Kernel parameters & tuned.
'Kernel parameter' means two different things: boot-time arguments GRUB hands the kernel, and runtime sysctl knobs you can twist while it's running. Learn both, how to make each persist, and how tuned bundles dozens of them into one named profile.
Kernel parameters and tuned animated tutorial. Boot-time kernel command line via GRUB and grubby, runtime sysctl tunables, persistent sysctl in /etc/sysctl.d, and tuned profiles with tuned-adm. RHCSA EX200 ready.Two things wear the name "kernel parameter": boot-time arguments from GRUB, and runtime sysctl knobs. Tell them apart, make each persist, and let tuned bundle the lot.
- ·The boot-process lesson (where GRUB and the kernel cmdline fit)
- ·Comfortable editing files and running commands as root
- ·Helpful: NAT-and-routing (ip_forward is the running example)
Distinguish boot-time cmdline from runtime sysctl, persist each correctly, and switch tuned profiles for the machine's role.
pace: 9 minutes
Two different things called 'kernel parameter'
The phrase is overloaded. (1) BOOT-TIME parameters are arguments GRUB passes to the kernel on the command line — set once, read as the kernel starts (e.g. quiet, rd.break, selinux=0). (2) RUNTIME parameters are sysctl tunables you can read and change while the system runs (e.g. net.ipv4.ip_forward). Different mechanisms, different persistence — don't confuse them.
Persistence is the recurring trap. A GRUB 'e' edit lasts one boot; grubby makes it permanent. A sysctl -w lasts until reboot; a file in /etc/sysctl.d makes it permanent. tuned, by contrast, IS persistent — its daemon re-applies the chosen profile every boot.
$cat /proc/cmdline$grubby --info=ALL$grubby --update-kernel=ALL --args="X"$grubby --update-kernel=ALL --remove-args="X"$/etc/default/grub$grub2-mkconfig -o /boot/grub2/grub.cfg$sysctl -a$sysctl NAME$sysctl -w NAME=VAL$/etc/sysctl.d/99-x.conf$sysctl --system$tuned-adm active$tuned-adm list$tuned-adm profile NAME$tuned-adm recommend$systemctl enable --now tunedYou ran `sysctl -w net.ipv4.ip_forward=1` and routing started working. After a reboot it stopped. How do you make it permanent?
You need to add a kernel boot argument permanently across all installed kernels. Best command?
What's the relationship between a sysctl name like net.ipv4.ip_forward and the filesystem?
What does a tuned profile like 'throughput-performance' actually do?
These aren't graded — they're just for active recall, which is what actually makes the lesson stick.
Linux boot process
GRUB is where the kernel command line is assembled and where the 'e' one-boot edit (rd.break, init=/bin/bash) lives. See the full chain from firmware to systemd.
keep going — these pair well with what you just learned.
SELinux contexts
Why Apache can't read your file. Watch the policy engine decide — and learn the workflow for fixing denials. RHCSA-ready.
Linux boot process
From power button to login prompt. Every stage in the chain — UEFI, GRUB, kernel, initramfs, systemd — with the rescue moves that save you. RHCSA-ready.
LVM stacking
Layer-by-layer build of an LVM stack: disks → PVs → VG → LVs → filesystem. Then extend live and snapshot. RHCSA-ready.