LFCS Certification Kernel Parameter Modification 2

Question 1

Which file would you edit to make the kernel parameter 'net.ipv4.ip_forward=1' persist across reboots on a systemd-based system?

Accepted Answer

/etc/sysctl.conf

Answer

/etc/sysctl.conf is the primary file for persistent kernel parameter settings that survive reboots.

Question 2

What is the effect of running 'sysctl -w vm.swappiness=10'?

Accepted Answer

Changes swappiness only for the current session until reboot

Answer

The -w flag writes the value to the live kernel immediately but does not persist across reboots.

Question 3

Which directory under /proc/sys corresponds to the sysctl key 'kernel.hostname'?

Accepted Answer

/proc/sys/kernel/hostname

Answer

Sysctl keys map to /proc/sys paths by replacing dots with slashes, so kernel.hostname → /proc/sys/kernel/hostname.

Question 4

A sysadmin wants to apply all settings from /etc/sysctl.d/ without rebooting. Which command accomplishes this?

Accepted Answer

sysctl --system

Answer

'sysctl --system' loads settings from all standard sysctl configuration directories including /etc/sysctl.d/.

Question 5

What does the kernel parameter 'kernel.dmesg_restrict=1' control?

Accepted Answer

Restricts dmesg output to privileged users only

Answer

When set to 1, kernel.dmesg_restrict prevents unprivileged users from reading the kernel ring buffer via dmesg.

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