na sve flash mam v grub.cfg napr.:
menuentry "xubuntu-16.04.3-desktop-i386" {
set isofile="/boot/iso/xubuntu-16.04.3-desktop-i386.iso"
loopback loop $isofile
linux (loop)/casper/vmlinuz i8042.noloop=1 i8042.nomux=1 file=/cdrom/preseed/xubuntu.seed boot=casper quiet splash iso-scan/filename=$isofile locale=en_US.UTF-8
initrd (loop)/casper/initrd.lz
}
menuentry "xubuntu-16.04.3-desktop-amd64" {
set isofile="/boot/iso/xubuntu-16.04.3-desktop-amd64.iso"
loopback loop $isofile
linux (loop)/casper/vmlinuz.efi i8042.noloop=1 i8042.nomux=1 file=/cdrom/preseed/xubuntu.seed boot=casper quiet splash iso-scan/filename=$isofile locale=en_US.UTF-8
initrd (loop)/casper/initrd.lz
}
menuentry "debian-live-9.3.0-amd64-xfce+nonfree.iso(live)" {
set isofile="/boot/iso/debian-live-9.3.0-amd64-xfce+nonfree.iso"
loopback loop $isofile
linux (loop)/live/vmlinuz-4.9.0-4-amd64 live-media-timeout=3 fromiso=$device/$isofile boot=live config components quiet splash
initrd (loop)/live/initrd.img-4.9.0-4-amd64.
}
menuentry "GPartedLive 0.29" {
set isofile="/boot/iso/gparted-live-0.29.0-1-i686.iso"
loopback loop $isofile
linux (loop)/live/vmlinuz i8042.noloop=1 i8042.nomux=1 live-media-timeout=3 fromiso=$device/$isofile boot=live union=overlay username=user config components quiet keyboard-layouts=en locales="en_EN.UTF-8" noswap noeject toram=filesystem.squashfs ip= nosplash gl_batch net.ifnames=0
initrd (loop)/live/initrd.img
}
pokud to neni zrejme, tak iso soubory jsou na flash v /boot/iso/ , kernel ani init neni potreba vykopirovat, bere se primo z iso, u GParted mam volbu toram ktera system pres aktivaci kopiruje do ram (lze pak usb vyndat a bezi dale), to ale musi podporovat dane distro/iso...