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Intro to BlueCat

You can think of BlueCat as a template for Fedora Atomic Desktops defining preinstalled apps, services and such. So basically a glorified bash script.

The techical term would be a base OCI image used by Fedora Atomic Desktops.

Fedora Atomic works differently from a regular Linux system. The system is built from an image that acts as a template for the whole root filesystem instead of modifying files by hand. BlueCat is that template.

Installing and Managing Apps

You can’t change most system files directly. This means that stuff like sudo dnf install vlc won't work.

Tip

There is one exception, /etc is writable.

Instead, system level stuff like kernel modules and system wide apps are defined by BlueCat. To install your own apps, Flatpak is used for graphical apps and Homebrew for CLI Apps.

Flatpak is quite literally a desktop version of installing apps from the Google Play Store or Apple App Store. And Homebrew is the replacement for dnf because it doesn't change system files.

How Updates Work

BlueCat uses an update model similar to Android, IOS, ChromeOS and SteamOS. You download the update and then reboot to apply it.

When you run rpm-ostree upgrade (the update command), the system checks for a new image, downloads the new image if it exists, and applies the changes all at once. When you reboot, you change to that new version.

The cool part of this model is that if something goes wrong, you can easily roll back to the version of your OS by just rebooting and selecting to boot in the previous version of the OS before the update.