Disk Utility will NOT resize partition in El Capitan

Delete partion 2, resize 1 and remake 2.

No, you can't restore an image that is smaller than the image.

You also can't resize p1 when p2 exists.

Then why do you need my help.

Goodnight.

I'm having the same problem. I want to enlarge my Time Machine backup partition and cannot resize it, even though I erased a big chunk of the HD. How did you "take" the drive to Yosemite? Or do I downgrade my iMac to Yosemite? (I went from OS X 10.7 to El Capitan without other issues....at first it wouldn't do TM backups because I got not enough available space message. Now TM seems to be working, can't recall what I did! I want to increase TM partition so I have plenty of space as I add photos etc. I have additional RAM to install so want to be sure I have a good backup first, of course.) Thanks in advance.

The answer to this problem is to run disk utility from a bootable USB drive. Here's how to create a bootable drive:

http://osxdaily.com/2015/09/30/create-os-x-el-capitan-boot-install-drive/

The error coming back saying that the disk can't be unmounted during the partitioning process is accurate, but misleading the journaling error is completely misleading.

I assume the problem is that the recovery partition is trying to unmount itself because it is on the same physical disk as the partition you are trying to resize. It worked the first try for me with the bootable USB.

I think the problem is more than trying to resize from the boot partition. I've been trying to resize my backup computer's boot partition to match the primary machine, to facilitate my backups with carbon copy cloner (the backup has a smaller total drive). Using the primary mac and backup in target disk mode, when I asked to resize the backup drive it couldn't do it unless I first deleted the non-boot partitions, and then the first attempt to resize the boot drive from 200 to 300 GB resulted in a 250 GB final partition. The second round--when I changed the backup computer non-boot-partition name (left it as default untitled) correctly resized all. That's pretty buggy when the partition names dictate whether the partition sizes result as entered or not!

Is this any help?

Disk Utility (El Capitan): Partition a physical disk

Didn't help me. The issue seems to be that El Capitan Disk Utility simply doesn't function as documented. Moving the size sliders and then hitting apply, results in no changes and no errors when I try it on a 4 GB Elite Pro USB drive. If I try to erase the whole disk and set up five partitions, I get errors such as "Mediakit reports partition (map) too small" Operation failed.

This works well on Yosemite, so I'm assuming it is due to bugs in the new Disk Utility on El Capitan.

This should assist with the above error.

http://superuser.com/questions/233531/how-can-i-resolve-the-error-mediakit-repor ts-partition-map-too-small

This really leaves a lot to be desired. I wanted to make one partition bigger and the other smaller. When I shrank the first partition, it created a new untitled partition, and wouldn't let me grow the other one. I ended up using diskutil mergepartitions.

While it is pretty dumb that it thinks journaling is disabled if a volume is unmounted, resizing with the volumes mounted seemed to work ok. Maybe a little more dangerous, if that was your concern.

We're at 10.11.3 now and this seems as broken as it ever was. I wish Apple would fix this, but I'm guessing we'll be waiting until the Fall, or whenever 10.12 is released. Perhaps there's some third-party software with this functionality? Preferably free.

Edit: Actually, what I really needed was a way to move a partition down so that the other one had room to grow. That might've not been possible in Yosemite either without using the merge, or wiping the drive and starting over.

Reducing the number of partitions is actually quite easy, maybe this little video will help. https://www.youtube.com/watch?v=32A7FlBst5g the author does a good job of showing you how to remove a partition.