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Boot failure

My Mac Mini has had a hissy fit and won't boot. I've tried Safe mode, system check, resetting the Pram, and Hardware Test, but all I get is a partial boot on a mint/grey striped loading screen before it all goes black. In recovery mode I can get past that to a white screen but then it hangs (it successfully booted the first time I tried that, but then went phut before I could reconnect my external drive to backup recent files - if I could even get that again it would help!)


What else can I try?


NB: The last time I had trouble, five years ago, I wasn't clued up enough to try any of the above. The local Genius Bar replaced my hard drive as a first resort, but then it turned out the problem was the motherboard and I needn't have sacrificed the lost data after all.

Posted on May 26, 2020 7:01 AM

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Posted on May 30, 2020 9:55 AM

Boot recovery (or internet recovery, and with most current version, using Option-⌘-R ) and try to install macOS or restore your backup onto an available (empty, can be erased) storage device, and boot that.


This to test whether the internal storage is failing (in isolation), an external hard disk allows operations (with degraded I/O performance), and can verify that the rest of the problematic Mac is working.


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May 30, 2020 9:55 AM in response to MoArrows

Boot recovery (or internet recovery, and with most current version, using Option-⌘-R ) and try to install macOS or restore your backup onto an available (empty, can be erased) storage device, and boot that.


This to test whether the internal storage is failing (in isolation), an external hard disk allows operations (with degraded I/O performance), and can verify that the rest of the problematic Mac is working.


May 26, 2020 7:38 AM in response to MoArrows

Run diagnostics or hardware test. See if that identifies any issues.


Boot recovery (or internet recovery, and with most current version, using Option-⌘-R ) and try to install macOS or restore your backup onto an available (empty, can be erased) storage device, and boot that. This’ll tell if your internal storage has failed, or if there’s some other issue.


Hard drives are one of the most typical failures here, though many other sorts of failures are possible.

May 30, 2020 1:45 AM in response to MoArrows

Update:

I got hold of a FireWire and tried to do an external boot in Target mode from my even older iMac. It didn't work, per se, probably because it's a different processor, but the attempt somehow unblocked the Mini's OS long enough for me to run Disk Utility again and back up my data. I then restarted the machine and it worked perfectly all of yesterday evening.


This morning it's screwy again. It doesn't boot, or it boots for a few minutes then hangs/pinwheels, or the display goes off centre or it part-boots to a white screen.


The hard disk still seems to be fine though, everything's still there. Do I need a new circuit board or something?

May 30, 2020 1:49 PM in response to MoArrows

So to confirm, you have re-installed macOS on an external storage device, and then booted from that external storage? Was that then stable? I'm here not suggesting reloading onto nor booting from your internal storage, I'm suggesting a means to use external storage to test whether the internal storage is failing.


Something here has very clearly failed, it very clearly involves the internal storage, and the question then becomes whether it's the internal storage device, or the I/O hardware that connects to storage, or some other core part of the Mac that has failed, is unclear.


To differentiate a failure isolated to the internal storage device from a failure elsewhere in the Mac, installing on and booting from an external storage device can be a useful test. And it can allow continued operations, while repairs are organized. If the failure is not isolated to the internal storage device, then repair costs increase, and external storage may not or will not work reliably.


May 31, 2020 5:41 AM in response to MrHoffman

I don't have an external device capable of installing a new OS from the internet. What I have is a storage brick, and it is not empty: it's got all the stuff I retrieved from the malfunctioning machine and more that was on it already.


I may end up having to buy a new Mac, but I'm not doing it *just to test the one I've got*.


Can you explain why you have this idee fixe that the malfunction is definitely on the hard disk, even though I've established that the hard disk is okay and the data on it is even accessible when the machine stays on long enough?


May 31, 2020 1:10 PM in response to MoArrows

I’m focusing on the hard disk here because a failure of the hard disk can manifest as reported here including sometimes working and sometimes not working, and because it’s also one of the few components here that can–given available external storage, which is unfortunately not available here–be bypassed and tested separately, and because external storage can be repurposed for backups and other uses.


You’re headed for a repair or replacement, yes.

Boot failure

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