LPIC-2 Linux Kernel and System Startup Practice Test 2 — 15 Questions

Question 1

During kernel development, a developer modifies only a few source files in a module directory. Which make target should be used to rebuild only that module without compiling the entire kernel?

Accepted Answer

make M=./drivers/net. The `M=./drivers/net` argument tells the kernel build system to build only the module(s) in the specified directory as external modules, without recompiling the entire kernel tree. This is the standard way to rebuild a single kernel module after modifying its source files, leveraging the already configured kernel build environment.

Answer

make oldconfig && make

Answer

make modules

Answer

make modules_install

Question 2

An administrator needs to disable IPv6 on a running system without rebooting and make the change permanent across reboots. Which set of commands should be used?

Accepted Answer

echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6 && edit /etc/sysctl.conf to add net.ipv6.conf.all.disable_ipv6=1. It combines a runtime sysctl command to immediately disable IPv6 on the running system without a reboot, and a persistent configuration in /etc/sysctl.conf to ensure the setting survives reboots. The /proc/sys/net/ipv6/conf/all/disable_ipv6 file controls the IPv6 stack at runtime, and sysctl.conf applies the kernel parameter at boot time.

Answer

modprobe -r ipv6

Answer

Edit /boot/grub/grub.cfg to add ipv6.disable=1

Answer

sysctl -w net.ipv6.conf.all.disable_ipv6=1

Question 3

Which THREE of the following are standard steps in compiling and installing a custom Linux kernel from source? (Choose three.)

Accepted Answer

make menuconfig. `make menuconfig` is a standard step that launches a text-based menu-driven interface for configuring kernel options before compilation. This step allows the user to select which features, drivers, and modules to include in the kernel build, generating the `.config` file that guides the subsequent compilation.

Answer

make modules_install

Answer

make oldconfig

Question 4

Refer to the exhibit. A system administrator has configured the above in /etc/default/grub. After running update-grub, what will be the boot menu behavior?

Accepted Answer

The menu will be displayed for 10 seconds, then the default entry boots automatically.. The configuration shown in /etc/default/grub includes GRUB_TIMEOUT=10 and GRUB_TIMEOUT_STYLE=menu (or the default style if unset). After running update-grub, the boot menu will be displayed for 10 seconds, and then the default entry (set by GRUB_DEFAULT) will boot automatically. This is the standard behavior when GRUB_TIMEOUT is set to a positive integer and the timeout style is 'menu'.

Answer

The boot menu will be hidden for 0 seconds (i.e., not hidden), and the default entry boots immediately.

Answer

The menu will be displayed but with no timeout; it will wait indefinitely for user input.

Answer

The boot menu will be hidden unless Shift is pressed, and the default entry will boot after 10 seconds.

Question 5

During boot, the system displays 'unable to mount root fs on unknown-block'. What is the most likely cause?

Accepted Answer

Missing filesystem driver in initramfs. The error 'unable to mount root fs on unknown-block' indicates that the kernel cannot find a driver for the filesystem or block device containing the root filesystem. This typically occurs when the initramfs lacks the necessary kernel module (e.g., ext4, xfs, or a storage controller driver like ahci or nvme) to access the root device. The initramfs is responsible for loading essential drivers before the kernel mounts the real root filesystem; if the driver is missing, the mount fails.

Answer

Corrupted init binary

Answer

Wrong block device order

Answer

Incorrect root= parameter

Question 6

Refer to the exhibit. Which module is currently in use by another module?

Accepted Answer

kvm. The `lsmod` command shows that `kvm` has a 'Used by' count of 1, indicating another module is currently using it. The 'Used by' column lists the modules that depend on the given module, so `kvm` is in use by another module (likely `kvm_intel` or `kvm_amd`). This is the correct interpretation because the question asks which module is currently in use by another module, and `kvm` is the one with a non-zero 'Used by' value.

Answer

usb_storage

Answer

kvm_intel

Answer

aesni_intel

Question 7

A company has a fleet of servers running a custom Linux kernel version 5.4. They have developed several in-house kernel modules that interface with proprietary hardware. Due to a security vulnerability, the company decides to upgrade all servers to kernel version 5.10. After upgrading the kernel on a test server, the custom modules fail to load with the error 'Invalid module format' or 'disagrees about version magic'. The system administrator must resolve this issue for all servers. The modules are closed-source and cannot be modified easily. The administrator considers the following options. Question: What is the most effective course of action to load the custom modules on the new kernel?

