I daily drive kalpa and also installed it on my family computer. I landed on kalpa after a long time researching, so, let me dump an overview of this new distro tech.
# Terminology
1. Immutable: The core OS (/usr directory) is kept in "pristine" condition by disallowing modifications.
- Discourage installing packages or removing packages.
- well-tested (as most users are running the same OS with same package version)
- System upgrades are an entirely new immutable copy
NOTE: kalpa in particular, uses suse-microos tech called Transactional-Update https://documentation.suse.com/sles/15-SP7/html/SLES-all/cha...
# Atomic styles
4 mainstream models of immutable distros:
1. declarative-config: ALL your system configuration in a config file eg: package versions, network config, user accounts and so on. eg: NixOS, BlendOS
2. OSTree-based: You use cloud/container (OCI) technology (eg: docker files) to layer upon existing layers (eg: pre-baked system images). eg: fedora's atomic spins, vanillaOS, endlessOS. So, fedora coreOS is the base layer -> atomic spins like silverblue/kinoite layer desktop packages like gnome/kde etc.. -> the infamous gaming distro "bazzite" layers gaming packages like wine/steam/drivers etc. and so on.
3. Btrfs-snapshot-based: You take a btrfs snapshot of your root partition before upgrading, so that you can boot into it if the upgrade fails. eg: suse-microos family (kalpa belongs here), chimeraOS
4. systemd-mkosi based: You essentially "curate" an entire OS filesystem in a directory using mkosi and deploy it as an immutable disk image. eg: kdelinux
NOTE: systemd-mkosi is the vision of systemd maintainers as mentioned here: https://0pointer.net/blog/fitting-everything-together.html . There's a whole bunch of system features in development to achieve this ideal.
Most of these distros (except btrfs-based) simply use the A/B root system. They just maintain two root partitions/images, put any upgrade into the "other" partition, mark that as live and the current partition as backup. If the boot into the new partition fails, they just boot into the backup partition and just wait for next upgrade.
As they don't allow usage of system package manager, you are supposed do package management at user level. For gui apps, you resort to flatpak. For other utilities, you usually pick homebrew or language-specific tools like cargo, pip/npm etc..
# The magical tool called Distrobox
This runs containers in userspace and tries to integrate them into your system as much as possible.
A lot of software development requires system level services or shell access or install dependencies etc.. You obviously can't do that on host, as system package management is essentially forbidden and half the point of immutable distros is to keep the host "clean".
So, you create a container and do all your development in there. If it gets too dirty, you just delete it and create a new one.
Personally, I use an arch container for development, as it has all the bleeding edge packages and the convenient AUR too. vscode (from flatpak) supports connecting to containers using official remote extension. I also run a media server inside it. You can also install any system packages or cmdline utilities you want inside it (eg: codecs, ollama, etc..).
# Why kalpa over others?
- Great KDE polish that suse is known for
- btrfs tech is mature and was already used in suse for years, the atomic system is very simple to understand and you can just pick the snapshot you want at boot menu.
- Despite being immutable, customizing the system (eg: installing a driver, kernel modules, firewalls etc. ) is easy too.
- just enter a transactional update shell
- this creates a new mutable snapshot of the current system and chroots into it
- run all the commands you want inside the shell. eg: install/remove packages, enable services etc.
- exit shell. This will mark the transaction as success/complete and set the snapshot as live for next boot.
- Updates are fast/tiny, as they are just routine rolling release updates from tumbleweed repos.
There are some problems too:
- single maintainer
- less popular, compared to alternatives like fedora-based atomic spins.
- It's based on tumbleweed, so, you get lots of tiny updates (almost daily). Fedora based, for example, have weekly/bi-weekly updates.
- still in alpha stage (but once you set it up, it's rock solid).
- Immutability is still a new concept, and flatpaks are rough around the edges. Expect bugs. Mutable/traditional distros are still easier to use, as that has been "the way" forever.