LFCS Practice Test 16 — 15 Questions

Question 1

An administrator wants to print the last field of each line from a CSV file 'data.csv' (comma-separated). Which awk command accomplishes this?

Accepted Answer

awk -F, '{print $NF}' data.csv. `awk -F, '{print $NF}' data.csv` uses `-F,` to set the field separator to comma, and `$NF` represents the value of the last field (NF is the number of fields, so $NF is the last field). This command prints the last column of each line in the CSV file.

Answer

cut -d, -f2 data.csv

Answer

cut -d, -f1 data.csv

Answer

awk '{print $NF}' data.csv

Question 2

Which TWO commands can be used to display the group membership of a user? (Choose two.)

Accepted Answer

id -Gn username. Option A, 'id -Gn username', is correct because the -G flag lists all group IDs the user belongs to and -n converts those GIDs to group names, so it prints every group name the user is a member of. Option D, 'groups username', is correct because the groups command prints the group names that the specified user belongs to, directly showing group membership. Option B, 'cat /etc/passwd | grep username', only shows the user's passwd entry, which contains the primary GID but not supplementary group memberships. Option C, 'id -g username', prints only the primary group ID (or name with -n), not the full set of groups. Option E, 'grep username /etc/group', only finds groups where the username appears in the member list and misses the user's primary group, so it does not reliably display complete group membership.

Answer

cat /etc/passwd | grep username

Answer

id -g username

Answer

grep username /etc/group

Question 3

A server has multiple IP aliases on eth0. Remote hosts cannot reach the secondary IP addresses. What should the administrator check?

Accepted Answer

The ARP flux settings are configured correctly.. When multiple IP aliases are configured on a single Ethernet interface, the kernel may respond to ARP requests inconsistently, a behavior known as ARP flux. This causes remote hosts to receive conflicting MAC addresses for the secondary IPs, preventing connectivity. Correctly configuring ARP flux settings (e.g., using `arp_ignore=1` and `arp_announce=2` via sysctl) ensures the kernel responds only from the appropriate IP and advertises the correct MAC.

Answer

The server's routing table includes routes for the secondary IPs' subnets.

Answer

The interface is set to NOARP.

Answer

The secondary IPs are in the same subnet as the primary.

Question 4

Which TWO commands can be used to view the current routing table on a Linux system?

Accepted Answer

netstat -rn. Option A, netstat -rn, is correct because the -r flag displays the kernel routing table and -n shows addresses numerically, producing the current routing table on a Linux system. Option D, route -n, is correct because the route command with -n prints the kernel IP routing table in numeric form, which is a classic way to view routes. Option B, ifconfig -a, is wrong because it only shows network interface configuration (addresses, flags, MTU), not routes. Option C, ss -tuln, is wrong because it lists TCP/UDP listening sockets, not the routing table. Option E, ip addr, is wrong because it displays interface addresses and link information, not routes (the routing table would be shown with ip route).

Answer

ifconfig -a

Answer

ss -tuln

Answer

ip addr

Question 5

Given the routing table, if the server sends a packet to destination 10.0.1.200, which interface will be used and what is the next hop?

Accepted Answer

eth1 directly to 10.0.1.200. The destination 10.0.1.200 falls within the directly connected network 10.0.1.0/24 on eth1. According to the routing table, this route has a /24 netmask and is marked as directly connected, meaning no next-hop router is needed. The server will ARP for 10.0.1.200 and send the packet directly to that host via eth1.

Answer

eth1 via 10.0.1.1

Answer

eth0 with next hop 10.0.0.1

Answer

eth0 with next hop 10.0.1.200

Question 6

Which THREE steps are required to create a new ext4 filesystem on /dev/sdc1 and ensure it is automatically mounted at /mnt/data at boot? (Choose three.)

Accepted Answer

mkfs.ext4 /dev/sdc1. Option B (mkfs.ext4 /dev/sdc1) is correct because mkfs.ext4 is the command that actually creates a new ext4 filesystem on the specified partition, which is the core requirement of the task. Option C (mkdir /mnt/data) is correct because the mount point directory must exist before the filesystem can be mounted there, and /mnt/data is not guaranteed to exist by default. Option E (add entry to /etc/fstab for /dev/sdc1) is correct because /etc/fstab is the system configuration file that defines filesystems to be mounted automatically at boot, so an entry mapping /dev/sdc1 to /mnt/data is required for persistent mounting. Option A (e2label /dev/sdc1 data) is not required because labeling the filesystem is optional and not necessary to create or auto-mount it. Option D (mount /dev/sdc1 /mnt/data) is not required as a step for boot-time mounting, since the fstab entry handles mounting at boot; a manual mount would only be needed to use it immediately without rebooting.

Answer

e2label /dev/sdc1 data

Answer

mount /dev/sdc1 /mnt/data

Question 7

A DevOps engineer wants to list all running processes sorted by memory usage in descending order. Which command should be used?

Accepted Answer

ps aux --sort=-%mem. `ps aux` lists all running processes, and `--sort=-%mem` sorts them by memory usage in descending order (the minus sign indicates descending). This is the standard way to identify memory-heavy processes for troubleshooting or resource monitoring.

