LFCS Practice Test 13 — 15 Questions

Question 1

A technician needs to view the current IPv4 addresses, netmasks, and interface states for all network interfaces on a Linux server. Which command displays this information in a structured, modern format?

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

Accepted Answer

ip addr show. The ip addr show command is the standard modern tool for displaying interface addresses, netmasks, and states. It is part of iproute2 and provides both IPv4 and IPv6 details in a structured format. The other commands either show routing tables, socket statistics, or rely on deprecated tools that do not present the requested information in the required format.

Answer

netstat -rn

Answer

ss -tuln

Answer

ifconfig -a

Question 2

A Linux server has two network interfaces: eth0 (192.168.1.10/24) and eth1 (10.0.0.10/24). The administrator wants to configure the server to route traffic between the two networks. Which two actions are required? (Choose two.)

Accepted Answer

Configure iptables FORWARD rules to accept traffic between the interfaces.. To route traffic between two directly connected networks, the server must have IP forwarding enabled and firewall rules that permit forwarding. Connected routes already exist, so static routes for those networks are not needed. NAT is not required for internal routing, and client gateway configuration is done on the clients, not the server.

Answer

Set the default gateway on both client networks to point to the server's respective interface addresses.

Answer

Enable NAT (masquerading) on the server for both networks.

Answer

Add static routes on the server for both networks.

Question 3

A junior administrator needs to verify that the host can resolve the name db.internal.example.com to an IPv4 address before deploying a database client. The system uses systemd-resolved. Which command queries the configured resolver and displays the answer without relying on the local nsswitch.conf ordering?

Accepted Answer

resolvectl query db.internal.example.com. resolvectl query is the native client for systemd-resolved. It sends the query through the resolver daemon, showing the answer, the link used, and the DNS server that responded. This isolates DNS resolution from nsswitch.conf sources like /etc/hosts, which is exactly what is needed to confirm the configured resolver can resolve the name.

Answer

dig db.internal.example.com

Answer

host db.internal.example.com

Answer

getent hosts db.internal.example.com

Question 4

A technician must verify which network services are listening on TCP ports and which processes own them on a production server. Which command provides this information directly?

Accepted Answer

ss -tlnp. The ss utility with the -tlnp flags enumerates TCP listening sockets, keeps addresses numeric, and shows the owning process for each. This single command answers both parts of the requirement: which ports are listening and which processes hold them. The other tools either display unrelated tables or cover only a single port.

Answer

lsof -i :22

Answer

netstat -rn

Answer

ip neigh show

Question 5

A Linux router has two interfaces: wan0 with address 198.51.100.10/24 and lan0 with address 10.10.0.1/24. Hosts on 10.10.0.0/24 can ping the router's lan0 address but cannot reach any Internet host. The administrator has already enabled net.ipv4.ip_forward=1. Which command is required to allow the internal hosts to reach external networks?

Accepted Answer

iptables -t nat -A POSTROUTING -s 10.10.0.0/24 -o wan0 -j MASQUERADE. Forwarding lets packets pass between interfaces, but private RFC 1918 sources cannot traverse the public Internet. The router must rewrite the source address of outbound packets to its public address, which is done with source NAT. A POSTROUTING MASQUERADE rule on the WAN interface accomplishes this dynamically, using the interface's current address, and enables return traffic to be mapped back to the correct internal host.

Answer

iptables -A FORWARD -i lan0 -o wan0 -j ACCEPT

Answer

ip route add default via 198.51.100.1 dev lan0

Answer

iptables -t nat -A PREROUTING -i wan0 -j DNAT --to-destination 10.10.0.1

Question 6

A system with systemd experiences a service that fails to start due to a 'Failed to start' error with status 203/EXEC. What is the most likely cause?

