High Sierra installation failed and I can’t restart my computer

Holding the Option key at the startup chime, will show you the boot options available, if they are not showing in the Startup Preferences. Else, start into the Recovery Partition (Cmd+R) and in Disk Utility make sure the volume is mounted.

Sorry about your main issue but sounds like we need to wait for a fix.

When you get the dialog box with the reset prompt, click anywhere in that box except for restart. Once you do that, the menu bar up top becomes available. Click the Apple at the far left and select startup disk, select your old startup disk and it should start your computer with the original OS.

I have tried all the options below without any success. What I found worked was when you get the splash screen stating that the OS cannot be installed, you need to reconnect to Wifi. in the far right top corner you will see the Wifi symbol. Double click this and select your network. You'll need to re-enter your Wifi password. Once you have done this, restart your mac and the iOS installs correctly. Its a shame that this update booted people from their Wifi networks because it installs correctly once online. If all else fails, try that. It worked for me.

similar problem did the upgrade then it would not mount the disk...tried a number of things...

finally i did a time capsule restore and it worked...it went back to the last version of the OS then re-did the upgrade and it worked...

(it wipes the disk then does the restore so the upgrade to the new file system does not matter...)

i posted the details earlier today

I had the same problem today. Gave up and rebooted from clone. Now recloning internal drive.

Had to run First Aid on internal drive for the reclone using Smart Update to work, so I wonder if I should have run First Aid before trying the installation (a good practice anyway)!

I had a similar failure. In my case the error was com.apple.diskmanagement error 0. Each reboot just went right back to the installer - no way to just boot back into Sierra. Installing from recovery mode didn't work either, same error.

After a long day of frustration, I gave up and reinstalled Sierra from a bootable USB stick. Unfortunately, in its great wisdom Apple seems to have made Sierra impossible to find. Luckily I was able to find a friend who still had the installer.

My system is a late 2012 Mac Mini. I would like to upgrade to High Sierra, but won't try again until I have some time on my hands to repeat the Sierra installation (if needed).

By selecting recovery 10.13.1 HD and not the Mac OS installer after restarting with alt option key used . Will this Erase my drive there for losing content. Hope you can help this suck . First time I have ever had a problem with Apple or OS in over 15yrs

I did. The only problem is finding a copy of Sierra, since Apple has hidden it. You will probably need to put it on a bootable USB stick.

Nothing to do with the spelling of "Installatio" is it?

Can you reinstall Sierra over a failed High Sierra install without losing any of your data?

This worked. Thanks for the help.