[CentOS] USB ISO for CentOS 8

[Jerry Geis]

>Then generate the .iso:

># cd /tmp/rhel7/
># mkisofs -o /tmp/rhel7test.iso -b isolinux/isolinux.bin -J -R -l -c
isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table
-eltorito-alt-boot -e images/efiboot.img -no-emul->boot -graft-points -V
"RHEL-7.7 Server.x86_64"  .

>^^^ Change the "-V" label accordingly for CentOS 8 to match the CentOS 8
disk label.

>And the critical command for USB drive booting:

># isohybrid --uefi /tmp/rhel7test.iso

I was "thinking" all that was not needed -   the second partition is
"editable" - I change the file - I just need to regenerate grub right - not
the whole ISO.
I was hoping that is why they split this out into two partitions - for just
such an occasion? Just want to add a menu option.

THanks,

Jerry