Accepted Answer

Use modprobe with the --force-vermagic option to bypass the version check.. The most effective course of action given the constraints. The custom kernel modules are closed-source and cannot be recompiled (Option A is not feasible). The error 'Invalid module format' or 'disagrees about version magic' indicates a version magic mismatch between the module and the kernel. Using `modprobe --force-vermagic` bypasses the version magic check, allowing the module to load. Although this is a risky workaround (may lead to instability or security issues), it is the only viable option without source code access. Option C (patching the binary) is also not feasible without source, and Option D does not address the version magic mismatch.

Answer

Recompile the custom kernel modules against the new kernel headers and install them.

Answer

Update the version magic string in the module binary by patching the file.

Answer

Use systemd-modules-load to load the modules later in the boot process.

Question 8

A developer compiled a custom kernel version 5.15.10 and ran 'make modules_install' followed by 'make install' on a system using GRUB 2. After rebooting, the system still boots the old kernel. Which of the following is the most likely cause?

Accepted Answer

The boot loader configuration was not updated. After running 'make install', the GRUB 2 bootloader configuration file (usually /boot/grub/grub.cfg) is not automatically regenerated. The 'make install' target copies the kernel image and System.map to /boot, but it does not run update-grub or grub-mkconfig to add the new kernel entry. Without an updated bootloader configuration, GRUB 2 continues to boot the old kernel entry, even though the new kernel files are present.

Answer

The kernel version string is too long for GRUB 2

Answer

The kernel image was not copied to /boot because the disk was full

Answer

The initramfs was not created for the new kernel

Question 9

Which three of the following are required steps to compile and install a custom Linux kernel from source? (Choose three.)

Accepted Answer

Run 'make modules_install' to install compiled modules. After building kernel modules with 'make', you must run 'make modules_install' to copy the compiled modules into the appropriate directory under /lib/modules/$(uname -r)/, making them available for the kernel to load. This step is essential for any kernel that uses loadable modules, as it populates the module tree with the correct .ko files.

Answer

Run 'update-grub' to regenerate GRUB configuration

Answer

Run 'depmod -a' to generate module dependencies

Question 10

A data center administrator is troubleshooting a server that hangs during boot after a kernel update. The server uses UEFI and GRUB 2. The administrator observes that the server displays the GRUB menu, selects the new kernel entry, but then the screen goes blank and the system does not respond. The administrator can boot the previous kernel from the GRUB menu successfully. Which of the following is the most likely cause of this issue?

Accepted Answer

The new kernel includes a graphics driver that conflicts with the hardware, causing the display to blank. The blank screen after selecting the new kernel, while the old kernel works, strongly indicates a graphics driver conflict. In GRUB 2 with UEFI, the kernel may switch from the UEFI framebuffer to a native graphics driver (e.g., nouveau, i915, amdgpu) that fails to initialize on the specific hardware, causing the display to go blank. The system is not truly hung; it continues booting without console output, which is a known issue with incompatible or buggy kernel graphics drivers.

Answer

The initramfs for the new kernel was not generated

Answer

Secure Boot is enabled and the new kernel is not signed

Answer

The new kernel's root= parameter points to an invalid device

Question 11

A Linux system administrator is tasked with upgrading the kernel on a server running a custom compiled kernel (version 4.19) with many in-house modules. The new kernel (5.10) has significant changes, including a different API for some module functions. After compiling the new kernel and the modules, the system boots but some modules fail to load with 'Unknown symbol' errors. The administrator needs to identify which symbols are missing and fix the modules. Which of the following is the most effective approach?

Accepted Answer

Run 'modprobe --dump-modversions mymodule.ko' and compare with 'cat /proc/kallsyms' to identify mismatches. `modprobe --dump-modversions mymodule.ko` displays the symbol version (CRC) checksums for each symbol the module uses, and comparing these with `/proc/kallsyms` (which lists all symbols exported by the running kernel along with their CRC values) directly pinpoints which symbols have mismatched versions. This is the most efficient method to identify 'Unknown symbol' errors caused by API changes between kernel 4.19 and 5.10, as it reveals exactly which symbols need updating in the module source code.

