Can't delete a partition with Yosemite after El Capitan installation

[twetti]

Hello. I've two partitions on my iMac HDD. On the 1-st partition I've OS X Yosemite installed a year ago. On the 2-nd partition I've installed OS X El Capitan. I want to remove 1-st partition with Yosemite and resize 2-nd partition with El Capitan. But I can't delete 1-st partition with Yosemite. The “−“ button is gray and disabled. Why? How can I delete the partition?

 

[randomgeeza]

Hello. I've two partitions on my iMac HDD. On the 1-st partition I've OS X Yosemite installed a year ago. On the 2-nd partition I've installed OS X El Capitan. I want to remove 1-st partition with Yosemite and resize 2-nd partition with El Capitan. But I can't delete 1-st partition with Yosemite. The “−“ button is gray and disabled. Why? How can I delete the partition?
View attachment 589859 View attachment 589860

I may be wrong, and if I am, someone else may well correct me. However... I as understand it, the 1st partiton is the primary partition and as a result it cannot be deleted.

The way I would attack this issue is, CCC the partition you want to keep. Put that to one side on an external drive. Completely erase the drive so that it is then one partition and CCC the already copied preferred partition back.

Once complete, reset the SMC and PRAM and you should be good to go.

 

[twetti]

Thanks, randomgeeza, but I don't want to use CCC and I don't have an external drive. Maybe there is a better solution.

 

[chrfr]

Thanks, randomgeeza, but I don't want to use CCC and I don't have an external drive. Maybe there is a better solution.

Randomgeeza is correct. You can't delete the first partition.

 

[twetti]

One year ago, I installed OS X Yosemite, then I removed a first partition with OS X Maverics without any problems. Why I can't make the same actions with El Capitan?
Sorry for my English.

 

[CoastalOR]

Thanks, randomgeeza, but I don't want to use CCC and I don't have an external drive. Maybe there is a better solution.

Boot to the El Capitan partition, clone it to the Yosemite partition (I know you do not want to use CCC), restart to the new El Capitan partition (former Yosemite), and use Disk Utility to resize/remove the old El Capitan partition. This method would get you around the no external drive and CCC does have a free 30 day trial that would let you perform this task.
or
Install El Capitan to the Yosemite partition and use Disk Utility to resize/remove the old El Capitan partition.
or
Wait for a possible modification to El Capitan Disk Utility that might allow you to remove the current Yosemite partition.

 

[Weaselboy]

One year ago, I installed OS X Yosemite, then I removed a first partition with OS X Maverics without any problems. Why I can't make the same actions with El Capitan?
Sorry for my English.

This is not new with El Capitan. Even with Mavericks and Yosemite you could not do remove the first of two partitions. You must have done something else last time.

I have an idea that is a variation of what CoastalOR suggested. First backup everything just to be safe.

Now command-r boot to El Capitan recovery. Then start Disk Utility and resize the El Capitan volume to 230GB. This is necessary because Disk Util cannot clone a larger volume to a smaller (at least pre-El Capitan anyway).

Then select the Yosemite volume and erase it to Mac OS Extended format.

Once that is done select the top Yosemite volume and hit shift-command-r (all three keys at once). That will bring up a window similar to this.

Select the El Capitan volume in the dropdown here then click restore. That should clone the El Capitan volume to the Yosemite volume. Then remove the old El Capitan volume at the bottom and resize the new El Capitan volume to fill the disk. Reboot when done. That should work.

I'm fumbling around a little here because I have not tested a restore like this in El Capitan... but this should do the trick.

 

[twetti]

Thanks to all!