Accepted Answer

The service unit file has a missing or incorrect ExecStart command. Status 203/EXEC in systemd indicates that the service manager failed to execute the command specified in the service unit file. The most common cause is a missing or incorrect ExecStart directive, such as a typo in the binary path, a missing executable, or incorrect syntax. This error is specific to execution failures, not resource or dependency issues.

Answer

The system has run out of memory

Answer

The service is already running

Answer

The service requires a dependency that hasn't started

Question 7

An administrator needs to assign a temporary IPv4 address of 10.20.30.40/24 to interface enp0s3 for immediate testing. The change should not persist after a reboot. Which command accomplishes this?

Accepted Answer

ip addr add 10.20.30.40/24 dev enp0s3. Temporary address changes are made directly in the kernel with the `ip` utility. Adding an address with `ip addr add` affects only the current runtime state, so a reboot restores the previous configuration. Persistent tools such as NetworkManager or editing configuration files are used when the change must survive restarts.

Answer

nmcli con mod enp0s3 ipv4.addresses 10.20.30.40/24

Answer

ifconfig enp0s3 10.20.30.40 netmask 255.255.255.0 up

Answer

ip route add 10.20.30.40/24 dev enp0s3

Question 8

A Linux server uses NetworkManager and has a wired connection profile named 'Wired connection 1'. The administrator needs to set a static IPv4 address 10.20.30.40/24 with gateway 10.20.30.1, and ensure the change persists across reboots. Which sequence of commands accomplishes this?

Accepted Answer

nmcli con mod 'Wired connection 1' ipv4.addresses 10.20.30.40/24 ipv4.gateway 10.20.30.1 ipv4.method manual && nmcli con up 'Wired connection 1'. The correct approach uses 'nmcli con mod' to alter the existing connection profile's IPv4 settings and set the method to manual, then brings the connection up to apply the changes. This persists the static address and gateway in NetworkManager's configuration, satisfying the reboot requirement. Lower-level ip commands are temporary and do not modify profiles, while creating a duplicate profile or using an invalid command would not achieve the goal.

Answer

nmcli dev modify eth0 ipv4.addresses 10.20.30.40/24 ipv4.gateway 10.20.30.1 ipv4.method manual

Answer

ip addr add 10.20.30.40/24 dev eth0 && ip route add default via 10.20.30.1

Answer

nmcli con add type ethernet con-name 'Wired connection 1' ifname eth0 ip4 10.20.30.40/24 gw4 10.20.30.1

Question 9

A Linux server is configured with two network interfaces: eth0 (192.168.1.10/24) and eth1 (10.0.0.10/24). The default route is via 192.168.1.1. A network administrator wants to ensure that traffic to the 10.0.0.0/24 network uses eth1 and that the source address for that traffic is 10.0.0.10. Which command will achieve this?

Accepted Answer

ip route add 10.0.0.0/24 dev eth1 src 10.0.0.10. To direct traffic for a specific directly attached network out a particular interface and use a specific source address, the ip route add command with the dev and src options is used. This ensures packets to 10.0.0.0/24 leave via eth1 with source 10.0.0.10, fulfilling the requirement without affecting other traffic.

Answer

ip route add 10.0.0.0/24 via 10.0.0.1 dev eth1

Answer

ip route add 10.0.0.0/24 dev eth1

Answer

ip route add default via 10.0.0.1 dev eth1

Question 10

Refer to the exhibit. The administrator wants to create a RAID 1 array using /dev/sdb1 and /dev/sdc1. Which command should be used?

Accepted Answer

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1. RAID 1 (mirroring) requires exactly two devices to provide redundancy by duplicating data across both disks. The `--level=1` parameter specifies RAID 1, and `--raid-devices=2` matches the two partitions /dev/sdb1 and /dev/sdc1.

