Upgrade Failure
Was in the middle of this OS upgrade and lost power and internet connection. Now machine is stuck and won't boot up. Tried powering down and starting up again, but not working. How do I stop the update or restart from beginning?
Was in the middle of this OS upgrade and lost power and internet connection. Now machine is stuck and won't boot up. Tried powering down and starting up again, but not working. How do I stop the update or restart from beginning?
Try holding the Option key just after the startup chime (or powering on the Mac if it is newer and doesn't chime). See if there is an "Installer" option which may let the installer continue or if there is a "Macintosh HD" option try it to boot normally.
You don't mention what version of macOS was previously installed or which version you are installing. You can try booting into Recovery Mode to begin reinstalling macOS again (either with the original OS or the one you were trying to install -- which one you get may depend on how far the progress got).
If you have another compatible Mac you can also try creating a bootable macOS USB installer:
Try holding the Option key just after the startup chime (or powering on the Mac if it is newer and doesn't chime). See if there is an "Installer" option which may let the installer continue or if there is a "Macintosh HD" option try it to boot normally.
You don't mention what version of macOS was previously installed or which version you are installing. You can try booting into Recovery Mode to begin reinstalling macOS again (either with the original OS or the one you were trying to install -- which one you get may depend on how far the progress got).
If you have another compatible Mac you can also try creating a bootable macOS USB installer:
Upgrade Failure