it is not really the question: you only start so the iso from grub.
Williejordan will proceed differently (perhaps he has no iso any more or other reason):
he will copy the 3 or more files needing by grub to start each Linux (linux itself, initrd, and the external files used in initrd to directly start from then without to have to unpack the iso
on the PC from my dad did all stay as it was as he did dead. I did have a own part of it, and I did never change it. The first DebianDog out 2013..2014 unchanged was and is yet installed. It was my lovely OS, the best of all the time and I continue to use it frequently as the PC of my sport room (one reason is to remember to my dad, of course. but also because of the better old version of some software as we can install today in the new linux'es all (video player where you can change easily the speed of view and/or sound , where you can see and find with max. precision the point where a sport movement begins and look with max. details! I don't know if it's continue to be possible in the new video player versions - the names are the same, but the performances are killed .
I will upload a view on that old DebianDog, that best Linux on my numerous PC's, showing the menu (especially the Debian Menu within the general Menu: in new version, no application (or only a few one) is correctly connected any more (poor modern Linux!)... And you can see the grub text part for that first DebianDog (text probably build a that time by Deepin, the first one if I right remember of the new Deepin generation and the last Deepin 32 bit). Deepin cames later on the PC as my father was already dead and did (re)install the already present DebianDog installation perfectly after I did erase Windows from PC (I did renounce to have Windows more than 10 y. along; but I did one today again because of Linux itself: no all drivers can really work easily in modern Linux, for ex. my Printer HP Color Laser 150a, a best color laser, very cheap and makes beauty full outprints of color photos. In Windows, you have nothing to install: it works immediately as it is recognized by Windows and, at the other side, in Linux the installation of this printer is terror pure!
I find it was a fine frugal installation (and the old grub installer used by Deepin 32 was able to manage the installation itself! I have not made myself this complicated installations text!!!
Why did I abandone the use of DebianDog, that perfect Linux out 2013..2014?
Because of the Debian use of, obligatorish, one unique name, «live» for the installations directory. It did force me to often erase the content of that directory and replace it with an other one to continue to play with new versions as old Puppy users are accoustumed to do, with lose of software if somewhat was wrong, or to reinstall / actualize grub (enter in a Linux that you need at that time absolutely no use, as above Deepin 32 bit, only to actualize grub, because DebianDog was not able to do that himself...). I did not support any more those restrictions...