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Installing a Newer OS on a Partitioned Internal Drive?




Hello folks,


My 2010 iMac has a partitioned HD. On one partition I’m running 10.6.8 in order to support and old version of Pro Tools. On the other drive I was running High Sierra in order to accommodate Logic Pro X and to use newer software. I had to erase the latter partition a while ago but now want to revert back to the way it was. The only problem is, I forgot how I did it! 


I have different versions of different OS’s that I’ve downloaded but can’t seem to figure out how to install any of them. I’d prefer to go as high as Mojave but would be fine with High Sierra. 


Many thanks in advance!

iMac 27″, macOS 10.13

Posted on Jul 22, 2020 2:01 AM

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Question marked as Top-ranking reply

Posted on Jul 22, 2020 2:30 AM

First of all your 2010 mac cannot upgrade to Mojave, Mojave requires your iMac to be from 2012 or later.

So High Sierra it is.

If you have the installer apps for El Capitan and High Sierra you may find that they will not install as in October 2019 the certificates for several OS's expired. One way to get around that is to go into System Preferences> Date & Time

and reset the date back to a time before October 2019.

As you are on Snow Leopard at the moment you would need to install El Capitan first and then install High Sierra.

When the installer starts follow the prompts, at one point you will be asked to select a disk to install to, select the

partition/ disk you want to install to, not the Snow Leopard disk.


There are revised versions of El Capitan and High Sierra available for download with updated certification.


How to upgrade to OS X El Capitan – Apple Support

Go to Section 4 and click on Download OS X El Capitan

this will download InstallMacOSX.dmg to your Downloads folder.

Once that is done you need to unpackaged it, if you want instructions

on how to do that ask here, it can be quite confusing.


For High Sierra, open your Safari browser, Firefox will not work.

How to upgrade to macOS High Sierra - Apple Support

Go to Section 4 and click Get macOS High Sierra,

this will redirect you to the App Store High Sierra download page,

it should say Get ir Download.

This will download Install macOs.app to your Applications folder.

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3 replies
Question marked as Top-ranking reply

Jul 22, 2020 2:30 AM in response to P Willis

First of all your 2010 mac cannot upgrade to Mojave, Mojave requires your iMac to be from 2012 or later.

So High Sierra it is.

If you have the installer apps for El Capitan and High Sierra you may find that they will not install as in October 2019 the certificates for several OS's expired. One way to get around that is to go into System Preferences> Date & Time

and reset the date back to a time before October 2019.

As you are on Snow Leopard at the moment you would need to install El Capitan first and then install High Sierra.

When the installer starts follow the prompts, at one point you will be asked to select a disk to install to, select the

partition/ disk you want to install to, not the Snow Leopard disk.


There are revised versions of El Capitan and High Sierra available for download with updated certification.


How to upgrade to OS X El Capitan – Apple Support

Go to Section 4 and click on Download OS X El Capitan

this will download InstallMacOSX.dmg to your Downloads folder.

Once that is done you need to unpackaged it, if you want instructions

on how to do that ask here, it can be quite confusing.


For High Sierra, open your Safari browser, Firefox will not work.

How to upgrade to macOS High Sierra - Apple Support

Go to Section 4 and click Get macOS High Sierra,

this will redirect you to the App Store High Sierra download page,

it should say Get ir Download.

This will download Install macOs.app to your Applications folder.

Jul 22, 2020 2:53 AM in response to Eau Rouge

Dear Eau Rouge,


Many thanks! I forgot about the “time/date” trick.


I'm currently in the mode of reinstalling from Recovery Mode. (Restart, hold “Option” key and Install High Sierra on the partitioned drive.) So far, it seems to be working. Install note: The iMac must have an Ethernet connection as WiFi is not available. I forgot about that trick too. :)


If this method fails, I’ll definitely be following your advice, word for word.


Thanks so much for taking the time to provide me with your process!!! Bookmarked!


😃

Installing a Newer OS on a Partitioned Internal Drive?

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