Though it will probably be a while before I am likely to release any new FR skeleton initrd-latest.gz, assuming no bugs found in current one, I can see issues related to booting of isos and image files that I wish/need to better address eventually. I'm primarily interested by the qemu image or iso boot-from scenario. The issue that remains needing to be addressed is the result of there being a fundamental difference between a 'normal' frugal install and the use of a bootable image (e.g. iso).
As I've said before, FR-based distros were not designed with image booting in mind, so that consideration was not part of the original as-simple-as-possible design, which was intended for normal frugal install only (distro savefolder separation being achieved via distro-names subdirectory). But now that we also wish to be able to boot from bootable image files (such as read-only iso) we get a logical inconsistency in the system arrangements required for both since in original design criteria/expectation the savefolder is put in the frugal install filesystem, but it is of course 'impossible' to write a savefolder into bootable frugal install filesystem image (for example, an iso, which you can think of as an already created, but read-only, frugal install filesystem).
More precisely, there are two factors and associated issues that result from that difference:
1. Normal frugal install is read-writable and can be used to hold the (upper_changes) savefolder. However, a bootable image such as an iso (which can be thought of as an already made frugal install), being read-only, can not be used to hold the (upper_changes) savefolder.
2. Normal FirstRib frugal install achieves distro savefolder (upper_changes) separation via unique per-distro subdirectory name to contain the frugal installation. Most users do not separate bootable image files at all, but instead store them in common directory (e.g. BOOTISOS) hence if you wish to boot one from several stored bootable images some other means of 'separation' (for the likes of their individual upper_changes savefolder) is required to be implemented.
These fundamental differences not only complicate the initrd coding requirement (since has to treat normal subdir-separated frugal installation with different, sometimes complex, code for the case of read-only non-separated bootable image frugal installation), but also has potentially similar effects on any system/user utility maintenance scripts (such as for savefolder maintenance, or management rollback session changes filesystems).
It is a nonsense to ever suggest that the likes of Ventoy or any other find and boot iso/image system in any way itself makes an 'iso-boot' identical in functionality/flexibility as 'normal' frugal install - as I say, there are in fact fundamental differences between normal frugal and bootable image frugal: the bootable image being a read-only filesystem, and having major difference also that users store isos in 'same' directory whereas normal frugal installs are separated into own subdirectories. FIxing these differences (when reasonably possible) involves considerable, often very complex, initrd coding work (and more, since can also effect many system utilities), so anyone who claims otherwise is clearly not appreciating the actual difference and complex/developer-time-consuming coding issues involved to appropriately re-code the initrd and many related system utilities to allow for both types of boot.
I.e. whilst both being forms of frugal install, they are fundamentally different in practice, and no, simple sticking of a single config file in the frugal install root directory (or wherever) that says where to find the save folder does not at all address these fundamental frugal install boot type differences. In fact there is no significant difference between using a grub kernel line argument to define savefolder location (i.e. w_changes=blahblahblah) and a text config file (containing the words w_changes=blahblahblahj) to do the same thing or take precedence. Certainly there is nothing wrong with having such a config file mechanism; it is neither innovative nor unusual to employ such a mechanism when it proves useful; for example to provide a default configuration or to take precedence over grub kernel line provided config arguments (indeed FR initrd has always had that savefolder-location config-savefilemarker/and-more ability via its w_plugin files). However, that is irrelevant really since it is actually internal to initrd/init code complexity that remains required to address the differences between normal frugal install and image-contained frugal install that takes a great deal of work - a config file alone is no more than a piece of information - the code to use that information is the issue - it has to take into account the existing FR initrd/init logic and not mess it up... but it is not the save location that is difficult - it is that fundamental difference between normal frugal install read-write nature and bootimage read-only nature that demands special treatment.
Anyway, I am still considering these fundamental differences and working on alternative ways to properly address them. Basically, if you want boot types of frugal install (normal and bootable image) it would be best to force consistency in structure. However, that is not going to be possible since it is inconvenient on the whole to store bootable images in their own separate (from other isos) subdirectories. The fact one type of frugal install media is read-write and the other read-only means the likes of runtime changeable files should not (in terms of operation consistency) be stored inside the frugal installation, but having to store upper_changes somewhere different would generally be a terrible inconvenience also thus not reasonably avoided. Overall, my priority will continue to be normal frugal install, since a bootable image can always easily be converted into that form (so that is best in my opinion actually), but yes, nice and convenient to be able to boot directly from image, but certainly has some limitations at present particularly if wanting to boot between several FR distro images.
If I thus accept read-only frugal installs (image files) as a special case then the easiest 'workaround' is that the special code needed (or extended) in the FR initrd/init treats boot-images as somewhat different than normal frugal installs in that the upper_changes savefolder will either need a per-distro savefolder name (which I don't like) or will be put into its own subdirectory for use only by its relevant separate FR-based distro. I actually don't like that much either since means boot isos getting handled differently in initrd/init code from normal frugal installs, which adds bloat and complexity to the initrd/init logic and also to utility maintenance scripts. The most recent initrd works fine, using one KLV distro iso, with for example qemu or Ventoy, but, assuming save persistence wanted for all, wouldn't work satisfactorily if two FR-based distros amongst the isos since no mechanism is currently provided to allow them convenient automatic access to their own separate upper_changes savefolders. Normal frugal installs always work fine, no matter how many FR-based distro installs are being used since they each all have their own unique upper_changes savefolder (in the separate frugal install subdirectory).
This is a thread for developers mainly of course, so users who are not also developers don't need to understand or bother about any of the above, though they will find some things that work with normal to-media frugal installations won't work with multiple bootable image boots. These rambles are just part of my thinking... being recorded for me to re-read and re-think later really so don't worry about them.
