HELP: trying to wipe iMac and install latest OS

[philbrown]

iMac 12,1 i5 2.5 GHz
I'm trying to:
1. wipe the hard drive
2. Install the latest system for this machine, which is either 10.12 or 10.13 depending on which article you read.

Apple has made this simple operation incredibly difficult. All I want to is wipe my wife's old computer and set it up as a valid spare for my studio Mac Pro "just in case".

What a nightmare. I'm about 6 hours into this with no luck whatsoever. Read a bunch of articles, tried to create a bootable installer, tried upgrading from the iMac itself and a lot of other things that are a blur.
I get this error when trying to create a bootable 10.12 installer:
The selected item does not appear to be a valid macOS Installer.
It is lacking the file "Contents/SharedSupport/InstallESD.dmg"

The 10.12 installer when attempting to install from the iMac itself wanted the machine at 10.7.5 so I tried installing 10.7.5 and that wanted 10.7... and so it goes around in circles, to quote Billy Preston.

Any help is very much appreciated!

[CharlzS]

Don't know if available on your machine, but did you try the online recover option?
https://support.apple.com/en-us/HT20131 ... %20More%20

Also, if you have access to your app store account, older versions of the OS full install that were updated via the store can be downloaded there.

Here's a link to several full installers.
https://osxdaily.com/where-download-macos-installers/

[philbrown]

Don't know if available on your machine, but did you try the online recover option?
https://support.apple.com/en-us/HT20131 ... %20More%20

Thanks for your reply.
I guess I don't understand how the above will help me with this specific issue. I don't need to reinstall what's already there.

Also, if you have access to your app store account, older versions of the OS full install that were updated via the store can be downloaded there.

Here's a link to several full installers.
https://osxdaily.com/where-download-macos-installers/

Those are the same installers I've been trying to make work over and over. I forgot to mention I tried installing from my Macpro > iMac in Target disk mode, but that didn't work either.

[mikehalloran]

An iMac 12.1 should be a 2011. High Sierra is your last OS.

Best method is to make a USB install drive using the 10.13.6 installer. Boot from that. Use Disk Utility to erase and format your drive APFS — hopefully, you have thrown away the original HDD and have installed an SSD but if your HDD is still good (highly unlikely) it can be formatted APFS with the 10.13.6 installer. Now the OS will install correctly. Migrate your data from your Time Machine backup — you have one, right?

[mikehalloran]

Don't know if available on your machine, but did you try the online recover option?

Not an option for this machine. It shipped with OS 10.6.4. Internet Recovery is unavailable to any Mac that did not ship with OS 10.7 or later.

I have the 10.6.4 disk image but that’s not needed here.

The method I outlined will work. I did it just a few days ago, in fact. I can make a working install stick for cost and postage if you need one or can post the correct method here.

My wife’s 2011 has been running High Sierra for nearly three years. These are the easiest iMacs to open and replace the drives. Need a few tools, an SSD, an adapter, the OWC Temp sensor, a CR2032 battery and some time. Takes me 20 minutes one-handed but I’ve done many by now.

[philbrown]

Thanks for your help and info, Mike. Your vast knowledge is always appreciated.

[monkey man]

Indeed.

[mikehalloran]

If you know how to create an installer, it goes through the process, you can select in an Option–boot but you get Ø instead of booting, you have one of those USB sticks that can't boot your Mac. I got a batch of inexpensive 8GBs once and had to return them to Best Buy. Otherwise, anything 8GB or larger works (16GB for Catalina).

Here's how I do it:

How to Make A Bootable USB Disk of OSX

Have a backup. Time Machine or your old Mac is fine as long as the backup is not a newer OS than the one you are trying to install.

Download the correct complete installer. When it tries to run (or tells you it's too old to run on your Mac), Quit. The installer will now be found in your Applications folder. Leave it there.

Insert your 8GB or larger USB external stick/drive. Change the name to MyVolume. This is important or the following Terminal Commands will not work. This process will erase, reformat and rename the drive to that of the OS installer.

Launch Terminal from /Applications/Utilities and enter the command below (copy & paste) and then your password when prompted.

High Sierra
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ High\ Sierra.app


Mojave
sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Mojave.app



Catalina
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Catalina.app

[philbrown]

If you know how to create an installer, it goes through the process, you can select in an Option–boot but you get Ø instead of booting, you have one of those USB sticks that can't boot your Mac. I got a batch of inexpensive 8GBs once and had to return them to Best Buy. Otherwise, anything 8GB or larger works (16GB for Catalina).

Interesting, and I've never heard that before. That may have been part or all of the problem.

Download the correct complete installer.

That seemed to be the rub. I followed link after link that were all supposed to be complete installers but then ended up being updaters or just wouldn't work. Apple blocks you at every turn making things as difficult as possible.

On another slightly related note, my home life is unraveling at the moment. Severe water damage to our house, kitchen demolished and they're getting ready to take out most of the flooring in our house amongst many other issues right now. Probably be December before we have a kitchen and floor again. I got another computer cleaned up enough to use for a backup and have had to shelve this iMac project for the time being.

Again, thanks for your help, but I am not able to deal with this right now.

[monkey man]

Sorry to hear that, Brother Phil.

Laura took a dump on you by the sounds of it.

[philbrown]

Sorry to hear that, Brother Phil.

Laura took a dump on you by the sounds of it.

Thanks, brother.
It was a dishwasher that had been leaking for years, unbeknownst to us.
Amazing chain reaction damage from that one thing.

[mikehalloran]

I followed link after link that were all supposed to be complete installers but then ended up being updaters or just wouldn't work.

When it's time, I can help with that. Being Apple, there's mystic mumbo-jumbo involved in getting the updater to download — even with the right link.

[Phil O]

This is slightly off topic, but I'm looking for instructions for creating an external bootable disk (not installer disk, but a full boot volume with apps, etc.). I thought Mike had instructions on this in another thread, but I couldn't find it.

I've found some conflicting instructions on line, but can't seem to get any of them to work.

Your friendly neighborhood Phil

[Phil O]

Sorry to hear about your kitchen, Phil. I had a similar thing happen in my bathroom. There was a hairline crack in the toilet creating a leak so slow that it did not reveal itself until the floor under the tile was badly damaged. Had to rip it all out.

When life gives you lemons, rip out the floor.

[mikehalloran]

This is slightly off topic, but I'm looking for instructions for creating an external bootable disk (not installer disk, but a full boot volume with apps, etc.). I thought Mike had instructions on this in another thread, but I couldn't find it.

I've found some conflicting instructions on line, but can't seem to get any of them to work.

Your friendly neighborhood Phil

Easy if the same OS or newer as the Mac you’re installing from: Download the installer. Install the OS onto the external drive (you may have to format it in Disk utility first). When done, it should boot automatically from the external drive. Use Migration Assistant to move the data, apps and settings over.

Not so easy if you want to install an older OS. Make a USB installer. Install the OS onto the external drive. The drive will boot automatically. If you have an old Time Machine backup with that old OS, you can restore from that. Now you can move your work files over from the other Mac or a current Time Machine backup—let them overwrite. Use Migration Assistant but select Data only. If you don’t have an old backup, you can move any Apple Apps over without reinstalling but you’ll have to reinstall any other apps. Again, move your work files over (Documents, music etc.) — if Migration Assistant will let you import data only, this will save you from having to zip your old files first (Office and DP among others).