LPIC-2 201-450: Linux Kernel

Linux Kernel questions in LPIC-2 201-450 cover building and installing a kernel, generating initramfs, and controlling loadable modules and parameters at boot and runtime.

Build and install

• Source is commonly under /usr/src/linux-<version>; .config holds choices made with make menuconfig or make xconfig.
• make -j$(nproc) compiles; make modules_install puts modules under /lib/modules/$(make kernelrelease).
• make install copies vmlinuz, System.map and config-* to /boot; the boot loader entry still must be regenerated.
• Initramfs needs storage, LVM or RAID modules to mount root. Rebuild with dracut -f or update-initramfs -u.
• lsmod, modinfo, insmod, modprobe, depmod and rmmod are core module tools. modprobe resolves dependencies via modules.dep; insmod does not.
• /etc/modprobe.d/*.conf supports options, blacklist, alias and install. sysctl settings persist under /etc/sysctl.d/.

Worked example

You need e1000e loaded with InterruptThrottleRate=3000 at boot. Create /etc/modprobe.d/e1000e.conf containing options e1000e InterruptThrottleRate=3000. Run modprobe -r e1000e then modprobe e1000e to test. Because the NIC may be needed to mount root, rebuild initramfs so the option is present early. Verify in /sys/module/e1000e/parameters/. Reasoning: modprobe reads modprobe.d, but initramfs carries its own module configuration.

Traps

• Using insmod and expecting dependency or option handling.
• Forgetting depmod after copying a module manually.
• Assuming blacklist blocks an explicit modprobe.
• Editing boot loader files without regenerating the boot entry.