LFCS Practice Test 27 — 15 Questions

Question 1

A Linux server uses systemd-resolved for DNS resolution. Users report that queries for internal hostnames such as 'db.corp.example.com' are failing, while external names resolve correctly. The administrator runs 'resolvectl status' and sees that the interface eth0 has DNS servers 10.0.0.53 and 'DNS Domain: corp.example.com'. Which command should be used to query the internal DNS server directly and verify that it responds to the name?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

dig @10.0.0.53 db.corp.example.com. To verify that the internal DNS server at 10.0.0.53 can resolve the hostname, the administrator should query it directly with 'dig @10.0.0.53 db.corp.example.com'. This bypasses systemd-resolved and tests the server's response. If the server answers correctly, the problem lies in systemd-resolved's configuration, such as a missing routing domain or incorrect DNS server assignment for the interface.

Answer

resolvectl query db.corp.example.com

Answer

nslookup db.corp.example.com 10.0.0.53

Answer

systemd-resolve --status

Question 2

A junior administrator created a user account with the command `useradd -m devuser`. The account was created without a password, and the administrator now wants to set an initial password so the user can log in. Which command should the administrator use to assign a password to the account?

Accepted Answer

passwd devuser. Assigning an initial password to an existing account is done with passwd followed by the username when executed as root. That command prompts interactively for the new secret, hashes it, and writes it to /etc/shadow, immediately enabling authentication. The other commands either expect a pre-hashed string, manage unrelated metadata, or apply only during account creation, so none of them sets a usable password here.

Answer

usermod -p devuser

Answer

chage -p devuser

Answer

useradd -p devuser

Question 3

A Linux server uses LVM for its data volume /dev/vg_data/lv_app. The volume group vg_data has 30 GB of free extents and the logical volume lv_app is currently 100 GB. An administrator runs `lvextend -L +20G /dev/vg_data/lv_app` and receives a success message, but `df -h /app` still reports 100 GB. The filesystem on lv_app is ext4. Which command must the administrator run next to make the additional space usable?

Accepted Answer

resize2fs /dev/vg_data/lv_app. Extending an LVM logical volume with lvextend changes only the block device mapping; the ext4 filesystem inside keeps its original size until resized. Running resize2fs against the LV path grows the filesystem online to fill the new extents, after which df reflects the additional capacity. The XFS-only grow tool, a consistency checker, and a PV-level resize command all fail to accomplish this here.

Answer

e2fsck -f /dev/vg_data/lv_app

Answer

xfs_growfs /app

Answer

pvresize /dev/vg_data/lv_app

Question 4

A Linux administrator wants to view the current resource limits (such as CPU and memory) applied to a running systemd service named database.service. Which command will display these limits?

Accepted Answer

systemctl show database.service. To view the effective resource limits of a running service, systemctl show is the appropriate command. It outputs all properties, including CPUQuota, MemoryLimit, and other cgroup-related settings. systemctl status and cat do not show the current effective limits, and list-dependencies is unrelated.

Answer

systemctl cat database.service

Answer

systemctl status database.service

Answer

systemctl list-dependencies database.service

Question 5

A Linux server is configured to boot into a graphical target, but after a recent kernel update, the system hangs at a black screen after the GRUB menu. You can still access a rescue shell via the installation media. Which command should you use to make the system boot into a multi-user text target by default, allowing you to troubleshoot?

Accepted Answer

systemctl set-default multi-user.target. The default systemd target is managed via the default.target symbolic link. To change it persistently, the systemctl set-default command is used. Setting it to multi-user.target ensures the system boots to a text console, allowing the administrator to diagnose the graphical failure. This is the standard method for altering the default runlevel equivalent in systemd-based distributions.

Answer

systemctl isolate multi-user.target

Answer

grub2-mkconfig -o /boot/grub2/grub.cfg

Answer

systemctl enable multi-user.target

Question 6

An administrator is diagnosing why a server cannot reach the host 198.51.100.25. The server has one interface, eth0, with address 192.0.2.10/24. Running `ip route show` returns only the default route via 192.0.2.1. Which two commands will help determine whether the problem is at layer 2 or layer 3? (Choose two.)

Accepted Answer

ip neigh show 192.0.2.1. To isolate layer 2 versus layer 3, check the neighbor table for the gateway and trace the path to the destination. An unresolved neighbor entry points to a layer 2 problem, while a resolved entry with a traceroute that stops beyond the first hop points to layer 3 or higher. Interface state and DNS queries do not make this distinction.

Answer

ss -tulnp | grep 198.51.100.25

Answer

ip link show eth0

Answer

dig +short 198.51.100.25

Question 7

A system administrator is troubleshooting a server that fails to boot because the root filesystem, which is on an LVM logical volume, cannot be found. The administrator suspects that the initramfs does not include the necessary LVM modules. Which command should be used to rebuild the initramfs for the currently running kernel on a Debian-based system?

Accepted Answer

update-initramfs -u. On Debian-based systems, the initramfs is managed with update-initramfs. Running update-initramfs -u regenerates the image for the current kernel, incorporating any needed modules such as LVM. Other tools like dracut or mkinitrd are used on different distributions and are not the default on Debian, and grub-mkconfig only updates the bootloader configuration.

