Can you only partition a hard drive once? I am trying to create two partitions on my fairly old macbook air (2015 macbook air running Yosemite 10.10.5) My goal is to be able to dual boot ubuntu and from what I've seen i need to partition part of the drive for ubuntu and then create another partition that is slightly larger than my ram. I assume I should be trying to change partition layout but its greyed out.
Here is the diskutil for @Jean_JD
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *251.0 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage                         169.5 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data UBUNTU                  80.6 GB    disk0s4
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS Untitled               *169.1 GB   disk1
                                 Logical Volume on disk0s2
                                 232B9688-C0ED-4C8C-911D-E64019CA8B1F
                                 Unencrypted

Ive also tried partitioning untitled Mac os extended drive but I can only partition it once. Thank you for the help though everyone, I think I making a second partition for swap isn't needed for Ubuntu.
From what you have presented in your question, you are finished using the Disk Utility. When you install Ubuntu, you can use the tools provided by the Ubuntu installer to finish partitioning the drive. You can used these tools to do the following.

Delete the existing MS-DOS (FAT) formatted partition labeled UBUNTU.
Create a new partition for Ubuntu. You should give this the mount point /. If necessary, save some free space for the swap partition.
Create a new partition the desired size of the swap space. With the current releases of Ubuntu the creation of this partition is optional.


Note: Ubuntu will use the hidden EFI partition created when OS X was installed. This EFI does not appear in the image you posted. However, this EFI partition will appear in the Ubuntu installer when you change the partitioning. You can use the OS X command diskutil list to see all partitions including the hidden ones.