Imac will not boot up - help!

placeholder · 19 Apr 2020 at 15:01

Following on from the thread about inheriting an old iMac today Ive run into a major problem. I was using it online with no issues (its been flawless since I got it) when all of a sudden whatever site I was on wouldn't load the link I was clicking on. I initially thought my internet connection had dropped out but checked and all other devices were working. I just decided to reboot the machine. When rebooting I got to the apple logo with the bar beneath showing progress, all going fine when after abut 10 seconds it shut down. Screen goes instantly black. Every time I switch it on this now happens.

I have tried command R and I can get into the recovery system but that's about it. Even trying to do a fresh install runs into issues because it says the disks are locked.

Does anyone have any help or advice they could offer. Im not hugely technically minded with this sort of stuff. Would like to avoid a reinstall if possible but will do it if required.

Alpherah · 19 Apr 2020 at 15:50

try holding cmd+opt+P+R when you turn the machine on, keep holding until the second chime

otherwise next step is to erase the drive.

Cmd+R, disk utility - select the drive and erase.
It will ask to format - select either OSX Journaled (for older versions of Mac OS) or APFS (for newer ones) then install Mac OS (disk will no longer be locked)

visibleman · 19 Apr 2020 at 15:53

Use internet recovery (CMD + ALT + R iirc) instead and then try a reinstall/restore there.
However, when i had something similar happen i ended up having to erase the complete drive (make sure you select the drive within Disk Utility and not just partitions) before i reinstalled MacOS.

Edit - As @Alpherah mentions, a NVRAM/PRAM reset is a good shout before doing a reinstall. Similarly, you can do the SMC as well for good measure - https://www.macworld.com/article/2881177/how-to-reset-a-macs-nvram-pram-and-smc.html

Alpherah · 19 Apr 2020 at 16:28

visibleman said:
Use internet recovery (CMD + ALT + R iirc) instead and then try a reinstall/restore there.
However, when i had something similar happen i ended up having to erase the complete drive (make sure you select the drive within Disk Utility and not just partitions) before i reinstalled MacOS.

Edit - As @Alpherah mentions, a NVRAM/PRAM reset is a good shout before doing a reinstall. Similarly, you can do the SMC as well for good measure - https://www.macworld.com/article/2881177/how-to-reset-a-macs-nvram-pram-and-smc.html

smc worth a shot, shouldn’t be any difference using internet recovery as the drive is locked regardless.
Internet recovery will be used if you have a fusion drive installed however ...
And enjoy the re-making the fusion

visibleman · 19 Apr 2020 at 16:43

Alpherah said:
...shouldn’t be any difference using internet recovery as the drive is locked regardless.

True true. Only reason i mentioned it was just in case the recovery partition has borked itself so an Internet Recovery (or ideally MacOS USB Installer) usually sorts that.

Good point about splitting of Fusion drives; luckily diskutil (command) now includes the option of repairing it although Apple does list step-by-step instructions for manually repairing within the support pages somewhere.

Edit - Purely for reference for OP or future users - https://support.apple.com/en-gb/HT207584

@placeholder, let us know how you get on; you should be able to sort it with one or a combo of the solutions above

Alpherah · 19 Apr 2020 at 17:11

I can’t remember which year it was -
But the first iMac with fusion drives can only be remade manually which is a right ball ache each time

dirtybeatfreak · 19 Apr 2020 at 20:52

If it's an older OS (ie not AFS format) then get a copy of Diskwarrior and boot from it and rebuild/verify the drive. Also try repairing permissions button.

placeholder · 20 Apr 2020 at 10:34

Thanks for all the suggestions. Only command R seemed to work for me so options were limited. In the end I just erased the disk and did a fresh OS install which seems to have worked. Fortunately I didn't really have anything too important on it so haven't lost anything of value. Needless to say that its prompted me to sort out automatic back ups etc and means I don't have and files cluttered on it now either. Might as well make the best of it.

Feek · 20 Apr 2020 at 12:45

Time Machine, it couldn't be easier, especially on an iMac. Just plug a USB hard drive in, set it up and forget about it.
For boot and braces, have a second hard drive connected and run a nightly backup using either SuperDuper! or CarbonCopyCloner.

I do both!

placeholder · 20 Apr 2020 at 19:44

Feek said:
Time Machine, it couldn't be easier, especially on an iMac. Just plug a USB hard drive in, set it up and forget about it.
For boot and braces, have a second hard drive connected and run a nightly backup using either SuperDuper! or CarbonCopyCloner.

I do both!

Yup, got Time Machine all set up now which was something I should have done at the very start, wise after the event as usual!