Do You Need to Reboot Red Hat After Patching?

When maintaining a Red Hat or any Linux distribution system, it’s common to wonder if a reboot is required after applying patches. The answer depends on the nature of the patches applied. Here’s a guide to help you navigate this decision:

1. Kernel Updates

If a kernel update is part of your patch, then a reboot is generally required to activate the new kernel. That said, technologies like KernelCare or Red Hat’s kpatch have emerged, allowing certain kernel patches to be applied without a reboot. Still, their coverage remains relatively limited.

2. System Libraries

Updates to system libraries, especially the C library (glibc), may require a reboot. This is due to numerous running processes possibly having loaded the old library version in memory. While you could restart individual processes, a system reboot ensures everything runs the updated library.

3. Service Specific Updates

If the patch relates to a specific service, such as a web server or database, restarting that specific service usually suffices.

4. Minor Software Updates

For standard software patches that don’t deeply intertwine with the system’s core operation, a reboot isn’t necessary. A simple restart of the application or service will do.

5. Security Advisories

It’s crucial to read security advisories associated with patches. If an advisory recommends a reboot, follow the advice.

Using the needs-restarting Tool

Red Hat provides a handy tool called needs-restarting, part of the yum-utils package. This tool can inform you which services or processes require a restart post-updates:

  • To check services:

    sudo needs-restarting -s
  • To inspect all processes:

    sudo needs-restarting

If the tool lists several core processes, or to ensure all services utilize the updated libraries, consider a reboot.

Best Practices for Patching Production Systems

  • Testing: Always test patches on a staging system before applying them to production.
  • Backups: Ensure you have current backups before patching.
  • Notification: Inform users or stakeholders of any planned maintenance or potential downtime.
  • Monitoring: After patching, monitor the system to ensure stability and performance.

Scheduled maintenance windows are a common practice in many enterprise environments, ensuring updates and potential reboots are organized and cause minimal disruption.