Why can't I erase HD with Disk Utility?

Please post results of (using OSX Terminal).

diskutil cs delete C75EE6DF-CA8D-44F0-A15C-BF3BBB86DB84

diskutil list

diskutil cs list

Thanks,

Here is the read out from terminal:

Last login: Tue Oct 28 08:35:15 on console

Chris-Prendergasts-MacBook-Pro:~ chrisprendergast$ diskutil cs delete C75EE6DF-CA8D-44F0-A15C-BF3BBB86DB84

The Core Storage Logical Volume Group UUID is C75EE6DF-CA8D-44F0-A15C-BF3BBB86DB84

Started CoreStorage operation

Destroying Logical Volume Group

Erasing disk2s2

Initialized /dev/rdisk2s2 as a 465 GB case-insensitive HFS Plus volume with a 40960k journal

Mounting disk

Finished CoreStorage operation

Chris-Prendergasts-MacBook-Pro:~ chrisprendergast$ diskutil list

/dev/disk0

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *500.1 GB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_CoreStorage 499.2 GB disk0s2

3: Apple_Boot Recovery HD 650.0 MB disk0s3

/dev/disk1

#: TYPE NAME SIZE IDENTIFIER

0: Apple_HFS Untitled *498.9 GB disk1

Logical Volume on disk0s2

4306F405-E4CD-46A4-A31E-7D7BC1199F32

Unencrypted

/dev/disk2

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *500.1 GB disk2

1: EFI EFI 209.7 MB disk2s1

2: Apple_HFS Untitled 499.1 GB disk2s2

Chris-Prendergasts-MacBook-Pro:~ chrisprendergast$ diskutil cs list

I think it's done it!

I've just formatted the SSD...

Going to do a back up in time machine now on a separate drive, put the SSD into this mac and hopefully restore...

Wish me luck...

You should now be able to restore your TM backup to /dev/disk2. Select this disk as the destination for your TM restore by selecting "Show Disks" during restore.

I had this Exact problem while trying to do bootcamp on a brand new macbook,

My computer was only booting in Recovery mode and wouldn't show "Macintosh HD" when I tried to recover from Time Machine.

I did what Loner T said to do:

diskutil cs delete C75EE6DF-CA8D-44F0-A15C-BF3BBB86DB84

diskutil list

diskutil cs list

Once I did this replacing that HD UUID with my own, I was able to see the drive again and recovered the Mac using Time Machine.

Thanks!

I would like to understand a bit more how this all works. I replaced the HD in my MacBook with an SSD. To do that I did the following:

- installed the SSD in an external USB drive enclosure

- installed Yosemite 10.10.2 from scratch on that external SSD

- restored all files from my TM backup

Only once I was satisfied that the SSD booted fine and was OK did I remove the internal HD and replace it with the SSD. I then mounted the old internal HD into the external USB enclosure.

Now I want to use that external drive as a regular drive, and I would like to erase it. But I observe the following:

1) When I plug in the external HD, it does not appear in the "Devices" section of the Finder. But the drive mounts fine (it is in /Volumes, on the desktop and also as a "Removable Volume" and I can access all files.

2) Exactly like described above, when I look at the drives in Disk Util, I see that the external drive only has the "First Aid" and "Partition" choices. No "Erase", "Raid" or "Restore" choices. And the drive appears as a "Logical Volume Group". On the other hand my internal SSD I boot from appears as a regular drive. The partition appears as a "Logical Partition". I can erase that partition, but I cannot erase the drive proper or repartition it.

Here is the output of "diskutil list"

$ diskutil list

/dev/disk0

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *500.1 GB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_HFS Macintosh SSD 499.2 GB disk0s2

3: Apple_Boot Recovery HD 650.0 MB disk0s3

/dev/disk2

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *750.2 GB disk2

1: EFI EFI 209.7 MB disk2s1

2: Apple_CoreStorage 749.3 GB disk2s2

3: Apple_Boot Recovery HD 650.0 MB disk2s3

/dev/disk3

#: TYPE NAME SIZE IDENTIFIER

0: Apple_HFS External *748.9 GB disk3

Logical Volume on disk2s2

7EE41451-8421-44AE-A249-343E1A3CCB25

Unencrypted

It shows that the old HD used Core Storage, and that is why I cannot use it as I expect, but using the diskutil command line I expect to be able to clean it out just like you explained. "diskutil cs list" shows:

$ diskutil cs list

CoreStorage logical volume groups (1 found)

|

+-- Logical Volume Group B0341F77-1A3C-42EE-9FE2-209CE49CED8A

=========================================================

Name: Macintosh HD

Status: Online

Size: 749296615424 B (749.3 GB)

Free Space: 18939904 B (18.9 MB)

|

+-< Physical Volume EA971DCF-EFB3-40F2-8B8A-18507B794476

| ----------------------------------------------------

| Index: 0

| Disk: disk2s2

| Status: Online

| Size: 749296615424 B (749.3 GB)

|

+-> Logical Volume Family 602297D8-5616-41AC-A639-2BA43C50DB4C

----------------------------------------------------------

Encryption Status: Unlocked

Encryption Type: None

Conversion Status: NoConversion

Conversion Direction: -none-

Has Encrypted Extents: No

Fully Secure: No

Passphrase Required: No

|

+-> Logical Volume 7EE41451-8421-44AE-A249-343E1A3CCB25

---------------------------------------------------

Disk: disk3

Status: Online

Size (Total): 748925353984 B (748.9 GB)

Conversion Progress: -none-

Revertible: Yes (no decryption required)

LV Name: External

Volume Name: External

Content Hint: Apple_HFS

The thing I am not clear with is:

* why was the HD configured that way ? My MacBook was pre-installed with Lion when I got it, and I upgraded it regularly through the later versions all the way to Yosemite.

* why did the clean install on the SSD not build the same structure using Core Storage ? I thought that this was done automatically during the upgrade to Yosemite ? But not during a clean install ?

Thanks for any clarifications.

It would well pay to open your own thread on this. Not only has this post been marked as solved, therefore limiting the traffic here, but it is also over a year old and had nothing to do with Yosemite and SSDs. You will receive more attention in a new post in the appropriate forum.

Cheers

Pete

THANKYOU!!!

Thank you, Loner! I too had everything greyed out. Once I correctly made a bootable USB drive, I was able to reload my other three Macbooks but I somehow screwed up one (I think maybe because I formatted it for MacOS but not journaled). Couldn't erase/reformat it to save my life until I performed the "internet" recovery option. Now I'm back up and running! YOU DA MAN!

I came across this post, because I was also looking for solution to my problem which is similar. I was having a problem with my macbook pro, I decided to do a time machine backup on external drive and reinstall from it. When I tried to restore, I got a message unable to erase. I tried to format, but I could not because everything was greyed out. I checked the info. for HD, it shows read only.

I have worked on windows many times before, this is first time I am working on macbook. Please help.

Thank you,