Release the key when the screen displays your available boot drives.
This is a known issue when trying to install older macOS versions (including High Sierra) on modern systems or after Apple's signing certificates have expired. The solution is to to a point when the certificate was still valid:
The system will open the Software Update panel or App Store download queue. Once completed, the file Install macOS High Sierra.app will appear in your /Applications folder. Method B: Fetching via Terminal macos high sierra 10136 dmg install
This comprehensive guide covers everything you need to know about safely sourcing the DMG file, preparing your system, and completing the installation process. System Requirements for macOS High Sierra
To perform a clean installation or rescue a system, you must convert the DMG/App file into a bootable USB drive (minimum 16GB). Release the key when the screen displays your
Modifying system files or executing a clean install completely wipes your storage drive. Connect an external hard drive to your Mac. Open > Time Machine . Click Select Backup Disk and choose your external drive.
Select APFS if your Mac uses an SSD. Select Mac OS Extended (Journaled) if your Mac uses a mechanical Hard Drive (HDD) or a Fusion Drive. Scheme: GUID Partition Map Click Erase to wipe the drive. Once completed, the file Install macOS High Sierra
To perform a clean installation, you must convert the downloaded installer into a bootable USB drive using the macOS Terminal. Connect your 16GB+ USB flash drive to your Mac.
Open (found via Finder > Applications > Utilities).
Once you have your bootable USB ready, follow these steps to install macOS High Sierra 10.13.6:
If you encounter an error where the command is immediately killed, you may need to remove the code signature from the createinstallmedia tool using this command before retrying: