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Model A1311 / Late 2009 / 3.06 or 3.33 GHz Core 2 Duo processor

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iMac OS USB install problems, Yosemite to High Sierra

I have a Late 2009 iMac that i purchased second hand in 2015. I am trying to upgrade the OS from Yosemite (10.10.x) to High Sierra. The install fails, and I have spent days trying to find a workable solution. Yosemite was on the machine when i bought it, and I doubt if it's listed in my appstore purchases (it was bought second hand).

Initially i backed everything up onto an external HD (no Time machine backup), downloaded the High Sierra.app installer (the small partial one), and ran it hoping that the upgrade would just work. During this process the full installer downloaded, the system restarted, and it stopped with the error "MacOS couldn't be installed on computer. Installer resources couldn't be found." At this point I created the USB installer via terminal (createinstallmedia) on a 16GB stick. I created the USB from the .app applicationpath and following the instructions from part (b) discussed here:

https://chriswarrick.com/blog/2020/06/03...

The only notable mention is the step of copying the contents of the full Install directory into the Contents/SharedSupport/ dir. Anyway the USB successfully created. I booted into recovery mode, and formatted the destination disk as Extended (Journaled) with GUID scheme per the usual instructions. Now when i boot to USB (holding Option, which goes automatically to Recovery screen), i select "Install MacOS" option, click Continue, and then nothing happens. The machine isn't frozen, it just doesn't advance into the installation.

I open terminal and poke around. I try

hdiutil verify "/Volumes/Image Volume/Install...High Sierra.app/Contents/SharedSupport/InstallESDDmg.pkg

and it comes back valid after a few minutes. One thing I have noticed is that there is another root copy of the Install high sierra.app in root (/.), which does not have the SharedSupport dir.

I would be truly appreciative of any advice. My only other device at the moment is an ancient chromebook. I've tried every available piece of advice I've found in the past few days, and I'm still stuck.

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I think you are facing a few issues here. I also don’t go to such extremes to install OS’s.

So lets first talk about getting the proper OS installer files. What you likely have are ones which have an expired certificate! Apple had set an expiration date to force people to newer OS versions. Well that sorta backfired as people wanted to still use their systems. Here’s a bit more explaining things: If you've got an old macOS install image, it will probably stop working today

So you have to get a fresh image file from Apples server’s. Review this Apple T/N How to get old versions of macOS. These files have a refreshed certificate so you won’t encounter the expired certificate issue.

As to going with high Sierra, frankly I don’t recommend it. Its the first version of Apples new APFS file system which still was buggy! And to add to it APFS is a very chatty dialog over what HFS+ (journaled file system) uses. Using APFS on a SATA based drive is the issue as SATA doesn’t offer as deep a buffer as PCIe offers.

The best macOS for your system is Sierra 10.12.x

After downloading it you’ll need to setup a bootable OS installer drive. I would recommend setting up a 32GB USB thumb drive to the task first formatting the drive the GUID and a journaled file system. Then follow this guide to prep it How to create a bootable macOS Sierra installer drive

With that done you should be able to boot up your iMac under it. Restart your system with the USB then drive plugged in press the Option (⌥) which will allow you to select USB drive as the boot drive (it might automatically start up under the USB drive)

Reference: Mac startup key combinations

I would recommend you completely reformat the drive and install a fresh OS. Unless there is something on it you want to safe then make a TimeMachine backup so you can then restore what you want later.

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Thanks for the input Dan! What you are recommending is largely what I had done before opening this question. The new change you recommend is to install Sierra instead of High Sierra, because of the SATA/APFS incompatibility. I didn't know about this until now, thanks for making me aware. You clearly know more about this than I do, but can you say anything about why old, SSD-free machines would be listed as officially compatible with High Sierra? Was it only for people who chose to upgrade to an SSD boot? Late 2009 iMac's had no SSD option at all, so it's odd (to me) why they are listed as HS compatible.

I will find someone with a Mac OS recent enough to get Sierra, and I'll create a new USB for that install and try this again. I'll provide an update here accordingly.

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Sometimes Apple makes a mis-step or fails to warn people when its best to stick with the old when the change leverages the new hardware. The file system is one of those. APFS needs PCIe/NVMe based drives to work effectively as the boot drive.

The best way to think this is like a foot bridge which goes across a river. It was designed to people to get across not a car or truck as much as we want to get them across its not able to.

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