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I could use some help/advice on a problem I have with my iMac (late 2012 iMac running Mojave).
Recently, my iMac would not wake from sleep mode. After a hard shutdown, it took many hours (over 12?) to reboot and operated extremely slowly and again could not wake from sleep. I tried rebooting in Safe Mode (better, but still slow and then what?)and a PRAM reset. Running the disc utility repair option did not indicate any problems. I am able to boot up the computer from my SuperDuper backup on an external drive but unable to boot up from the internal hard drive.
Should I erase the hard drive and reinstall the OS? If I do this, can I reinstall the OS from the SuperDuper backup (or simply copy the external drive onto the hard drive?). Any other ideas or options? I'm far from an expert on Macs and the idea of erasing the hard drive makes me nervous but I'm not sure what else I can do. Any advice is welcome - Thank you!
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I am assuming you do not have a full HDD - like you need 10% of the capacity empty. If that is not the case - first item is clean things up. Look at downloads folder. Empty Trash. Look at Applications.

I would perform a hardware check -- here is a link to Apple's software for checking hardware. I have not used this, but I expect such a test will take some time. Guess I am wrong - Apple says this takes minutes.

https://support.apple.com/en-us/HT201257
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You have a number of symptoms, each of which can arise from separate problems or be related.

What does the screen show when you are "unable to boot up from the internal hard drive"?

Do you have peripherals attached, and have you tried booting from the internal drive with all peripherals removed? If your iMac is fine with peripherals detached, you have a hardware problem possibly related to the ports, or maybe you have a driver issue.

You tried Disk Utility, but have you tried Apple Hardware Test (https://support.apple.com/en-us/HT201257)? Did you check the SMART indicator on Disk Utility? Have you tried a disk utility program that scans deeper, e.g. TechTool Pro?

If you have bad sectors on your hard drive, Disk Utility won't flag them (though maybe SMART will). If you have bad sectors, don't bother reinstalling from SuperDuper -- the drive itself is corrupt and has to be replaced.

-awlabrador
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GWPotter - My HD is only about 50% full. What should I be looking for in downloads or applications? I will try the hardware check. Thanks!
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awlabrador - when I say unable to boot from the internal drive, what happens is that I get stuck on the opening white screen with the grey apple logo and progress bar. It takes a long time for the progress bar to reach the end (an hour?) but then gets stuck there for hours (I didn't have the patience to let it sit overnight again when I tried last night so I rebooted from the BU drive and it works fine).
I had removed all the peripherals except for the BU drive; I can try removing that as well. I'll also try the Apple Hardware Test.
I had an old version of TechTool Pro but I'd need to buy an updated version. Is that recommended or are there better options?
Thank you for the suggestions
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I could use some help/advice on a problem I have with my iMac (late 2012 iMac running Mojave).
Recently, my iMac would not wake from sleep mode. After a hard shutdown, it took many hours (over 12?) to reboot and operated extremely slowly and again could not wake from sleep. I tried rebooting in Safe Mode (better, but still slow and then what?)and a PRAM reset. Running the disc utility repair option did not indicate any problems. I am able to boot up the computer from my SuperDuper backup on an external drive but unable to boot up from the internal hard drive.



It sounds like other one of your kernel files is corrupt or your HDD may be biting the dust. IIRC, the hardware check that Gordon gave you also covers HDDs. You can also try simply reinstalling the OS. The reinstall would be my first thing because if it is simply a corrupt kennel file, the reinstall should overwrite it.

HTH,
Kathleen
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It sounds to me like you have a seriously corrupted HD. If Disk Utility doesn't catch things, then I'd suspect it's bad sectors, which means you'd have to replace the HD. The age of your iMac increases the likelihood of a corrupted drive.

SMART may have caught bad sectors. In Disk Utility, right-click or ctrl-click the drive, select Get Info, and scroll to see if there's a SMART status indicator and whether there's some issue flagged. If it's not supported on your machine or drive -- likely, I assume, since it's a 2012 iMac -- then you can try a bad sector scan via TechTool Pro or some other utility. You'd have to boot from an external flash drive or other drive to run it. It doesn't hurt to upgrade to a new TTP license, IMO.

