Following the example of PenDriveLinux we want to be able to boot from any one of a number of ISO files on a USB stick. We have one immediate problem in that one of the ISOs we want to use, a CentOS 7 DVD image, is 4.2GB which is larger than a FAT32 partition can handle. A second driver is that we want to use a UEFI boot.

We're using GRUB2 and starting with a CentOS 7.x system already running. This is a complication because GRUB2 is now documented as GRUB with GRUB v1 denoted as Legacy GRUB. On top of which examples refer to commands such as grub-install which exist in CentOS 7.x as grub2-install.

We're not trying to support (legacy) BIOS boots.