I was upgrading my MacBook Air from Sierra to High Sierra, but the installation failed and the last line of log window was an error about
I restarted and then came across the blinking folder with question mark. So I tried recovery mode (Command + R). Disk Utility shows my Macintosh disk properly and there is no problem with it (I checked it with First Aid), but I cannot see any disks on Startup Disk window. what can I do to bring it there?
I have "Install High Sierra.app" on my external drive, can I use it somehow to install the OS?