Answer

ps aux --sort=%mem

Answer

ps aux --sort=+mem

Answer

ps aux --sort=-%cpu

Question 8

Based on the exhibit, what is the most likely cause of the blocked task?

Accepted Answer

Disk I/O bottleneck or hung storage. The exhibit shows a process in 'D' state (uninterruptible sleep), which typically indicates the process is waiting for I/O completion from a block device. When a task is blocked in this state for an extended period, it is most likely due to a disk I/O bottleneck or hung storage, as the kernel cannot interrupt this wait. CPU starvation (run queue) and memory leaks (OOM or swapping) produce different process states, making disk I/O the primary suspect.

Answer

CPU starvation

Answer

Memory leak

Answer

Network congestion

Question 9

Which TWO commands can be used to display the current working directory? (Choose exactly two.)

Accepted Answer

echo $PWD. The shell stores the current working directory path in the environment variable `$PWD`, and `echo $PWD` prints its value. This is a reliable way to display the current directory, as the shell updates `PWD` automatically on every `cd` command.

Answer

ls

Answer

dirname

Answer

cd

Question 10

A user 'alice' cannot log in via SSH. The administrator checks /etc/passwd and sees: alice:x:1002:1002::/home/alice:/sbin/nologin. Which command should be used to allow alice to log in with a bash shell?

Accepted Answer

usermod -s /bin/bash alice. The /sbin/nologin shell in the /etc/passwd entry prevents alice from logging in via SSH. The usermod -s /bin/bash alice command changes alice's login shell to /bin/bash, allowing interactive SSH sessions. This directly addresses the shell restriction without altering other account properties.

Answer

usermod -d /home/alice alice

Answer

usermod -u 1002 alice

Answer

useradd -m -s /bin/bash alice

Question 11

Which command displays the amount of free and used memory in the system?

Accepted Answer

free -h. The `free -h` command displays the total, used, and free physical memory (RAM) and swap space in a human-readable format (e.g., GiB, MiB). The `-h` flag converts raw byte counts into appropriate units, making it the correct tool for checking memory usage.

Answer

df -h

Answer

ps aux

Answer

netstat -i

Question 12

A system administrator notices that a web server process (PID 1234) is consuming excessive CPU. They want to trace its system calls to identify the cause. Which command should be used?

Accepted Answer

strace -p 1234. The correct command is `strace -p 1234`, which attaches to the running process (PID 1234) and intercepts all system calls (e.g., read, write, open) made by that process. This allows the administrator to see exactly what the web server is doing at the kernel level, such as excessive file I/O or network operations, which can pinpoint the cause of high CPU usage. Other tools like ltrace, perf, or gdb serve different purposes (library calls, profiling, debugging) and do not directly trace system calls.

Answer

ltrace -p 1234

Answer

perf record -p 1234

Answer

gdb -p 1234

Question 13

A user reports that they cannot run a script because it says 'Permission denied'. The script is owned by root and has permissions -rw-r--r--. Which command would allow the user to execute the script?

Accepted Answer

chmod +x script. The script has permissions `-rw-r--r--`, meaning the owner (root) has read/write, but no execute bit is set for any user. Option B (`chmod +x script`) adds the execute permission for all users (owner, group, others), which allows the user to run the script. Without the execute bit, the kernel will refuse to execve() the file, returning EACCES.

Answer

chmod u+s script

Answer

chmod -w script

Answer

chown user:user script

Question 14

A temporary contractor 'contractor1' has left the company. The administrator needs to remove the user account and all associated files in the home directory. Which command accomplishes this?

Accepted Answer

userdel -r contractor1. The `userdel -r contractor1` command removes the user account and, with the `-r` flag, also deletes the user's home directory and mail spool. This is the standard Linux command to completely remove a user and their associated files, as required by the scenario.

Answer

userdel contractor1

Answer

passwd -d contractor1

Answer

deluser --remove-home contractor1

Question 15

Order the steps to configure a cron job that runs a script every day at 2 AM.

Accepted Answer

Step 1: Run 'crontab -e' to open the crontab editor.
Step 2: Add the line '0 2 * * * /path/to/script'.
Step 3: Save and exit the editor.
Step 4: Run 'crontab -l' to verify the job is scheduled.. The correct order to configure a cron job is: open the crontab file with 'crontab -e', add the cron expression with the correct time fields (minute, hour, day, month, weekday) and the script path, save the file, and then verify with 'crontab -l'. Common mistakes include adding the line before opening the editor, saving before adding, or verifying before editing.

Answer

Step 1: Add the line '0 2 * * * /path/to/script' directly to the crontab.
Step 2: Run 'crontab -e' to open the editor.
Step 3: Save and exit the editor.
Step 4: Run 'crontab -l' to verify.

Answer

Step 1: Run 'crontab -e' to open the editor.
Step 2: Save and exit the editor immediately.
Step 3: Add the line '0 2 * * * /path/to/script'.
Step 4: Run 'crontab -l' to verify.

Answer

Step 1: Run 'crontab -l' to verify existing jobs.
Step 2: Run 'crontab -e' to open the editor.
Step 3: Add the line '0 2 * * * /path/to/script'.
Step 4: Save and exit.