I've run into some issues trying to upgrade this older Mac from Lion. I know that I have to go through an intermediate OS before installing High Sierra. When I try to log in to any Apple site via Safari from that machine I get the "safari cannot obtain a secure connection" error. This also happens if I try to get into the app store. The next thing I tried was downloading an OS on my newer Mac. I tried this with both Yosemite and El Capitan. Download, copy to thumb drive, move drive to old Mac, copy to old Mac desktop, run the installer. The installer runs, but tells me it will take 7mb of space. Yes, you read that correctly, 7mb. I tried this with two different OSes. It runs, but does nothing, I'm still left with 10.7.5. I'm stymied as to what to do next. Any ideas would be greatly appreciated. Thanks.
You could probably do the update without going through previous versions. Try using Terminal (/Applications/Utilities/Terminal.app) to download the installer. Launch Terminal and enter this command:
softwareupdate --list-full-installers
Remember that you need to run this from your MBP, not from another Mac. You will be presented with a list of installer versions applicable to your Mac. You are looking for macOS 10.13.6 (17G65), the maximum that your MBP can run. Make sure that version 10.13.6 is on the list. Then enter the following command:
sudo softwareupdate --fetch-full-installer --full-installer-version 10.13.6
assuming that “10.13.6” is on the previous list. Press return, enter your admin password, and the download should start. If it finished successfully, you should see the installer file. I believe the High Sierra file is simply named “InstallOS.dmg.” If so, you will need to launch it in order to mount the actual file. Sorry I can test it here because I’m running on a Mac Studio M4 Max. Anyway, before mounting the .dmg file, you should make a copy to another location for future use. Then reboot into Safe Mode, mount the disk image, and proceed with the installation. I haven’t had to deal with High Sierra in a while, so I cannot test it here myself. Good luck. Remember, if the first try fails, you can give it another try, following the above instructions.
