Short answer: You can defer a reboot only for a specific security fix after your distribution has issued a livepatch for your supported, running kernel and the host confirms that patch is applied. If the vendor requires a kernel upgrade and reboot—or another pending update requires a restart—Livepatch is not a substitute. Check the security notice and the machine’s actual patch status before deciding to wait.
What Livepatch changes—and what it does not
Linux livepatching redirects calls at function entry to updated implementations while the running kernel remains in place. The upstream kernel uses stack-trace checks and task-transition mechanisms to move work to patched code when safe. A transition can take time or remain incomplete if a task stays in the old state. See the upstream Linux livepatch documentation.
This is not the same as booting a new kernel. Only certain functions and code changes can be safely intercepted and patched, and livepatching interacts with tracing and probe mechanisms. So kernel support for livepatch does not mean any arbitrary kernel change can be applied without a reboot.
Canonical describes its Livepatch fixes as a subset of fixes delivered through kernel updates. It targets selected high- and critical-severity kernel vulnerabilities when a safe livepatch can be developed; some code paths cannot be patched this way. Livepatch does not install ordinary APT security updates, nor does it deliver kernel improvements, driver updates, new features, or other fixes outside its scope. See Canonical’s Livepatch documentation.
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When can you defer a reboot?
Treat deferral as a temporary operational decision, not a general permission to postpone kernel maintenance. Before waiting, verify all of the following for the affected host:
- The distribution supports the running kernel, including its release, architecture, version, and flavour.
- The vendor has issued a livepatch for the specific vulnerability and that kernel.
- The local client reports the patch as applied—not pending or requiring a reboot.
- No other pending kernel, system-component, or security update requires a restart.
These checks describe the decision, not a universal command or status interface: distributions expose patch status differently. Use your vendor’s current tooling, security notice, and support matrix.
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Severity is not proof of coverage
A high or critical CVE rating does not mean a livepatch exists for every affected system. Canonical says its service addresses selected high- and critical-severity kernel vulnerabilities identified through Ubuntu Security Notices and the CVE tracker, but a patch must also be safe to develop for the affected code and supported kernel. A vendor notice may instead say that a livepatch cannot be released and that an update and reboot are necessary. Canonical’s Livepatch Security Notices announce new patches or explain when one cannot be released.
When is a reboot required?
- No applicable livepatch exists. This includes cases where the vendor cannot safely patch the affected code while the system runs. Follow the security notice’s mitigation and reboot guidance.
- You need a newer kernel. Livepatch does not upgrade the machine to a newer kernel version. Canonical’s guidance states that a reboot is required to boot into that kernel.
- The change is outside livepatch scope. Kernel bug fixes, performance improvements, driver updates, and new features may arrive in kernel packages that need to be installed and booted.
- The kernel is no longer covered. Unsupported or out-of-window kernels do not gain coverage merely because Livepatch is enabled. Canonical’s support matrix gives platform-specific upgrade-and-reboot intervals of 9–13 months for listed kernels; check the current entry for your exact combination because support details can change.
- Another component needs a restart. Canonical lists CPU firmware or microcode, low-level dependencies such as glibc, and BIOS/EFI updates as examples.
- Ordinary security updates remain pending. Enabling Livepatch does not enable automatic APT security updates. Install the distribution’s normal updates and follow their restart requirements.
How Ubuntu and RHEL differ
Livepatch coverage is vendor- and platform-specific. Do not assume that a patch policy, supported-kernel list, or reboot cadence for one distribution applies to another.
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|---|---|---|
| Canonical Livepatch for Ubuntu | Selected high- and critical-severity kernel vulnerability fixes; Canonical provides a client and hosted service, with an optional on-premises server. The offering is part of Ubuntu Pro. | Current Ubuntu release, architecture, kernel version and flavour in the supported-kernel matrix; service eligibility and terms; notice and client status for the specific vulnerability. |
| Red Hat kpatch for RHEL | Selected important and critical CVE fixes, with eligibility and delivery tied to release, architecture, supported kernel and entitlement. Red Hat’s support article was updated 2026-09-01 and also describes periodic kernel upgrades and reboots; unloading a kpatch from the running kernel is unsupported. | Current Red Hat support guidance, host subscription, exact RHEL release and architecture, supported kernel, and whether a kpatch covers the issue. Consult current-version documentation; the cited RHEL 7 Kernel Administration Guide is specific to RHEL 7 and cautions that not every important or critical CVE receives a livepatch. |
| Reboot into the vendor’s updated kernel | Loads the newer kernel package and applies fixes that require a kernel upgrade rather than a livepatch. | Whether the security notice or package update requires the reboot, and whether other updates or maintenance also need one. |
For Ubuntu, Canonical’s service patches Canonical-released kernels, not arbitrary or privately rebuilt kernels. Its support matrix is organized by release, architecture, kernel version, and flavour. Check the live matrix rather than relying on an old example. For RHEL, use Red Hat’s current kpatch support guidance and documentation for the installed RHEL version.
A practical decision sequence
- Identify the exact issue. Read the vendor’s security notice for the CVE, affected product and kernel, and stated mitigation. Do not infer patch availability from severity alone.
- Confirm host eligibility. Match the running release, architecture, kernel version and flavour against the distribution’s current livepatch support information.
- Check the patch client and notice. Confirm that a patch for this issue is available and applied on this machine. If the vendor says a patch cannot be issued, or the client says a reboot is required, schedule the update and reboot.
- Review other pending updates. Check for a newer kernel and updates to components such as firmware or low-level dependencies. Livepatch does not satisfy restart requirements for those updates.
- If all checks pass, set a bounded deferral. Record why the reboot is being postponed, who owns the decision, and when the host will be checked again. Revisit the vendor notice and update status as part of normal maintenance rather than treating the deferral as indefinite.
What Livepatch is meant to accomplish
Livepatch reduces the need for unscheduled security restarts; it does not eliminate kernel reboots. Its value is operational: selected fixes can be applied while services keep running, giving administrators flexibility to schedule the eventual reboot required by a kernel upgrade or other maintenance. Keep applying normal security updates and plan reboots when the vendor’s instructions or the machine’s pending updates require them.
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