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High Sierra reinstall issues

Hi, I have a late 2017 21” iMac, 8GB of ram, running High Sierra. I have no recovery partition and startup switches do not work.


I have a copy of the High Sierra installer and have the command line input necessary to make a USB drive installable.


My questions, is there a way to specify a boot device without the Startup Manager? How can I create a Recovery Partition and, with a constant external backup, do I need to?


Thanks in advance for your advice.

Posted on Dec 16, 2020 1:29 PM

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5 replies

Dec 17, 2020 2:59 AM in response to StratDude

How Old is the dmg of High Sierra? If from years ago, the Certificate may have expired. Thus will kick out and error. If so, this link will give a newer version. Once the USB Installer is done, Option Boot at Startup will bring the Boot Manager and choose the Installer - Install High Sierra or can Wipe the Drive with Disk Utilities and Clean install. Before doing any of this, due diligence - have a Time Machine Backup before proceeding and if possible two separate Bootable Clones - Insurance.


That said, 2017 iMac an go all the way to Big Sur but here Empty Space Requirements are vey important as well as No 32 Bit apps for extensions are supported plus compatible Apps come into play

High Sierra reinstall issues

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