Answer

Check dmesg for each module load error and recompile modules one by one

Answer

Rename the missing symbols in the source code to match the new kernel's exported symbols

Answer

Use 'nm mymodule.ko' to list all symbols and manually compare with the kernel's symbol table

Question 12

A system administrator has compiled a custom Linux kernel (version 5.15.19) with ext4 filesystem support built as a module. The administrator installed the kernel to /boot and built an initramfs using dracut with default options. After rebooting, the system fails with a kernel panic: 'VFS: Unable to mount root fs on unknown-block(0,0)'. The administrator confirms that the root partition is /dev/sda1 formatted as ext4 and that the kernel configuration includes the ext4 module. The kernel command line includes 'root=/dev/sda1' and 'rd.auto'. The administrator also notices that the initramfs file is only 5 MB in size, which seems smaller than expected. Which of the following is the most likely cause and best solution?

Accepted Answer

The initramfs is missing the ext4 module because dracut did not include it. The administrator should run 'dracut --force --add-drivers ext4 /boot/initramfs-5.15.19.img 5.15.19' to regenerate the initramfs including the ext4 module.. The initramfs is only 5 MB, which is too small to contain the ext4 kernel module and its dependencies. Dracut with default options may not automatically include modules for the root filesystem if they are not already loaded or detected during initramfs generation. Running 'dracut --force --add-drivers ext4' explicitly forces the ext4 module into the initramfs, ensuring the kernel can mount the root filesystem during boot.

Answer

The kernel command line needs the 'rd.shell' parameter to allow interactive debugging. The administrator should add 'rd.shell' to the kernel parameter and boot again to investigate.

Answer

The root filesystem label or UUID is incorrect. The administrator should change the kernel command line to use 'root=LABEL=root' or 'root=UUID=...'.

Answer

The kernel is missing the ext4 module because it was not compiled. The administrator should recompile the kernel with ext4 compiled directly into the kernel (y) instead of as a module.

Question 13

A Linux server uses systemd and is configured with multiple custom kernel modules stored in /lib/modules/$(uname -r)/extra/. The administrator needs to ensure that two specific modules, 'foo' and 'bar', are loaded automatically at boot, with 'foo' loaded before 'bar'. Which two actions will achieve this? (Choose two.)

Accepted Answer

Create a file /etc/modules-load.d/foo-bar.conf containing the lines 'foo' and 'bar' in that order.. The two valid methods are using /etc/modules-load.d/ with a configuration file listing modules in order, and creating a custom systemd service that runs modprobe commands sequentially. Both ensure automatic loading at boot and respect the required order. The other options either use incorrect paths, target initramfs without runtime loading, or rely on non-existent interfaces.

Answer

Add 'foo' and 'bar' to /etc/initramfs-tools/modules and run 'update-initramfs -u'.

Answer

Use 'echo foo > /sys/module/bar/parameters/load' to trigger loading of 'bar' after 'foo' is loaded.

Answer

Add the lines 'foo' and 'bar' to /etc/modules, which is read by systemd-modules-load.service on Debian-based systems.

Question 14

A system administrator is troubleshooting a server that fails to boot because a required kernel module is not being loaded during the initramfs phase. Which two actions should be taken to ensure the module is included and loaded early? (Choose two.)

Accepted Answer

Add the module name to /etc/initramfs-tools/modules on a Debian-based system.. To include a module in the initramfs for early loading, the correct approach depends on the initramfs generation tool. On Debian-based systems using initramfs-tools, the module is listed in /etc/initramfs-tools/modules. On dracut-based systems, the module is added via a configuration file in /etc/dracut.conf.d/. Both require rebuilding the initramfs. Other methods load modules too late or are distribution-specific.

Answer

Add the module to /etc/mkinitcpio.conf in the MODULES array and run mkinitcpio -P.

Answer

Edit /etc/modules and add the module name, then reboot.

Answer

Run modprobe module_name and then reboot the system.

Question 15

An administrator must pass a set of kernel boot parameters to a system managed by GRUB 2 so they persist across kernel package updates. The parameters include a custom console setting and a memory reservation. Which two of the following achieve a persistent, correct result? (Choose two.)

Accepted Answer

Add the parameters to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub and run update-grub. Persistent kernel command line changes on a GRUB 2 system come from editing the source variables in /etc/default/grub and regenerating grub.cfg. Both GRUB_CMDLINE_LINUX and GRUB_CMDLINE_LINUX_DEFAULT feed the generator, so either can carry the custom console and memory reservation arguments across kernel updates. Editing grub.cfg directly, using an RPM-only tool, or regenerating only the initramfs all fail to persist or fail to apply at boot.

Answer

Run grubby --update-kernel=ALL --args="param1 param2" on the Debian host

Answer

Edit the linux line of the desired entry in /boot/grub/grub.cfg directly and reboot

Answer

Set the parameters in /etc/kernel/cmdline and run dracut -f