Install OSX High Sierra on an older Mac using Terminal

Install OSX High Sierra on an older Mac using Terminal


Have you tried installing OSX on an older vintage machine recently? Well, I came across a unique problem when trying to upgrade my HDD to an SSD on my Vintage 2009 iMac. I thought I would share my experience and potential work around to get OSX high Sierra (the latest compatible OSX for my system) working on my iMac (2009).

Firstly after coming from a windows environment where you can grab a ISO and just create a bootable disk quite easily. However on a new Mac (I currently use the new M3 MacBook Pro) it is impossible to download High Sierra thought the mac store unless you have an eligible machine.

Apple provides a list of OSX download links here. However from high sierra onwards they only provide mac store links, this again means I can no longer download high sierra on my device.

I had an idea on how to get around this (so I thought)

It seemed quite a simple solution initially, and that I would download Sierra and then upgrade after a successful install. Again this proved fruitless as the ISO that I downloaded just had a .pkg file in the .dmg not a bootable usb drive!

It seemed I had no choice but to try and download the original installer package form mac store using the links they provide. The only problem is that my mac was too new and I can’t download the package direct to my MacBook. (you need to have an original machine running the OSX first)

The next step

I had read somewhere that the only way to get a copy of the original installer then use terminal to create a boot disk! But where was I going to get a copy of the OSX high Sierra installer.

I managed find a copy that someone had shared online (this is defo not recommended but I was frustrated after hours of getting nowhere), I was concerned about the download having a virus etc. But the website seemed legit and as this wasn't my main machine, I thought why not!

Here is the download link if anyone is interested. Once the package is downloaded it should look like this in your applications folder:

Below is the custom commands I then used in terminal to create the boot disk. The first step removes the signature error you receive when trying the run the command in step 2, so by doing the modification in step 1, it then in turn allows the installer to run in step 2.

Step 1

cd /Applications/Install\ macOS\ High\
codesign -s — -f createinstallmedia
createinstallmedia: replacing existing signature

Step 2

sudo /Applications/Install\ macOS\ High\ — volume /Volumes/MyVolume

The next step after this is to take your newly created boot disk and insert it into the mac you wish to install it on and boot into the installer. To do this hold the Option (⌥) or Alt key on start up to launch the Startup Manager, which allows you to choose other available start-up disks or volumes.

Unfortunately, I came across an issue after trying to install the OS. It stated the install was corrupted, but after doing some research I found out this was due to the install being too old and apple adds a signature to the OSX download which keeps it current, again another annoying step to work around!

My only hope at this point is to find a mac with Sierra installed and the navigate the mac store and download the version direct from the Apple Store.

At this point it has become so difficult I may just install Ubuntu just to use the machine, my only hope to get high sierra installed is just to get a recent download of the OSX installer!

For now I’ll keep looking for a solution and update the article if I know more!

For now… good luck and keep going!



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