LFCS Kernel Parameter Modification Questions and Answers

Question 1

A system administrator has just created a new configuration file at `/etc/sysctl.d/99-custom.conf` to tune network parameters.
Which command should be used to apply these new settings immediately without rebooting the system?

Accepted Answer

`sysctl -p`

Answer

`sysctl -a`

Answer

`systemctl restart sysctl.service`

Answer

`load-sysctl /etc/sysctl.d/99-custom.conf`

Question 2

To configure a Linux server as a simple network router, a system administrator needs to enable IPv4 forwarding permanently. What is the recommended method to ensure this setting persists across reboots?

Accepted Answer

Create a file, such as `/etc/sysctl.d/90-routing.conf`, with the content `net.ipv4.ip_forward = 1`.

Answer

Run the command `sysctl -w net.ipv4.ip_forward=1`.

Answer

Add the line `net.ipv4.ip_forward = 1` to the `/etc/rc.local` file.

Answer

Run the command `echo 1 > /proc/sys/net/ipv4/ip_forward`.

Question 3

Which of the following filesystems provides a direct, real-time interface for viewing and modifying kernel parameters?

Accepted Answer

`/proc/sys`

Answer

`/sys`

Answer

`/dev`

Answer

`/etc/sysconfig`

Question 4

A system administrator modifies the kernel's tendency to use swap space by executing the command: `echo 10 > /proc/sys/vm/swappiness`. The server is then rebooted for unrelated maintenance. Assuming no persistent configuration for this parameter exists, what will be the value of `vm.swappiness` after the server boots up?

Accepted Answer

It will revert to the system's default value.

Answer

It will remain 10.

Answer

It will be set to 0.

Answer

The system will fail to boot due to the un-saved configuration change.

Question 5

What is the primary function of the `sysctl -w parameter=value` command?

Accepted Answer

To change a single kernel parameter in the running kernel.

Answer

To write the parameter change permanently to `/etc/sysctl.conf`.

Answer

To watch a parameter for any real-time changes.

Answer

To display all writable kernel parameters.

Question 6

A system administrator adds `vm.swappiness = 20` to the `/etc/sysctl.conf` file. After rebooting, they run `sysctl vm.swappiness` and see the output `vm.swappiness = 60`. Which of the following is the most likely reason the setting was not applied?

Accepted Answer

Another configuration file in `/etc/sysctl.d/` with a later name (e.g., `99-performance.conf`) is setting the same parameter to 60.

Answer

The `sysctl` service is disabled in systemd.

Answer

The `/etc/sysctl.conf` file has incorrect file permissions and could not be read.

Answer

The kernel does not support the `vm.swappiness` parameter.

A system administrator has just created a new configuration file at `/etc/sysctl.d/99-custom.conf` to tune network parameters.Which command should be used to apply these new settings immediately without rebooting the system?

A system administrator has just created a new configuration file at `/etc/sysctl.d/99-custom.conf` to tune network parameters.
Which command should be used to apply these new settings immediately without rebooting the system?