Clarity wrote: Sat Oct 30, 2021 6:56 pmWhen booted, PUPs & DOGs, today, continue behaving, as always, allowing session persistence within their framework(s).
Well, session persistence doesn't happen by itself. It is a matter of coding (which is what I assume you mean by 'their framework), and particularly the method by which it is arranged to work by code inside the initrd/init script (usually). Of the various forms of save persistence, the most common is that of saving back to either a file or folder on the partition the linux kernel and initrd is stored. But when booting from an iso file, you cannot save back into the iso file, so the partition/directory where that iso file is stored 'might', most likely, be used for save persistence location (if the internal initrd/init code is designed to do that for boot from iso file situation). Such persistence mechanisms may work out of the box with Ventoy with many distros, on most occasions, but perhaps with not all optional boot modes.
With WDL, for example, it is possible to arrange booting inside an iso by specifying /mnt/sr0 as the location to boot from - to WDL that implies (meaning is interpreted by the initrd/init shell script code as to use dir / as the location on the cdrom where kernel is and thus location for save file/folder, but for boot from iso scenarios that isn't going to work since cdrom is read/only and what really needs to be used in boot from iso file situation will be something like /dev/sdb1/BOOTISOS/.
That is the issue in a nutshell - so depends how the distro initrd/init shell script is designed to arrange matters - so to use boot from iso file method may well require substantially modified initrd/init code - just depends on the original design. The distro's initrd/init knows nothing about Ventoy and doesn't care or need it - unless that init file has been specially designed/coded to be able to know to use, for example, /dev/sdb1/BOOTISOS for saving back to even when being booted directly via an iso file.
WDL basically provides/understands three main ways to find the kernel being: 1. directly (e.g. /mnt/sdb2/WDL_dir, or, say, /mnt/sr0/) - but that's a simple unreliable location specification since system can randomly assign sd letters to actual devices, particularly when usb hardware; 2. via specified UUID; 3. via specified LABEL.
WIth SG2D some new code has been added to allow special treatment of .iso files (the initrd/init) and to accordingly then determines the rw partition/dir to put the save persistence information. For SG2D boot from iso file capability, the iso designer just needs to provide a suitably configured loopback.cfg file and all will basically work, even when isolinux.cfg just says to use /mnt/srX (the cdrom). Ventoy doesn't provide the same info via any loopback.cfg file but instead reads the main isolinux.cfg line, hence not so easy to fix the issue (since simple /mnt/srX won't work with Ventoy), but should be possible in WDL boot configs to use LABEL boot method rather than /mnt/srX - i.e. have a LABEL assigned to the iso file, and boot via that and all should be well for Ventoy use (I think). This is just off the top of my head - I haven't focussed on the matter or tried it further.