If it's just a filesystem issue, I'd have expected Disk Utility to flag and correct it, though it doesn't catch all filesystem issues, in my experience. Other utilities like TTP can catch and fix issues that Disk Utility doesn't. Sometimes the Mac utilities fail to fix such issues, and I've found some success with Windows utilities (or just Disk Management) when those fail. Kathleen suggested a corrupted kernel file, but I put those at the same level of likelihood and repairability as filesystem corruption.

On the other hand, if it's a bad sector issue, it's time to replace the drive. Those never get better. A secure wipe via Disk Utility can sometimes remap the sectors, but in my experience, it's never worth it -- bad sector issues tend to spread. In fact, I have an external USB drive on my desk right now for which I tried -- twice over a month -- to remap. Each time, the drive was "fixed", only to have more bad sectors pop up again very soon afterward. It wasn't worth the attempts to remap the drive, in my opinion.

-awlabrador
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A 2012 iMac? Even if you could figure out how to get it working again, it's lived a long, full life, and it's time to get a new machine that can run the latest OS and apps. It's a world of difference.

About 6 months ago, I was in the same spot you're in now. I hate to spend $. But I got a nice MacBook Pro (no silly touchbar and super-duper retina screen though) and I have never regretted it.
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Disc Utility says that SMART status is not supported on this drive.
I was unable to get to the Apple Hardware Test - holding the D key at start up brought up a white screen with a spinning globe and asking to select a wifi network. My wifi was not listed on the dropdown; there was an option to enter my wifi name & pw but I was unable to log into it (?? - it was working properly).

If it is a bad drive, is it replaceable and is it worth it for an older iMac?

MisterFungi - You may be right. Any idea if this is a "typical" lifetime for an iMac? While a new iMac would be nice, I'll first consider cheaper options if viable. For the immediate term, it works fine while booted to the backup drive but that is not a long term solution.

I appreciate all the suggestions. My iMac is a home computer and I know a minimal amount on how to diagnose problems so this has been informative.
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If it is a bad drive, is it replaceable and is it worth it for an older iMac?

Depends upon how handy you are:
https://www.ifixit.com/Device/iMac_Intel

I don't know how much work you do on your own systems, but iFixIt has guides on replacing HDDs, logic boards, tons of stuff. Basically, if it is replaceable, they have a guide for it.

Kathleen
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Any idea if this is a "typical" lifetime for an iMac?

A $1,500 Mac held for 5 years is $25 a month
A $2,100 Mac held for 7 years is $25 a month

A BARGAIN. Technology is advancing so fast that updating old gear is penny wise, pound foolish.

Denny Schlesinger
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Denny

Thanks. I was asking about "typical" iMac life out of curiosity as I have no idea what is expected in terms of a working life before a hardware failure. I'm sure I've gotten my money's worth.

On the other hand, the iMac is way more computer than I need for my modest home use. I don't use the Mac for anything that requires a lot of speed or processing power so I'm in no rush to replace or update unless I need to.

l
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Seven years is not especially soon for something to go bad, particularly a hard drive. I would say it's about average. But Macs can last years longer. I just replaced a 9 year old Mac Mini that was still working but no longer did what I needed.

I agree with other posters that reinstalling the OS is first step. https://support.apple.com/en-us/HT204904

If that doesn't work and you want to try to keep it running for as little as possible you can run it by booting from an external drive. You can test this plan by booting from the SuperDuper drive and use it for a while and see if it works or is too sluggish. Beware, if use the SuperDuper drive you will not have a second backup. Running from the SuperDuper disk will test if it really is the hard drive that's the problem. If you like this route and don't have a spare drive lying around you can get 1TB external hard drive for about $50.

Replacing the internal hard drive is doable but is not a simple repair and probably best to do yourself only if you are experienced. You could call some local places to find how much they would charge to replace the drive. I'm guessing it will cost $300. I probably wouldn't spend that on a 7 year old iMac. Also, the late-2012 is now officially "obsolete" which means Apple no longer guarantees that parts will remain available.
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Update: I reinstalled macOS but could not get past the login screen. I rebooted from my backup drive and installed the latest techtool pro. The hard drive failed the surface scan (~1600 bad blocks). So I guess I'll soon be shopping for a new Mac. Thanks again for all the help.

Now, whether to simply replace my iMac w/ the comparable current base model or treat myself to a 27" upgrade....
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Now, whether to simply replace my iMac w/ the comparable current base model or treat myself to a 27" upgrade....

Treat yourself.

-awlabrador
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