PDFs can be used for long term archiving of documents. There is even a PDF version call PDF/A specifically for this use case.
I have some research projects with numerical calculations that I would like to keep for the long term. In general, I am thinking of archiving all of my finished projects and uploading them to an object store.
If I wanted to use Incus to archive a Linux environment, what things would I have to keep in mind? For example, maybe VM instances would make the most sense.
It probably would just be VMs.
System containers that run systemd will eventually be inoperable because systemd has minimum kernel requirements, so there’s no guarantee your environment would still work in five years, a decade, or longer.
Not sure if this is applicable to Alpine, Gentoo, or other images using OpenRC or other non-systemd inits.
Well, running very old systemd on very new kernel is usually not the worse direction to go. The other way around is where things are quite a bit more problematic.
There is one exception to that though, the whole cgroupv1 vs cgroupv2 fiasco as the host systems will basically all be on cgroupv2 now, the host systemd may not support cgroupv1 anymore, yet you may need to boot up a container from a time where cgroupv2 didn’t exist or wasn’t widespread yet…
Outside of that, I’ve managed to run some very very old stuff before. I remember a common demo I had for a while was running a CentOS 3 container just fine under Incus. Though “just fine” here isn’t 100% true. We did need a bit of /proc trickery to prevent ps and some other system tools from crashing due to buffer overflows (they were from a time where those files were much smaller).
Anyway, it always depends what your goal really is. A VM should be safer as far as the ability to run it unmodified in the future, though changes in VM exposed devices or firmware can still mess things up somewhat and require additional work. A container may work in many cases and if it comes to it, you’ll at least have the entire filesystem tree readily available to extract what you want from it.