You are making sure that the drive you identified in the first step is not already listed in here (this would be /dev/sda1 as my example above) as mounted. Next you will want to see what is already mounted. You can tell this due to the size of the partition.) ( sda being the hard drive, sda1 with 1 being the partition of the drive that is my OS. You will also want to look at the Device details for the drive to identify the partition on the drive that holds the OS. What you are looking for is /dev/sd* (* in this case, means any letter a-z. This will output a bunch of details about your hard drives. You can skip down to lsblk as I explain this below too. I like fdisk but you could also run lsblk as it may be easier for you. With Terminal open you are ready to begin. First open terminal by holding ctrl + alt then click t.
