Lesson 6.13: Restarts and reboots after updates
Installing an update replaces files on disk, but programs that are already running keep the old version in memory. A web server started last week still uses last week's vulnerable OpenSSL until it's restarted, and the kernel can only be replaced by a reboot. So 'patched' means updated and restarted. Ubuntu leaves hints (/var/run/reboot-required), needrestart lists the services that still run old code, and shutdown schedules a reboot for a quiet hour. In the lab you find what last night's updates left unfinished and finish it.
15 min
You will learn to
- Explain why updated libraries need service restarts
- Read reboot-required and the running kernel
- List outdated services with needrestart
- Restart services and verify
- Schedule a reboot
Key terms
- Shared library
- Code many programs load at start, such as libssl.
- reboot-required
- /var/run/reboot-required: Ubuntu's flag that a reboot is needed; .pkgs lists why.
- needrestart
- Finds processes still using replaced libraries and the kernel status.
- Running kernel
- The kernel in memory now, shown by uname -r; it changes only at boot.
- Livepatch
- Applying some kernel fixes without a reboot.
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