LFCS Certification Kernel Parameter Modification 4

Question 1

An admin creates /etc/sysctl.d/99-custom.conf with 'vm.overcommit_memory=2'. When will this setting take effect without a reboot?

Accepted Answer

After running 'sysctl --system'

Answer

'sysctl --system' reloads all sysctl configuration files from all standard directories including /etc/sysctl.d/.

Question 2

What does setting 'kernel.panic=30' accomplish?

Accepted Answer

Automatically reboots the system 30 seconds after a kernel panic

Answer

kernel.panic=30 causes the kernel to automatically reboot 30 seconds after a kernel panic occurs.

Question 3

Which of the following sysctl parameters is used to control the virtual memory overcommit behavior?

Accepted Answer

vm.overcommit_memory

Answer

vm.overcommit_memory controls whether the kernel allows memory allocations that exceed physical + swap memory.

Question 4

A sysctl parameter written via 'echo 1 > /proc/sys/net/ipv4/ip_forward' is equivalent to which sysctl command?

Accepted Answer

sysctl -w net.ipv4.ip_forward=1

Answer

Writing directly to a /proc/sys file and using 'sysctl -w key=value' both modify the live kernel parameter identically.

Question 5

Which sysctl parameter controls how aggressively the kernel swaps anonymous memory pages to disk?

Accepted Answer

vm.swappiness

Answer

vm.swappiness (0-200) determines how aggressively the kernel reclaims anonymous memory by swapping; lower values reduce swapping.

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