LFCS Certification Kernel Parameter Modification 5

Question 1

What is the maximum value for 'kernel.pid_max' on a 64-bit Linux system?

Accepted Answer

4194304

Answer

On 64-bit systems, kernel.pid_max can be set up to 4,194,304 (2^22), allowing more simultaneous processes.

Question 2

An LFCS candidate needs to harden a server by disabling ICMP redirects. Which sysctl key should be set to 0?

Accepted Answer

net.ipv4.conf.all.accept_redirects

Answer

Setting net.ipv4.conf.all.accept_redirects=0 prevents the kernel from accepting ICMP redirect messages that could alter routing.

Question 3

Which sysctl parameter, when set to 1, enables the kernel's Magic SysRq key functionality?

Accepted Answer

kernel.sysrq

Answer

kernel.sysrq controls Magic SysRq; setting it to 1 enables all SysRq functions for low-level system control.

Question 4

A process is being killed by the OOM killer. Which sysctl parameter controls the minimum amount of free memory the kernel keeps reserved?

Accepted Answer

vm.min_free_kbytes

Answer

vm.min_free_kbytes sets the minimum kilobytes of free memory the kernel attempts to keep available at all times.

Question 5

What does 'net.core.somaxconn' control?

Accepted Answer

The maximum length of the listen backlog queue for sockets

Answer

net.core.somaxconn caps the maximum value for the listen() backlog argument, limiting queued connection requests per socket.

LFCS Certification Practice Test