docs VS ostree

ublue is based off of fedora and rpm-ostree, which is what "CoreOS" is today.

What happened was old school CoreOS was A/B partition based: https://github.com/coreos/docs/blob/master/os/sdk-disk-parti...

My memory is hazy but here's how I remember it: After Red Hat acquired CoreOS they rebased the entire thing around rpm-ostree, which is the CoreOS people know today: https://coreos.github.io/rpm-ostree/

At the time there was some anxiety in the community as to what would happen, as there was no direct upgrade path from old CoreOS to new CoreOS. Theoretically if we all believed the kool-aid we were drinking it's just a redeploy, no pets!

Kinvolk came along, forked it, and made Flatcar Linux, which kept the A/B partitioning system, and more crucially, let you just change a config file and all your old CoreOS nodes would just move to Flatcar and then you were good to go. So now if you wanted to stay on the system you were comfortable with you could just use Flatcar. If the composability of rpm-ostree attracted you then new CoreOS have you covered. Red Hat deserves a hat tip here because in their documentation/blog they explicitly mentioned Flatcar as an option for people who wanted to stick with what they know, which I thought was cool and how I discovered it!

Later on Microsoft acquired Kinvolk and and then people raised eyebrows. I have not checked in a while but the folks involved continued to do their thing and run it like a good OSS project, hold public meetings, all that stuff.

I use both and they're both high quality.

Ansible makes mutable changes to the OS, task by task.

Nix is immutable. A new change is made entirely new, and only after the build is successful, all packages are "symlinked" to the current system.

Fedora Silverblue is based on ostree [1]. It works similarly like git, but on your root tree. But it requires you to reboot the whole system for the changes to take effect. Since Nix is just symlinked packages, you don't need to reboot the system.

More detailed explanation here [2].

[1]: https://github.com/ostreedev/ostree

[2]: https://dataswamp.org/~solene/2023-07-12-intro-to-immutable-...

This one is for the ostree bug currently ongoing: https://github.com/ostreedev/ostree/issues/2900

This sounds related to the ostree bug.

I definitely agree that immutability offers considerable value in regards to improving security. But arguably it's insufficient to pull the win over mutable Fedora due to the losses caused by the inability to install the kernel-hardened package and the lack of UKI (Unified Kernel Image) support.

Other hardening guides mention a Unified Kernel Image as another measure to further improve security. Unfortunately, once more, this is (currently) not supported on Fedora Silverblue. I haven't seen it being done on openSUSE Aeon either. Though, once again, I'd love to be corrected!

The fedora crew is working on it through ostree though, so both fedora Silverblue and flatpak will be getting it (as well as true immutability) in the future: https://github.com/ostreedev/ostree/issues/2867

Aside from what has already been mentioned, Unified Kernel Image isn't supported (yet).