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Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →Usually, yes: installing a newer Linux kernel package does not make the system run it. A reboot is normally required to start the new kernel. A distribution-supported live-patching service can apply certain fixes to an eligible running kernel without rebooting, but it does not cover every vulnerability or replace routine kernel upgrades and maintenance restarts.
Does a Linux kernel patch require a reboot?
It depends on what “patch” means. Installing a newer kernel package and applying a live patch to the kernel already running are different operations. After a normal kernel package upgrade, the machine continues running its existing kernel until it restarts. Canonical’s Ubuntu guidance says a reboot is required to upgrade to a newer kernel: When to reboot.
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A live patch can apply a selected security fix to a running kernel without loading a new kernel through a reboot. That is useful for deferring some restarts, but only when the distribution provides a compatible patch for the specific system and issue. Ubuntu limits Livepatch to high- and critical-severity kernel vulnerabilities, and not every vulnerability can be fixed this way. Red Hat and SUSE also describe limits on which fixes their live-patching systems can address.
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Can I patch the Linux kernel without rebooting?
Sometimes. Use only the live-patching mechanism supported for your distribution and exact kernel build; do not assume that a tool advertised for Linux supports every distribution or kernel. Canonical states: “Live kernel patching is not sufficient when you need to upgrade your kernel to a newer version — a reboot is required in that case.” See How kernel live patching works.
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Ubuntu
Ubuntu Livepatch covers eligible high- and critical-severity kernel vulnerabilities, not all security issues. Support is limited to listed combinations of Ubuntu release, architecture, kernel version, and kernel flavor. Canonical says it creates security patches for a given kernel for up to 9–13 months from that kernel’s release; to continue receiving Livepatch patches, upgrade to a supported kernel and restart within the applicable window. Check the current kernels covered by Livepatch. Enabling Livepatch does not turn on automatic APT security updates, so manage ordinary package updates and notices separately.
Red Hat Enterprise Linux 9
Red Hat’s kpatch can apply selected kernel updates to a running RHEL 9 kernel without rebooting or restarting processes, but it cannot address every critical or important CVE. Live patches follow Red Hat’s published cadence; a kernel outside that cadence may need to be updated before it receives further patches. Red Hat identifies kpatch with RPM modules from Red Hat repositories as the only live-patching utility it supports, and says it does not support third-party live patches. Consult the current RHEL 9 kernel-management guidance and support policy before relying on coverage: Applying patches with kernel live patching.
SUSE Linux Enterprise Server 16.0
SUSE describes live-patch packages tied to exact kernel revisions. They cover critical fixes temporarily, until a regular kernel update and reboot. Some fixes cannot be converted into live patches, making a restart the way to apply them. SUSE’s manual says: “Live patches contain only critical fixes, and they do not replace regular kernel updates that require a reboot.” The manual states that Live Patching is included in the standard SLES subscription; confirm current terms and coverage for the specific release. See Kernel Live Patching on SUSE Linux Enterprise Server.
How much downtime does a kernel update need?
There is no reliable universal downtime figure. It depends on the machine, workload, services, update, and restart process; the vendor guidance cited here does not establish an average outage duration. A reboot is a system restart, but its service impact varies: a single machine may be unavailable while it shuts down and starts, whereas a redundant system may be maintained through its normal failover or rolling-maintenance process.
For planning, treat live patching as a way to defer some restarts, not a promise of zero downtime. Check pending security and package notices, confirm the running kernel is covered, stage updates using the distribution’s documented process, and schedule a maintenance window for the eventual kernel upgrade and reboot. Firmware, service, or other package changes may also require action.
Can I live-patch an unsupported Linux distribution?
“Unsupported” is not a single Linux-wide status. Support can depend on the distribution vendor, release, package component, subscription, architecture, and exact kernel build. The published support of Canonical, Red Hat, or SUSE for their own products does not establish support for an unrelated distribution. If the release or kernel is outside a vendor’s live-patching matrix, ask that distribution’s vendor whether it supports the proposed tool and build before using it on production systems.
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For Ubuntu specifically, Canonical lists 5 years of security maintenance for LTS Main/Restricted packages under standard coverage, 10 years with ESM Infrastructure, and 15 years with ESM Legacy. The 10- and 15-year coverage requires Ubuntu Pro. These are Ubuntu package-support periods, not a general promise of kernel live-patch coverage or a policy shared by other distributions. See Ubuntu Security.
What should I check before relying on live patching?
- Platform match: Confirm the distribution release, architecture, exact kernel version, and kernel flavor against the vendor’s current matrix.
- Fix coverage: Check which severity levels and types of fixes are eligible; a live-patching service does not necessarily cover every vulnerability.
- Coverage window and cadence: Find out how long that kernel receives live patches, how often they are issued, and what happens when the kernel falls out of coverage.
- Terms and support: Verify subscription requirements and whether the distribution vendor supports the proposed live-patching utility and patch source.
- Normal update workflow: Keep installing ordinary security updates and plan for the kernel upgrade and restart that live patches defer rather than eliminate.
Can something besides a kernel update require a reboot?
Yes. Ubuntu’s reboot guidance lists CPU firmware or microcode, shared libraries and low-level dependencies such as glibc, and BIOS or EFI updates as possible reasons for a restart. The package or vendor notice for the specific update should determine whether and when to reboot; do not assume that live-patching the kernel removes other restart requirements.
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