Fix partition map with empty partition

CuriousGoose wrote:

HWTech wrote:

What do you mean by this? Is this a full macOS bootable drive? Or just a macOS USB installer?

Yes. Creating it wasn't so easy. I needed to download a Mojave installer from archive.org through my Windows PC and use TransMac to make it work. I installed the OS on the same flash, so it's now a bootable, and very slow macOS system.

While booting a full macOS from a USB stick is technically possible, it will perform extremely slow. If you want to recover your data, then invest in a real external USB3 SSD for the full macOS external boot drive. Besides, you have to store the recovered files somewhere anyway. I gave up on using a USB stick to boot a full macOS installation decades ago. Even using a slow Hard Drive is so much better although it can still be painful.

The macOS command line utility only offers the option to transfer the backup partition table to replace the main partition table. I'm not aware of any macOS utilities or third party apps which can view or compare them.

This sounds risky. Especially since First Aid told me that the partition map is corrupted. I wasn't able to even try the repair using First Aid because I got an error after waiting for over 2 hours.

It is only risky if the backup partition table is not correct for the current layout (rare, but I don't know what may have been done to this drive). And if the drive does indeed have a hardware issue, then writing anything to the drive is risky.

Can you see all of the health attributes of the drive with Disk Drill? This also sounds like an old iMac or Mac Mini with a Hard Drive, or a MacBook Pro 13" (mid-2012) non-Retina model which is using a Hard Drive.

I haven't booted into the macOS in some days. For one, it takes around 1 hour or more to boot into it. For two, I wasn't able to get anywhere with DiskDrill or SuperDuper!, so I had no reason to go there.

Without knowing the actual issues with the internal drive, it makes it impossible to make any suggestions.

Using a super slow USB stick is probably also contributing to the problem.

If you want to recover the data, then you will need to spend money on items to make it happen, or spend it on a professional data recovery service.

It's a Samsung SSD inside my MacBook Pro (Early 2015). The model is: A1502 EMC 2835. The internal SSD is Samsung S4LN058A01 8030.

Since you are booting macOS 10.14 Mojave, then it means this is still an Apple OEM SSD using a rebranded Samsung SSD.

Right now, I am exploring OpenSuperClone. I feel like it can get the job done, I just need someone to tell me which settings to use for my case.. and it's not easy finding someone who has experience with OSC.

I never heard of this before. From the brief description I read, it can be used to create a raw image of the drive since it mentions working like "ddrescue". At best, you will need to make sure you select an option where you can resume an in process image if it is interrupted....otherwise forget it. I have no idea how the virtual recreation part works.

You will need to contact the utility/app developer, or find a forum where people help others with OpenSuperClone. If I've never heard of it, then no one else on this forum is likely to know anything about it much less have any first hand experience with it.

FYI, this type of app would be able to recover data from a failing Hard Drive, but I don't hold out much hope of it being able to image the entire SSD if that SSD does have a hardware failure like I suspect from what you've described in this thread. SSDs fail in completely different ways than Hard Drives.

Anyone who uses an SSD must make sure to have frequent & regular backups because an SSD can fail suddenly without any warning signs. Even with warning signs, it may still be impossible to recover data from a failing SSD. Hoping won't make it any different. Sometimes you may have luck on your side, but most times there is no possibility of recovering data.

99% of SSD failures which I've personally seen while supporting my organization's computers are due to SSDs which fail suddenly (some may give a little warning, but people ignore the signs). The only other pure SSD failures I've seen was only after PBs of data had been written to the SSD and worn out the SSD.

Edit: Forget to mention I would like to see the health report for the internal SSD. Use DriveDx (free trial period) and post the complete text report here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar. Don't post any reports from Disk Drill since the DriveDx includes more information in its health report and in a layout which makes it easy for me to read & interpret the report.

Are you trying to recover data, or just trying to fix the system without erasing & reinstalling it?

It is never a good idea to make any modifications to a drive from which you want to recover data. Once those modifications are made, it may make any data recovery more difficult or even impossible. Such experiments should only be done if you are willing to lose the data or are just interested in "fixing" macOS without having to perform a clean install.

