LFCS Practice Test 9 — 10 Questions

Question 1

Based on the tcpdump output in the exhibit, what can be concluded about the TCP handshake?

Accepted Answer

The TCP three-way handshake completed successfully.. The TCP three-way handshake completes successfully when three packets are exchanged: SYN, SYN-ACK, and ACK. The tcpdump output shows exactly these three packets, confirming a successful handshake. The presence of the final ACK from the client to the server's SYN-ACK indicates that the connection is established.

Answer

The connection attempt failed because only three packets are shown.

Answer

The connection was reset by the remote host.

Answer

The handshake is incomplete because there is no ACK from the server.

Question 2

Arrange the steps to configure a new user account with sudo privileges on a Linux system.

Accepted Answer

Step 1: Create the user account with useradd. Step 2: Set a password with passwd. Step 3: Add the user to the sudo group (e.g., wheel) with usermod -aG. Step 4: Verify sudo access by running a command like 'sudo -l' or 'sudo whoami'.. After creating the user and setting a password, adding to the wheel group grants sudo access. Verification and testing confirm it works.

Answer

Step 1: Create the user account. Step 2: Set a password. Step 3: Test sudo access. Step 4: Add the user to the sudo group.

Answer

Step 1: Create the user account. Step 2: Add the user to the sudo group. Step 3: Test sudo access. Step 4: Set a password.

Answer

Step 1: Add the user to the sudo group. Step 2: Create the user account. Step 3: Set a password. Step 4: Test sudo access.

Question 3

An administrator wants to view the current memory usage in a human-readable format, showing totals for used and free memory. Which command should be used?

Accepted Answer

free -h. The `free -h` command displays memory usage in a human-readable format (e.g., MiB, GiB) and shows totals for used and free memory, including buffers/cache and swap. This directly matches the requirement for a quick, readable summary of memory usage.

Answer

vmstat

Answer

top

Answer

cat /proc/meminfo

Question 4

A network interface eth0 is not receiving an IP address via DHCP. Which command can be used to troubleshoot the DHCP client process?

Accepted Answer

dhclient -v eth0. The `dhclient -v eth0` command runs the DHCP client in verbose mode on interface eth0, which is the correct tool to troubleshoot the DHCP client process. It shows detailed messages about the DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, and DHCPACK exchange, helping identify where the process fails. This directly addresses the issue of the interface not receiving an IP address via DHCP.

Answer

systemctl status dhcpd

Answer

nmcli dev show eth0

Answer

dhcpd -t

Question 5

To display the first 10 lines of a file named 'log.txt', which command is correct?

Accepted Answer

head log.txt. The `head` command is designed to display the first 10 lines of a file by default. Running `head log.txt` outputs the first 10 lines of the file without any additional options, making it the correct choice for this task.

Answer

less log.txt

Answer

tail log.txt

Answer

cat log.txt

Question 6

A systems administrator is troubleshooting a server that runs a database application. The server has 64 GB of RAM and 16 CPU cores. The administrator notices that the system is using a significant amount of swap space even though there is plenty of free memory. The 'free -m' command shows: total memory = 65536, used = 50000, free = 15536, buffers/cache = 10000, swap total = 8192, swap used = 6000. Which of the following is the most likely cause?

Accepted Answer

The vm.swappiness value is set too high.. A high vm.swappiness value (default 60) causes the kernel to aggressively swap out anonymous pages even when ample free memory exists. With 15 GB free and 10 GB in buffers/cache, the system should not be using 6 GB of swap unless swappiness is set too high, forcing premature swapping.

Answer

The vm.dirty_ratio and vm.dirty_background_ratio are set too high.

Answer

The database is configured to use huge pages, which are not swappable.

Answer

The vm.vfs_cache_pressure is set too low.

Question 7

A server needs to forward packets between two networks: 10.0.1.0/24 on eth0 and 10.0.2.0/24 on eth1. Which sysctl parameter must be enabled?

Accepted Answer

net.ipv4.ip_forward = 1. Enabling `net.ipv4.ip_forward = 1` allows the Linux kernel to forward IP packets between network interfaces, which is required for a server to route traffic between the 10.0.1.0/24 and 10.0.2.0/24 subnets. Without this parameter, the kernel drops any packet not destined for the local system, preventing inter-network communication.

Answer

net.ipv4.conf.all.rp_filter = 1

Answer

net.ipv4.conf.all.accept_source_route = 1

Answer

net.ipv4.conf.all.send_redirects = 0

Question 8

A system administrator wants to view the last 10 lines of the system log file '/var/log/syslog' and continue to watch for new lines as they are appended. Which command should be used?

Accepted Answer

tail -n 10 -f /var/log/syslog. The `tail -n 10 -f /var/log/syslog` command first displays the last 10 lines of the file and then uses the `-f` (follow) flag to continuously monitor the file for new appended lines, outputting them in real time. This matches the requirement to both view the last 10 lines and watch for new entries.

Answer

tail -n 10 /var/log/syslog

Answer

less /var/log/syslog

Answer

head -n 10 /var/log/syslog

Question 9

An administrator needs to configure software RAID 5 on three disks /dev/sda, /dev/sdb, /dev/sdc with a spare disk /dev/sdd. Which command correctly creates the RAID array?

Accepted Answer

mdadm --create /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sda /dev/sdb /dev/sdc /dev/sdd. It uses the `--spare-devices=1` flag to designate `/dev/sdd` as a hot spare, while `--raid-devices=3` specifies that only three disks form the active RAID 5 array. The spare disk is listed after the active disks, which is the correct syntax for `mdadm --create`.

Answer

mdadm --create /dev/md0 --level=5 --raid-devices=4 /dev/sda /dev/sdb /dev/sdc /dev/sdd

Answer

mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sda /dev/sdb /dev/sdc

Answer

mdadm --create /dev/md0 --level=5 --raid-devices=3 --spare-devices=1 /dev/sda /dev/sdb /dev/sdc --spare /dev/sdd

Question 10

A storage administrator wants to create a software RAID 10 (1+0) array using six disks. Which mdadm command is appropriate?

Accepted Answer

mdadm --create /dev/md0 --level=10 --raid-devices=6 /dev/sd[abcdef]. It uses the proper mdadm syntax to create a RAID 10 array with six disks. The --level=10 specifies RAID 10 (a striped mirror set), and --raid-devices=6 matches the number of disks provided via the /dev/sd[abcdef] glob, which expands to /dev/sda through /dev/sdf. This command correctly creates a RAID 10 array that combines striping and mirroring across all six devices.

Answer

mdadm --create /dev/md0 --level=10 --raid-devices=6 /dev/sda /dev/sdb /dev/sdc

Answer

mdadm --create /dev/md0 --level=1 --raid-devices=6 --chunk=64 /dev/sd[abcdef]

Answer

mdadm --create /dev/md0 --level=10 --raid-devices=4 /dev/sda /dev/sdb /dev/sdc /dev/sdd