disk0 doesn't show up in Disk Utility

[TitanTiger]

Let me see if I can explain this.

Last night something on Yahoo (I think a video trying to load) froze my computer up and I had to force power down using the power button on my iMac. I didn't realize at the time it was Yahoo's page that caused it and when Safari launched again it came back to all the tabs open before and caused it again, forcing another power down.

When I got back up and running and everything, I ran Disk Utility to repair permissions. But now instead of the disk0 root drive at the top that shows something like "HITACHI SATA 500GB HDT7210..." whatever (can't remember exactly) and then the partitions underneath that, it's showing my Yosemite partition as the top level drive, then the Yosemite partition and the iMac HD partition underneath. I can still boot into either partition and everything seems to be intact. But I cannot get this corrected.

All S.M.A.R.T. status stuff looks good. What is going on and how do I fix this?

See attached photo for what I'm talking about

 

[DeltaMac]

Reboot to your Recovery partition. (Restart, holding Command-R)
Run Disk Utility from the recovery menu screen.
Do you still see the same (29.35 GB) volume group, and it's almost completely filled?
Try the Repair Disk (different from Repair Permissions) on the drive, then on each separate partition under the drive.
Restart normally after that repair.

 

[TitanTiger]

Reboot to your Recovery partition. (Restart, holding Command-R)
Run Disk Utility from the recovery menu screen.
Do you still see the same (29.35 GB) volume group, and it's almost completely filled?
Try the Repair Disk (different from Repair Permissions) on the drive, then on each separate partition under the drive.
Restart normally after that repair.

Well, it didn't work. I actually had to run it from an external backup drive because it wouldn't run the repair on the current drive. But it went through and "repaired" the drive but didn't change anything even after reboot.

 

[DeltaMac]

I "think" you will need to revert the corestorage volume back to normal HFS volumes. Maybe some one else will chime in about that. I know the basics, but I also am not sure it will help in your case.
Review the man for the diskutil in your terminal. Look under the coreStorage section, then the "revert".
Or, might be simpler (if you have a good current backup) to erase that drive, then restore from your backup..

 

[TitanTiger]

I "think" you will need to revert the corestorage volume back to normal HFS volumes. Maybe some one else will chime in about that. I know the basics, but I also am not sure it will help in your case.
Review the man for the diskutil in your terminal. Look under the coreStorage section, then the "revert".
Or, might be simpler (if you have a good current backup) to erase that drive, then restore from your backup..

I do have a good current backup of both the Yosemite partition and the main iMac HD partition. I was hoping to not have to do that if there was a simpler way to get it right. Maybe someone will chime in with more on that revert command.

Everything I'm reading seems to be talking about using revert to change it from being an encrypted disk. Is the disk encryption perhaps part of the issue?

 

[DeltaMac]

Ah, OK.
If you have encryption turned on, turn that off, and try your disk utility again.
I don't use that myself, so I sometimes don't think about some of the issues that can turn up, particularly when you have issues that force you to turn off your Mac, for example.

After your hard drive is operating normally again, then you should be OK with encrypting again at that time.

 

[TitanTiger]

Ah, OK.
If you have encryption turned on, turn that off, and try your disk utility again.
I don't use that myself, so I sometimes don't think about some of the issues that can turn up, particularly when you have issues that force you to turn off your Mac, for example.

After your hard drive is operating normally again, then you should be OK with encrypting again at that time.

That did the trick. Turned off Filevault encryption, booted to Recovery and repaired the disk. After a reboot, the main disk shows up like it should.

Thanks so much for the help.