Can't create/adjust/delete a partition So I wanted to create a new partition to test the new El Capitan operating system. But I'm unable to create a new partition, the '+' sign is greyed out.

This is what I have currently configured for my drive:


Now I've googled this problem and found similar cases but they all mentioned that it's because the 'Revertible' setting was configured 'No'.

Now in my case this is configured 'Yes (no decryption required)' as shown below:

CoreStorage logical volume groups (1 found)
|
+-- Logical Volume Group 9EDF35D5-3B14-4F68-8A1A-98151AB82671
    =========================================================
    Name:         Mac
    Status:       Online
    Size:         179371204608 B (179.4 GB)
    Free Space:   18882560 B (18.9 MB)
    |
    +-&lt; Physical Volume 3DB04CA6-AF59-4FF4-9D01-E5D9C5418933
    |   ----------------------------------------------------
    |   Index:    0
    |   Disk:     disk0s2
    |   Status:   Online
    |   Size:     179371204608 B (179.4 GB)
    |
    +-&gt; Logical Volume Family 721050CD-09E2-4002-A065-8C724204B12C
        ----------------------------------------------------------
        Encryption Status:       Unlocked
        Encryption Type:         None
        Conversion Status:       NoConversion
        Conversion Direction:    -none-
        Has Encrypted Extents:   No
        Fully Secure:            No
        Passphrase Required:     No
        |
        +-&gt; Logical Volume C51A83AC-321D-4B5F-A5D7-7713F8B36874
            ---------------------------------------------------
            Disk:                  disk1
            Status:                Online
            Size (Total):          179000000512 B (179.0 GB)
            Conversion Progress:   -none-
            Revertible:            Yes (no decryption required)
            LV Name:               Mac
            Volume Name:           Mac
            Content Hint:          Apple_HFS
I was able to fix it by getting the UUID for my disk and then run the following command:

corestorage revert UUID


You can get the UUID for your corestorage disk by passing corestorage list and then you will get something like this Logical Volume C51A83AC-321D-4B5F-A5D7-7713F8B36874. The part behind 'Logical Volume' is your UUID.