If you have worked with Fedora CoreOS, you might have noticed that every time you install a package you need to reboot in order for the files from said package to be available to you. This is quite different from other Linux distributions where you can immediately use whatever package you installed without having to reboot every time.
What is the technical reasoning for having to reboot?
rpm-ostree is quite a special tool: It does not just install a package. This has the advantage that the currently running system is not modified at all, but a separate OS tree – image it like an image containing all the files constituting your system – is built after running rpm-ostree install.
While rebooting after every install might seem like a stupid idea since it takes down the entire server, remember that it can save you a lot of headache since there are no partially updated services and you don’t need to manually fix or restart anything since everything is restarted on reboot. This means that your system is always in a consistent state, since every service is cleanly shut down before the system reboot – and after the reboot, every service is cleanly started with the system changes.
Can you install multiple packages before having to reboot?
Yes, you can run multiple rpm-ostree install commands before rebooting. When rebooting, all the changes will be applied at once.
Can you delay the reboot after rpm-ostree install?
Yes, there is no need to reboot immediately after the rpm-ostree command. You can delay the reboot as long as you like. Note however, that when the machine is rebooted for reasons other than a manual reboot (like a power outage or restart of the VM host), the updates will be applied as well, but you might not be there to check if all services are running correctly. Hence, I recommend to reboot as soon as possible.
Can you avoid to reboot after installing packages?
Yes, Fedora CoreOS provides an experimental live update feature using rpm-ostree ex apply-live. See our post How to apply Fedora CoreOS changes without a reboot . Note that applying updates or new packages on a system with productively running services might be a bad idea, but it’s not inherently more unsafe than installing packages on a typical Linux distribution like Debian, Fedora or Ubuntu where every install or update to a package immediately affects the files on the file system.