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:
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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.