https://fedoraproject.org/wiki/Changes/Automatic_Cloud_Reboot_On_Updates This document represents a proposed Change. As part of the Changes process, proposals are publicly announced in order to receive community feedback. This proposal will only be implemented if approved by the Fedora Engineering Steering Committee. == Summary == Cloud users can provide cloud-init metadata when creating a Fedora cloud instance and that metadata can contain instructions to update all packages on the system and reboot the system if any of those updated packages need a reboot to go into effect. Fedora cloud instances should write the `/var/run/reboot-required` file if a reboot is needed after a dnf update so that cloud-init can reboot the instance. This issue originally surfaced in [https://bugzilla.redhat.com/show_bug.cgi?id=1275409 RHBZ 1275409]. == Owner == * Name: [[User:mhayden| Major Hayden]] * Email: major@xxxxxxxxxx == Detailed Description == Fedora cloud instances use cloud-init to do the initial configuration of the instance. This includes setting up networking, assigning a hostname, adding users/groups, and arbitrary scripts. There are also two options that you can pass to cloud-init that are important for this change: * `package_update`: If set to `true`, all installed packages are immediately updated on first boot * `package_reboot_if_required`: If set to `true`, and the `package_update` step wrote to `/var/run/reboot-required`, reboot the system immediately after updating packages 📚 For more details, see cloud-init's module reference for `[https://cloudinit.readthedocs.io/en/latest/reference/modules.html#package-update-upgrade-install package_update]`. 🚨 '''WAIT A MOMENT. ARE WE TALKING ABOUT REBOOTING EVERY CLOUD INSTANCE ON BOOT?''' 🚨 No! This change would require all three of these things to happen before a reboot occurs: * User provides `package_update: true` on instance creation * '''AND''' user provides `package_reboot_if_required: true` on instance creation * '''AND''' `tracer` notices that at least one of the packages need a reboot to go into effect 🤔 '''Where does this `/var/run/reboot-required` file come from?''' On Debian and Ubuntu systems, `apt` automatically writes to `/var/run/reboot-required` if a reboot is needed after a package update. From there, `cloud-init` looks for the file ([https://github.com/canonical/cloud-init/blob/6d09df5e4786a2a6c79d6098ab413c93b205221c/cloudinit/config/cc_package_update_upgrade_install.py#L119-L134 relevant cloud-init code]) and if present, reboots the system immediately. ✏️ '''How do we write this file on Fedora?''' Fedora systems have a package called `tracer` and a corresponding dnf plugin, `python3-dnf-plugin-tracer`, that analyzes `dnf` updates and provides recommendations on reboots or user logouts to bring updates into effect on the system. A recent [https://github.com/FrostyX/tracer/pull/196 pull request] added support for writing the `/var/run/reboot-required` file when a system reboot is recommended. The `cloud-init` tool can read this file after a package update and reboot if needed. 🔎 '''What does `tracer`'s output look like?''' [root@tracer-testing ~]# tracer You should restart: * Some applications using: sudo systemctl restart NetworkManager sudo systemctl restart auditd sudo systemctl restart chronyd sudo systemctl restart dbus-broker sudo systemctl restart qemu-guest-agent sudo systemctl restart sshd sudo systemctl restart systemd-journald sudo systemctl restart systemd-logind sudo systemctl restart systemd-oomd sudo systemctl restart systemd-resolved sudo systemctl restart systemd-udevd sudo systemctl restart systemd-userdbd * These applications manually: (sd-pam) Additionally, there are: - 3 processes requiring restart of your session (i.e. Logging out & Logging in again) - 1 processes requiring reboot [root@tracer-testing ~]# cat /var/run/reboot-required Tracer says reboot is required 📋 '''What do we need to do?''' Add the `python3-dnf-plugin-tracer` plugin to Fedora cloud images. No additional configuration is necessary. This action pulls in five packages that are about 2.1MB after installation: ======================================================================================= Package Arch Version Repository Size ======================================================================================= Installing: python3-dnf-plugin-tracer noarch 4.1.0-1.fc38 fedora 14 k Installing dependencies: python3-dnf-plugins-extras-common noarch 4.1.0-1.fc38 fedora 69 k python3-psutil x86_64 5.9.2-2.fc38 fedora 271 k python3-tracer noarch 0.7.8-5.fc38 fedora 172 k tracer-common noarch 0.7.8-5.fc38 fedora 22 k Transaction Summary ======================================================================================= Install 5 Packages Total download size: 547 k Installed size: 2.1 M == Feedback == One of the other ideas was to patch `cloud-init` to run `tracer` directly and avoid the `/var/run/reboot-required` file altogether. That would require a lot of work upstream in `cloud-init` to enable the functionality and we would still need the same set of packages installed in Fedora anyway. 🥵 == Benefit to Fedora == This change allows Fedora cloud instances to behave in the same way that Debian-based instances already behave. When users request package updates with a reboot now, `cloud-init` performs the update but never reboots the system. This is an unexpected and confusing result for users who come to Fedora from other distributions. Rebooting automatically could also reduce the attack surface of an instance that just came online since it would immediately reboot to put all package updates into effect on the system. This reduces the time that an unpatched instance is online prior to being fully patched. == Scope == * Proposal owners: This change is fairly isolated and only affects Fedora cloud users who request package updates followed by a reboot in their `cloud-init` metadata. * Other developers: N/A * Release engineering: N/A * Policies and guidelines: N/A * Trademark approval: N/A * Alignment with Community Initiatives: N/A == Upgrade/compatibility impact == Since this change only applies to `cloud-init` on the very first boot of the instance, this wouldn't affect a user upgrading from one version of Fedora to the next. == How To Test == # Ensure you have a cloud image that has an update that needs a reboot (kernel, openssl, etc) # Boot an instance with the following `cloud-init` user data: #cloud-config package_update: true package_upgrade: true package_reboot_if_required: true # Wait for the package updates to finish on the instance and verify that it rebooted after updating == User Experience == First, if a user never uses the `package_upgrade` and `package_reboot_if_required` options in their `cloud-init` user data, they won't be affected by this change. These options are not enabled in `cloud-init` by default. If a user does enable both of these options, they will see their cloud instance come online, apply updates, and reboot if required. Most cloud providers have very fast reboots, so the delay should not be a problem. == Dependencies == Nothing depends on this change. == Contingency Plan == * Contingency mechanism: Push to Fedora 40 if the work cannot be done in time * Contingency deadline: N/A * Blocks release? N/A == Documentation == Guidance for users in a blog post (Fedora Magazine) could be helpful for this change. Many users might not be aware that they had the option to ask for package updates and reboots via `cloud-init` for their Fedora cloud instances. == Release Notes == Fedora cloud instances now automatically reboot when a user requests package updates followed by a reboot on the first boot of the instance. The reboot only occurs if an updated package requires a reboot to go into effect (such as a kernel or critical system library). -- Aoife Moloney Product Owner Community Platform Engineering Team Red Hat EMEA Communications House Cork Road Waterford _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