The best thing to do is install macOS to an external USB3 SSD & boot from that external SSD. With a full macOS you can try using the Finder to access the data on the internal SSD if it is able to mount. Otherwise, you can use a data recovery app to access the data....these apps generally can recover data even if the volume won't mount. However, if you must use a thorough or deep scan with those data recovery apps, then you may as well give up since you will be given millions of files with no names and no folder structures. 70% of them will be useless temp, cache, and system files, but you have no way of knowing what they are until you open each & every one of them (you will be given a file type, but that is it.....document, image, etc.).

FYI, people should always have frequent and regular backups of their computer and all external media (including the cloud) which contains important & unique data. There are a lot more new ways to permanently lose access to the data stored on the internal SSD of the recent Macs due to all of the hardware, software, and security changes.

Edit: There is a backup partition table located on the drive. There is a Terminal command line utility that can attempt to replace the main partition with the backup copy. As long as that backup partition table matches the main table (but without the errors), then it may work. This is the least risky modification that can be made, but it does still entail risk. Can you take that risk?

You can also contact a professional data recovery service if the data is really important & critical if you cannot risk the data.

CuriousGoose wrote:

1. I'm trying to get the data from my SSD in case the repair/fixing goes south.

So no backups. This is lesson many people must learn the hard way.

I have a bootable macOS flash.

What do you mean by this? Is this a full macOS bootable drive? Or just a macOS USB installer?

This is very important because the former offers us many more options for assessing the drive.

I have no external SSDs, unfortunately. Finder was unable to see the data on the internal SSD. So far, only two methods allowed me to see the files and folders on my internal SSD (Macintosh HD):

"cd" command in Terminal (no longer works since Macintosh HD isn't listed under ls/Volumes)

2. Virtual disk mode in OpenSuperClone

So the "Macintosh HD" volume cannot be mounted.

while DiskDrill would only get to 4.64GB before my internal SSD ejected.

This sounds like a hardware issue with that internal drive.

This is the first time I am hearing about the backup partition table. Can you tell me more about this? How can I check whether the backup matches the main table?

The macOS command line utility only offers the option to transfer the backup partition table to replace the main partition table. I'm not aware of any macOS utilities or third party apps which can view or compare them.

DiskDrill did show that there are 2 bad sectors, but I don't know. That's why I haven't tried this method yet, it carries a certain risk with it

That was important information to know for assisting you. It further confirms there is a hardware issue with the drive. When a hardware issue exists with a drive, you must proceed very carefully since you are likely to make the failure worse where even an expensive professional data recovery service will be unable to recover any data.

Can you see all of the health attributes of the drive with Disk Drill? This also sounds like an old iMac or Mac Mini with a Hard Drive, or a MacBook Pro 13" (mid-2012) non-Retina model which is using a Hard Drive.

What is the exact model of this Mac and version of macOS on it? Also, what file system is being used on this broken drive? You can get the exact model of the Mac by clicking the Apple menu and selecting "About This Mac" assuming you can boot into the full macOS. Otherwise you can enter the system serial number on the check coverage page here (please don't post the serial number on the forum since it is considered personal information):

View Coverage - AppleCare & Warranty

Simply adding a partition will be a non destructive method for 99%. But if your disk has physical sector failure, it can be destructive. But if the mac is not booting now, what do you have to lose i would say

CuriousGoose wrote:

I have the same problem

I have had the same issue for a few months but I have decided to ignore it as a cosmetic issue and just do extra backups.

So Disk Utility reports this when Command-R booted to local Recovery:

"Problems were found with the partition map which might prevent booting

Disk Utility error "Couldn't mount disk. : (-69842)

Operation failed..."

BUT if I Option-Command-R boot to Internet Recovery, THEN there is no such error via its Disk Utility. See also:

Disk Utility error "Couldn't mount disk (… - Apple Community

First Aid on Physical Disk Fails ?!! - Apple Community