My MacBook Pro died during an update and now won't log on

Follow the above procedure. The volume is unmounted already which is OK. You can still select it. If you cannot proceed per the above, then you will need to erase the drive but cannot backup.

Install El Capitan or Sierra from Scratch

1. Restart the computer. Immediately after the chime hold down the CommandandRkeys until the Apple logo appears. When the Utility Menu appears:
2. Select Disk Utility from the Utility Menu and click on Continue button.
3. When Disk Utility loads select the volume (indented entry, usually Macintosh HD) from the Device list.
4. Click on the Erase icon in Disk Utility's main window. A panel will drop down.
5. Set the Format type to Mac OS Extended (Journaled.)
6. Click on the Apply button, then wait for the Done button to activate and click on it.
7. Quit Disk Utility and return to the Utility Menu.
8. Select Reinstall OS X and click on the Continue button.

Reinstall El Capitan or Sierra Without Erasing Drive

Please be sure you back up if you can.

1. Restart the computer. Immediately after the chime hold down the Command and R keys until the Utility Menu appears.
2. Select Disk Utility and click on the Continue button.
3. Select the indented (usually, Macintosh HD) volume entry from the side list.
4. Click on the First Aid icon in the toolbar. Wait until the Done button activates, then click on it.
5. If First Aid fails or returns errors let us know what they are. If it reports the drive cannot be repaired or returns a failed I/O error, that usually means the drive should be replaced. Do not proceed.
6. Quit Disk Utility and return to the Utility Menu.
7. Select Install OS X and click on the Continue button.

Also, see this User Tip: Basic Steps for Upgrading OS X.

Hello,

I am having the same issue. However, my format of Mac doesn’t have the one you mentioned on the erase fix. The only options are APFS

APFS encrypted

APFS case-sensitive

APFS case-sensitive, encrypted

Which one do I choose?

Choose APFS. You must be running macOS High Sierra (10.13.x). It introduces a new Mac file system.

Howard

HW, that looks like a kernel panic. The Mac should normally startup properly the next time.

It's a long shot but try zapping parameter RAM at startup. When you turn your Mac on, hold down the keys Command-option-P-R. Keep holding them until your Mac reboots at least 2 more times. This may not accomplish anything.

I would recommend that you make an appointment to take your Mac to the Apple store. It is quite likely that key operating system files are damaged/corrupted because your Mac died while they were being updated. Hopefully your data was backed up; preferably using Time Machine.

Howard