


(be patient, the procedure of cloning does take some time. That way you can clone back, and get back your system if anything goes wrong. Use that to clone the internal drive with macOS to a spare hard drive.

There is an app called Carbon Copy Cloner (if I remember you can get a free trial for 14 days or something like that, enough to do your procedure) which allows to fully clone your hard drive to another one. There are (plenty of) Linux tools to do this, but I assume you may be more familiar with macOS. Since you say you are new to Linux, and because the stuff you want to do can go wrong if you make a mistake, I highly suggest making a full backup of your macOS system before anything. It's like pulling your own shoes to lift you up

The problem you are encountering is because you are trying to install on the same disk you are booted from. You normally also do not need to format the drive, just use Etcher and it will do the formatting. A 4GB flash drive is sufficient (maybe even 2GB is enough). You do not need a whole external hard drive to make a live USB. I am not much of a Linux techie so please make your reply easy to follow. I assume that after a correct installation I shall be able to boot the full MintOS by holding the "Option" key and shall be able to save all changes when I log out of each session. Please correct this from the partitioning menu", then I just quit the installation. I successfully complete all the steps including selecting my 500gb drive as the destination drive, then when I click on "Install" get a message saying " No root file system is defined. Now I want to permanently install Mint 19.1 to this same 500gb external hard drive because I want to save the changes I make after each session. This live USB loads perfectly by using the Option Key on my iMac. I made a live USB of Mint 19.1 using Etcher on a 500gb External Hard Drive with a format of MS-DOS FAT using Disk Utility to format on my mac running Mac OSX Yosemite. I am new to Linux Mint, am very anxious to make it another OS.
