That used to be easy to do;

UnionFS: https://en.wikipedia.org/wiki/UnionFS

OverlayFS was built for Containers, too: https://en.wikipedia.org/wiki/OverlayFS

LiveOS image/overlay - Fedora Project Wiki: https://fedoraproject.org/wiki/LiveOS_image/overlay

LiveOS image - Fedora Project Wiki https://fedoraproject.org/wiki/LiveOS_image#Home_filesystem re: home.img

Why does ventoy say that selinux=0 is necessary for a persistent volume on a fedora liveusb?

"Ventoy Persistence Plugin" https://www.ventoy.net/en/plugin_persistence.html

livecd-iso-to-disk --overlay-size --home-size-mb NNN: https://github.com/livecd-tools/livecd-tools/blob/main/docs/...