Consider making non-ISO USB images using 'zpool checkpoint'

probonopd commented 3 years ago

Addressing https://github.com/helloSystem/ISO/issues/4, in BSD Now Episode 383: "Scale the tail" it is explained that sing just ZFS it is not possible to generate a writeable pool from read-only media plus read-write media (such as RAM).

https://www.freebsdnews.com/2021/01/01/bsd-now-episode-383-scale-the-tail/

But it is suggested that since few people are using actual DVD media anymore, we could construct non-ISO disk images with ZFS on them (similar to what NomadBSD is doing), but then using zpool checkpoint (think of it as a "pool-wide snapshot").

During the boot process, one could go back to the last checkpoint.

Advantages:

~100 seconds boot time saved
RAM requirement goes from 4GB to ~1GB

Disadvantages:

Does not work from truly read-only media like DVDs
Truly read-only media are preferred for auditing purposes ("I know for sure that no one tampered with the software")
May not work for systems like Ventoy

Maybe we can at least find a way to boot into Xorg from truly read-only media by mounting a few tmpfs in the right places like /etc, /var, /usr/local/etc, /usr/local/var? This way one could at least install the system from a DVD. Is it worth the extra hassle? I don't know.

grahamperrin commented 3 years ago

Wonder whether this approach might work around https://github.com/helloSystem/ISO/issues/75#issuecomment-753476482 uname and other commands not working in single user mode …

probonopd commented 3 years ago

Don't think the topics are related.

probonopd commented 3 years ago

How would one do this to the system one has booted from?

zpool export zroot
zpool import --rewind-to-checkpoint zroot
Cannot unmount '/': Invalid argument

So one would probably only be able to do this from a ramdisk.

helloSystem / ISO

Consider making non-ISO USB images using 'zpool checkpoint' #81