Answer

grub-mkconfig -o /boot/grub/grub.cfg

Answer

dracut -f

Answer

mkinitrd -f /boot/initrd.img-$(uname -r)

Question 8

You need to check the default gateway on a Linux server. Which command displays the current routing table, including the default route?

Accepted Answer

ip route show. The correct command is 'ip route show', which displays the routing table including the default route. The other commands show interface configuration (ifconfig), interface statistics (netstat -i), or listening sockets (ss -tuln), none of which reveal the default gateway.

Answer

ifconfig -a

Answer

ss -tuln

Answer

netstat -i

Question 9

A Linux server has a single Ethernet interface eth0. The administrator needs to assign a static IPv4 address 192.0.2.10/24 with gateway 192.0.2.1 on a system that uses systemd-networkd. Which file should be created or edited to configure this interface?

Accepted Answer

/etc/systemd/network/10-eth0.network. systemd-networkd uses .network files stored in /etc/systemd/network/ (or /run and /usr/lib). A file such as 10-eth0.network with a [Match] section for eth0 and a [Network] section specifying Address=192.0.2.10/24 and Gateway=192.0.2.1 is the correct way to assign a static IPv4 configuration. The other paths belong to different network management frameworks.

Answer

/etc/network/interfaces

Answer

/etc/netplan/01-netcfg.yaml

Answer

/etc/sysconfig/network-scripts/ifcfg-eth0

Question 10

A technician must create a hard link named 'report_link' to an existing file '/data/report.txt'. Which command should be used?

Accepted Answer

ln /data/report.txt report_link. The ln command without options creates a hard link by default. This results in two directory entries pointing to the same inode, which is exactly what a hard link is. The other commands either create symbolic links, copies, or rename the file, none of which produce a hard link as required.

Answer

cp /data/report.txt report_link

Answer

mv /data/report.txt report_link

Answer

ln -s /data/report.txt report_link

Question 11

An administrator needs to change the group ownership of the directory /srv/project and all of its existing contents to the group developers, without altering the user ownership. Which command should be used?

Accepted Answer

chgrp -R developers /srv/project. Changing group ownership recursively is the job of chgrp -R. It applies only the group change and leaves user ownership intact, which is precisely what the scenario requires. chown with a bare name targets the user, chmod alters permissions rather than ownership, and usermod operates on account definitions instead of filesystem objects.

Answer

chmod -R g+developers /srv/project

Answer

usermod -g developers /srv/project

Answer

chown -R developers /srv/project

Question 12

A Linux administrator needs to modify the default runlevel (target) on a systemd-based Linux server so that it boots into a graphical environment by default. Which command should the administrator use?

Accepted Answer

systemctl set-default graphical.target. The default systemd target is controlled by the /etc/systemd/system/default.target symlink. The systemctl set-default command is the official way to change this symlink to point to the desired target, such as graphical.target for a graphical boot. Unlike isolate, which only changes the current state, set-default persists across reboots. Using enable is incorrect because it does not alter the default.target symlink. Manual symlink creation is possible but not the recommended practice.

Answer

systemctl enable graphical.target

Answer

ln -sf /usr/lib/systemd/system/graphical.target /etc/systemd/system/default.target

Answer

systemctl isolate graphical.target

Question 13

A junior administrator needs to create a new empty file named report.txt in the current working directory. They want to ensure that if the file already exists, its contents are not altered. Which command should they run?

Accepted Answer

touch report.txt. The touch command is designed to create empty files or update timestamps without modifying existing content. Redirection methods like echo > or cat > would truncate the file if it already exists, risking data loss. mkdir creates a directory, not a file. Therefore, touch is the correct choice for safely creating an empty file.

Answer

mkdir report.txt

Answer

echo > report.txt

Answer

cat > report.txt

Question 14

A Linux server is experiencing performance issues. You need to identify which processes are consuming the most CPU and memory in real-time. Which two commands can provide this information interactively? (Choose two.)

Accepted Answer

top. top and htop are interactive process viewers that display real-time CPU and memory usage per process. vmstat and iostat provide system-wide statistics but lack per-process detail and interactivity. ps aux gives a static snapshot, not real-time updates. Therefore, top and htop are the correct choices.

Answer

iostat

Answer

vmstat

Answer

ps aux

Question 15

A Linux server has two interfaces: enp3s0 (192.168.10.5/24) and enp4s0 (10.0.0.5/24). The default route is via 192.168.10.1. A junior admin adds a static route to 10.1.0.0/16 via 10.0.0.1 using the command: ip route add 10.1.0.0/16 via 10.0.0.1. After this, users report that traffic to 10.1.1.0/24 fails. Which command should the administrator run to confirm that the kernel is selecting the correct route and interface for destination 10.1.1.10?

Accepted Answer

ip route get 10.1.1.10. The kernel chooses routes based on longest prefix match and metric. To verify which route and interface are selected for a specific destination, the ip route get command is used. It performs a route lookup and displays the resolved source address, gateway, and output interface, directly answering why traffic to 10.1.1.0/24 may fail despite a static route being added.

Answer

ip -s link show enp4s0

Answer

ip route show table all

Answer

traceroute -n 10.1.1.10