Topic: kernel
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Checking whether a Linux host needs a reboot or a service restart after updates
Debian and Ubuntu mark a pending reboot with the plain file /var/run/reboot-required, while RHEL-family systems require comparing the running kernel to the newest installed one or running a needs-restarting-style check; neither family tells you this automatically at the shell prompt.
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Managing installed kernels on Debian and Ubuntu: cleanup, /boot space, HWE and Livepatch
Old kernel packages accumulate in /boot until apt autoremove clears them; Ubuntu additionally offers a rolling Hardware Enablement (HWE) kernel on LTS releases and Canonical's Livepatch service for applying kernel security fixes without an immediate reboot — both Ubuntu-specific, with no Debian equivalent.
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Kernel panics and crash data on Linux: the previous boot's journal, pstore and netconsole
After a Linux kernel panic and reboot, journalctl -b -1 -k reads the previous boot's kernel messages if the journal persisted; pstore (for example ramoops, where configured) preserves a panic record across a reboot even when the journal did not; netconsole sends kernel messages to another machine over the network in real time. kdump captures a full memory dump and is covered elsewhere.
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Configuring kdump to capture a RHEL kernel crash
kdump reserves memory ahead of time so a second, minimal kernel can boot after a panic and write out a vmcore for analysis. This methodology covers reserving that memory, enabling the service, and why deliberately testing it takes down the host — schedule the test accordingly.
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Setting Linux kernel parameters with sysctl: runtime changes versus /etc/sysctl.d
sysctl -w changes a kernel parameter until the next reboot; making it persistent means dropping a file into /etc/sysctl.d/ and understanding the load order across /usr/lib, /etc and /run. sysctl --system applies every configured file and reports which one wins on a conflict.
Machine-readable: JSON