Answer

mdadm --create /dev/md0 --level=5 --raid-devices=2 /dev/sdb1 /dev/sdc1

Answer

mdadm --create /dev/md0 --level=10 --raid-devices=2 /dev/sdb1 /dev/sdc1

Answer

mdadm --create /dev/md0 --level=0 --raid-devices=2 /dev/sdb1 /dev/sdc1

Question 11

A Linux administrator needs to display the IP addresses and netmasks of all network interfaces on a server. Which command provides this information in a concise, modern format?

Accepted Answer

ip addr show. The 'ip addr show' command is the modern, preferred tool for displaying interface IP addresses and netmasks. It is part of iproute2, which is standard on current Linux systems, and its output clearly shows each interface's addresses in CIDR notation. The other commands either show different information (netstat -i, route -n) or are deprecated and not always installed (ifconfig).

Answer

netstat -i

Answer

route -n

Answer

ifconfig -a

Question 12

Which THREE of the following commands can be used to search for a string in multiple files and display the matching lines?

Accepted Answer

ack 'pattern' /path. Option B, ack 'pattern' /path, is correct because ack is a recursive grep-like search tool that by default searches files under the given path and prints matching lines with filenames. Option C, grep -r 'pattern' /path, is correct because the -r (recursive) flag makes grep descend into directories and display each matching line prefixed by its file. Option D, rg 'pattern' /path, is correct because ripgrep recursively searches the path and outputs matching lines, honoring ignore files by default. Option A, find /path -name '*.txt' -type f, only locates files by name and type; it does not search file contents or display matching lines. Option E, sort /path/file, merely sorts lines of a single file and performs no pattern search.

Answer

find /path -name '*.txt' -type f

Answer

sort /path/file

Question 13

A technician configured a new network interface eth1 on a CentOS 7 server but the interface does not obtain an IPv4 address via DHCP. Which of the following is the most likely cause?

Accepted Answer

NetworkManager is not managing the interface (NM_CONTROLLED=no). When NM_CONTROLLED=no is set in the interface configuration file (/etc/sysconfig/network-scripts/ifcfg-eth1), NetworkManager will not manage that interface. Since dhclient is typically invoked by NetworkManager (or by legacy network scripts only if NM_CONTROLLED=yes), the interface will not automatically obtain an IPv4 address via DHCP. On CentOS 7, NetworkManager is the default network service, and disabling its control prevents DHCP client activation.

Answer

The interface MTU is set too high

Answer

SELinux is blocking dhclient

Answer

Firewalld is blocking DHCP ports (67/68)

Question 14

Based on the exhibit, which process is using the most physical memory (RES)?

Accepted Answer

mysqld (PID 9101). The exhibit shows the output of the `top` command, where the RES column indicates the resident memory (physical RAM) used by each process. mysqld (PID 9101) has a RES value of 2.5g, which is significantly higher than nginx (PID 5678) with 128m and systemd (PID 1234) with 48m, making it the process using the most physical memory.

Answer

Not determinable from exhibit

Answer

nginx (PID 5678)

Answer

systemd (PID 1234)

Question 15

A user wants to view the contents of a compressed file file.txt.gz without decompressing it permanently. Which two commands can be used? (Choose two.)

Accepted Answer

gunzip -c file.txt.gz. Option A, gunzip -c file.txt.gz, is correct because the -c (--stdout) flag writes the decompressed output to standard output, allowing the user to view the contents while leaving the original .gz file intact on disk. Option B, zcat file.txt.gz, is correct because zcat is functionally equivalent to gunzip -c, decompressing the gzip file to stdout without removing or modifying the compressed file. Option C, gzip -l file.txt.gz, only lists metadata such as compressed size, uncompressed size, and ratio, so it does not show the file's contents. Option D, gzip -d file.txt.gz, actually decompresses and deletes the .gz file, which is a permanent decompression, not a view-only operation. Option E, gzip -k file.txt.gz, compresses a file while keeping the original, so it does not display the contents of an already compressed file.

Answer

gzip -l file.txt.gz

Answer

gzip -d file.txt.gz

Answer

gzip -k file.txt.gz