing I didn’t remember to try, and wish I had, was attempting to screen share from another Mac—or even using SSH (remote secure Terminal-style access) to see if I could access the system while things were failing.
I began to wonder if it weren’t a video-card or GPU problem instead of a system problem. Apple and other computer makers engage a simpler mode in their graphics system at boot time, and then fire up the full power once the OS has initialized. Apple’s safe mode, for instance, disables accelerated graphics, for instance, which can cause video glitches.
To isolate whether it was hardware or the OS, I decided that since the disk was still reachable, I’d perform a full clone via Recovery using Disk Utility. Here’s how you do that:
- Connect an external drive.
- Boot into Recovery (Command-R).
- Click Disk Utility in the list that appears and click Continue.
- (Optional) If you have FileVault enabled, select your partition, and click Mount. When prompted, enter any administrative password.
- Select the startup drive and then choose File > New Image > Image from “Partition Name.”
- Choose the external drive as the destination.
This operation creates a mountable but not bootable clone as a disk image. Then I used Disk Utility to erase the drive. Unfortunately, this erased the Recovery partition, too! On restart, the Mac reverted to Internet Recovery, where it downloads the Recovery software and then installs and launches it. I used Disk Utility to restore my startup drive from the clone, figuring that might have cleared the condition.
(In Disk Utility, select the startup drive, click Restore, and then click Image to select the image. Some clones might not work in image form, but Disk Utility mounts them, and then you can select the mounted clone as the source for a restore.)
Restoring resulted in the same problem, so whatever the issue was, it was embedded in the particular system I had installed.
I went back and booted into Recovery, and erased the drive again and installed macOS. Because of the age of the machine, its Internet Recovery partition loaded El Capitan. (If you have Sierra’s Recovery software installed, as of 10.12.4, you can force either the oldest compatible OS X/macOS to load or the very latest depending on whether you press Command-R or Command-Option-R. Because I’d erased the Recovery disk, Internet Recovery installed the version that the computer shipped with.) The Mac booted fine into El Capitan release, so I ran the Sierra update separately, which also worked. This made a hardware fault seem unlikely.
Instead of restoring again, I ran Migration Assistant, and selected my cloned disk image as the source. I selected everything offered for migration. Several hours went by, the machine rebooted, and…I was back again to cursor/spinner/cursor/spinner.
I decided to try one more thing before throwing myself on the mercy of the Genius Bar. (The next appointment when this all started was about five days later, so I hadn’t yet seen Apple.)
I erased the startup partition (not the drive) and reinstalled Sierra. Then I used Migration Assistant to import just Applications, my user account, and Computer & Network Settings. This time, I unchecked Other Files and Folders, assuming that this is where the trouble lay if it were system related. Since I had a full clone, I could resuscitate any missing items later if necessary.
This time was the charm. I had to re-login into various services (Apple and otherwise), retarget Backblaze to the “new” drive with the same name, and allow a bunch of system-level behavior through the Security & Privacy system preference pane’s Privacy tab. I also had to re-enable FileVault, which is not in effect after erasing a drive, as it has to be set up while running macOS.
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