Erased my OS by mistake.

[AndyJ2024]

I have somehow erased my iOS operating system off my iMac 27! I had followed a few YT videos, but still screwed up!

Currently, I have on screen .. a white screen with a grey ‘no-entry’ sign in the middle. I cannot get passed that screen, and I’ve tried everything possible on apple support and further YT videos, with no success!

Can anyone help me restore please?
Much appreciated.

Andy

 

[HobeSoundDarryl]

It's macOS not iOS on iMacs.

You don't identify the specific iMac or macOS OS. But basically it's a simple matter of reinstalling the appropriate macOS version for you iMac and then reloading your personal files from (hopefully) a backup, ideally a Time Machine backup or similar.

Here's Apple's instructions for installing macOS.

If you have a Time Machine backup, you can do what is called "Restore" also described on that page.

If any of that feels a bit complicated, schedule an appointment at an Apple Store and they can help you do these things.

If by "no entry", you mean the screen shown here, you need to do the 4 steps described on that page... or, again, head for an Apple Store and get their help.

 

[antiprotest]

What were you trying to do that got the OS erased?

 

[AndyJ2024]

It's macOS not iOS on iMacs.

You don't identify the specific iMac or macOS OS. But basically it's a simple matter of reinstalling the appropriate macOS version for you iMac and then reloading your personal files from (hopefully) a backup, ideally a Time Machine backup or similar.

Here's Apple's instructions for installing macOS.

If you have a Time Machine backup, you can do what is called "Restore" also described on that page.

If any of that feels a bit complicated, schedule an appointment at an Apple Store and they can help you do these things.

If by "no entry", you mean the screen shown here, you need to do the 4 steps described on that page... or, again, head for an Apple Store and get their help.

Thanks for the correction, auto-correct huh! I’ve tried all that thanks though.

 

[Ben J.]

Startup key combinations for an Intel-based Mac:
Command (⌘)-R: Start up from the built-in macOS Recovery system.
Or use Option-Command-R or Shift-Option-Command-R to start up from macOS Recovery over the internet.

 

[Fishrrman]

OP:

What I'd suggest first is to boot to internet recovery and then do an OS install WITHOUT erasing your internal drive.

Here's what to do:
Power down, all the way off.

Press and hold all at once:
Command-OPTION-R
... and (while still holding them) press the power on button.

DON'T LET GO OF ANY OF THOSE KEYS!

If you're connected to the net via wifi -- let go and enter your wifi password when requested.
If you're connected via ethernet -- let go when you see "the spinning globe" that indicates the internet utilities are loading.

It takes a little while for the utilities to load, so be patient.

When done, you will either see the internet utilities pane
or
It may put you right into the OS installer.

You want to open the installer (if it doesn't open automatically).

My recommendation is that you accept whatever version of the OS the installer offers you.
A Mac that boots (any version of the Mac OS) is better than one that won't boot at all.

Start clicking through. The installer will probably ask WHERE to install, just point it at your existing location (the OS that won't boot).

The Mac will reboot several times, and the display will go dark for a minute or more with no other indication of activity. Be patient.

When done, you should either see your old login screen, or perhaps there will be a few things to "click through". You -should- be able to get back into your account and access your data.

Good luck.

Remember:
Command-OPTION-R
for internet recovery...

 

[FreakinEurekan]

@Fishrrman's got it right - Command-Option-R for any Intel Mac from 2012 to 2020.

The only thing I'd add, before the reinstall, is:

1. Open Disk Utility
2. View menu > Show All Devices
3. Select the primary disk (usually called either "Apple SSD," "Apple HDD," or "Fusion")
4. Erase
5. Scheme: GUID; Format: APFS; Name: Whatever you like, but "Macintosh HD" is most common
6. Disk Utility menu > Quit Disk Utility

Then proceed with reinstall.

Yes, in many instances this isn't necessary. But it takes a minute or less, and heads off some potential "Gotchas" that you might not find until after the hour-plus install is complete, and has to be re-done. I think it's worth the effort.

 

[AndyJ2024]

Thanks guys, but as I said in my original post, I’ve tried everything that you can find in apple support and other sites.

 

[iStorm]

I feel like we're not getting the full story here...

• Were you actually trying to do something - like reinstalling macOS or messing around in Disk Utility...and then it quit working?
• Were you trying to fix another problem before this happened? If so, what was that?
• Or did it just randomly quit working one day? (And you thought you accidentally erased it?)

This screen means the OS cannot be found, but it could also be that your hard drive failed and is no longer working. Try running Apple Diagnostics. You can do this by holding the 'D' key while booting up. If that doesn't work, then try 'Option-D'. If it still doesn't work, try plugging the keyboard into the Mac. (I'm assuming you're using the Magic Keyboard.)

Use Apple Diagnostics to test your Mac - Apple Support

Apple Diagnostics, formerly known as Apple Hardware Test, can check your Mac for hardware issues.

support.apple.com

Thanks guys, but as I said in my original post, I’ve tried everything that you can find in apple support and other sites.

What exactly isn't working? Are you not even able to boot into recovery from the suggestions above?

 

[Fishrrman]

The OP's problem above illustrates why EVERY Mac user (at least on Macs built prior to the introduction of Apple Silicon) should have at least one BOOTABLE external drive (preferably a cloned backup).

If the OP had one, he could probably be back up and running in a couple of minutes (unless it was a hardware problem that prevented the Mac from booting regardless of which drive was used).

 

[Mr.Fox]

I have somehow erased my iOS operating system off my iMac 27! I had followed a few YT videos, but still screwed up!

Currently, I have on screen .. a white screen with a grey ‘no-entry’ sign in the middle. I cannot get passed that screen, and I’ve tried everything possible on apple support and further YT videos, with no success!

Can anyone help me restore please?
Much appreciated.

Andy

Good thing they only removed the operating system, not threw the computer out the window. Probably got tired of the YouTube ads )))

 

[Mr.Fox]

What were you trying to do that got the OS erased?

Probably saw the video in 144p, so the hand trembled ))))

 

[dumastudetto]

You don't have to go to such extremes to delete your browser's internet history.

 

[960design]

Thanks guys, but as I said in my original post, I’ve tried everything that you can find in apple support and other sites.

If your iMac failed to reinstall via internet (Shift-Option-Command-R) one of the following is true:

1. Your keyboard is broken
2. Your internet is broken
3. Your iMac is broken
4. You are broken