How do I tell whether a kernel update is installed but not yet running?
uname reports the kernel currently executing, while the package database reports installed kernel packages. Installing a new kernel does not normally replace the running kernel immediately. Live-patching products have their own supported coverage and status checks, so do not assume they eliminate every reboot requirement.
Before you start
- An authorised SSH session on the Linux server.
Instructions
1. Record the active kernel
This is the version an application is actually using now. Capture it before maintenance and again after the planned reboot.
uname -rRead the full release string, including distribution build details.
2. Inspect the distribution’s installed kernel packages
Use the package family appropriate to the server. Package names vary between generic, cloud and vendor kernels, so adapt the query to the installed image.
dpkg-query -W -f='${Package} ${Version} ${Status}\n' 'linux-image-*'Debian/Ubuntu: distinguish installed packages from residual package records.
rpm -q kernel-coreRHEL-family systems commonly package the active kernel as kernel-core; verify the package naming used by your release.
Check the result
- After an approved reboot, uname -r matches the intended boot entry and the server’s critical services pass their health checks.
Troubleshooting
- The old kernel remains active after reboot
- Inspect the configured boot entry, provider kernel boot mechanism and whether the restart actually occurred. Do not delete older kernels while investigating.
- No listed package matches the running kernel
- The image may use a custom or provider-managed kernel, or you may be inside a container.
Official references
Use the documentation for your installed version when a flag, service name or platform feature differs.