Help - boot partition missing after High Sierra update

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Level 1

96 points

Help - boot partition missing after High Sierra update

Hi -

I just updated my MacBook Pro 5,1 to High Sierra. The install went fine, and then I applied the 10.13.6 update from the App Store. My machine stopped booting and I now see the "No" symbol (circle with line through it) on boot and then boot to the recovery partition.

In Disk Utility, my boot drive has the recovery partition and unused space that is really my "Macintosh HD".

In terminal, 'diskutil list' says (I'm typing this in so it is a bit paraphrased):

/dev/disk0 (external, physical)

0: GUID_partition_scheme 512GB disk0

1: EFI EFI 209MB disk0s1

2: Apple_HFS RECOVERY 20GB disk0s2

3: Apple_Boot Recovery HD 650MB disk0s3

4: <GUID> 490GB disk0s4

So, disk0s4 is my boot partition "Macintosh HD". How do I recover this and get my system to boot again?

Thanks,

Ralph

Mac Pro, macOS High Sierra (10.13.6)

Posted on Aug 9, 2018 11:52 AM

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Answer 1

Kappy

Level 10

361,855 points

Aug 9, 2018 1:55 PM in response to rzazula

Prohibitory symbol

When you see a circle with a slash symbol instead of the Apple logo, it means your Mac couldn't find a valid System Folder to start up from.

If you're using your Mac at a school or business, it might be trying to start from the wrong version of macOS. Contact your IT department for more help.

If this is your personal Mac, try reinstalling macOS using macOS recovery.

Install El Capitan or Later from Scratch

If possible back up your files.

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

This will install the version of OS X you had installed.

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Answer 2

rzazula Author

Level 1

96 points

Aug 9, 2018 9:09 PM in response to rzazula

UPDATE 2 : system restored! I used the bootable USB stick to image a copy of High Sierra's "BaseSystem.dmg" to the RECOVERY partition.

One trick remained, the system still would not boot (gave me the circle-slash symbol again). I went into recovery mode again and selected "Macintosh HD" as the startup disk and then it booted.

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Answer 3

rzazula Author

Level 1

96 points

Aug 9, 2018 2:57 PM in response to Old Toad

It appears my recovery partition is El Capitan. So, the thought is that it won't recognize the new boot partition format...

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Answer 4

rzazula Author

Level 1

96 points

Aug 9, 2018 2:05 PM in response to Kappy

The point is that I don't want to erase the partition. It is a previously working High Sierra boot partition.

Something happened during / after the 10.13.6 update that rendered it non-bootable.

FYI - this is an NVRAM M.2 SSD that shows up as an "external" disk. It is on a PCI card inside of the computer.

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Answer 5

rzazula Author

Level 1

96 points

Aug 9, 2018 6:20 PM in response to Old Toad

This machine has a ton of customizations, drivers, etc. that would not be preserved with a full install.

Luckily, all my user data is on another volume, so I'm only working with the system files.

I'm building an externally bootable USB to see if I can find my drive - I think the boot loader is so out of date that it doesn't recognize the new filesystem in High Sierra...

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