LPIC-1 Essential System Services and Networking Practice Test 6 — 15 Questions

Question 1

A system administrator notices that the system time is incorrect by several minutes. Which command should be used first to check the status of NTP synchronization?

Accepted Answer

timedatectl. The `timedatectl` command is the correct first step because it shows the current system time, time zone, and NTP synchronization status in a single output. It directly reports whether NTP is active and whether the clock is synchronized, making it the standard diagnostic tool on modern systemd-based Linux distributions.

Answer

ntpdate

Answer

date

Answer

hwclock

Question 2

An Ubuntu 20.04 server needs a static IP address. The administrator has created a netplan YAML file at /etc/netplan/01-netcfg.yaml. What is the next step to apply the configuration?

Accepted Answer

netplan apply. On Ubuntu 20.04, netplan is the default network configuration tool, and the correct command to apply changes from a YAML file in /etc/netplan/ is 'netplan apply'. This command parses the YAML, generates the appropriate backend configuration (systemd-networkd or NetworkManager), and applies it without requiring a reboot. It is the standard, supported method for activating static IP settings on modern Ubuntu systems.

Answer

ifconfig eth0 down; ifconfig eth0 up

Answer

service network-manager restart

Answer

systemctl restart networking

Question 3

A server runs systemd-resolved and uses a VPN. DNS queries fail intermittently. The administrator checks /etc/resolv.conf and finds it is a symlink to /run/systemd/resolve/stub-resolv.conf. Which command should be used to view the effective DNS servers and debug the issue?

Accepted Answer

resolvectl status. B is correct because `resolvectl status` is the native command for querying systemd-resolved's internal state, showing the per-link DNS servers, search domains, and current resolver configuration. Since `/etc/resolv.conf` is a symlink to the stub resolver, `cat /etc/resolv.conf` only shows the stub listener address (127.0.0.53), not the actual upstream DNS servers used by systemd-resolved. `resolvectl status` reveals the effective DNS servers for each network interface, including VPN interfaces, which is essential for debugging intermittent failures.

Answer

cat /etc/resolv.conf

Answer

systemctl restart systemd-resolved

Answer

dig @localhost

Question 4

Which TWO commands are commonly used to start, stop, or restart system services on a Linux system that uses systemd as its init system?

Accepted Answer

service. The `service` command is a legacy tool that works with System V init scripts, but on systems using systemd, it is often mapped to `systemctl` via compatibility wrappers. This allows `service` to start, stop, or restart services on systemd-based distributions, making it a commonly used command for these tasks.

Answer

journalctl

Answer

chkconfig

Answer

init.d

Question 5

On a modern Linux system using systemd-networkd for interface management and systemd-resolved for DNS, which THREE files are typically involved in network configuration and DNS resolution?

Accepted Answer

/etc/systemd/network/10-static.network. On a modern Linux system using systemd-networkd, network interface configuration is defined in .network files within /etc/systemd/network/, such as 10-static.network (Option A). systemd-resolved manages DNS resolution and typically writes to /etc/resolv.conf (Option C) as a symlink to its own stub resolver. /etc/hosts (Option D) is a static host-to-IP mapping file that is consulted by the system's resolver before DNS queries, making it a standard part of DNS resolution. Together, these three files are directly involved in network configuration and DNS resolution under systemd.

Answer

/etc/network/interfaces

Answer

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

Question 6

A small office has a network printer with IP 192.168.1.100. The printer is shared via CUPS. A user reports that they cannot print a document from their workstation. The printer appears in the list of available printers, but when they try to print, the job hangs in the queue with status 'processing'. The administrator suspects the printer may be offline or the CUPS service is not running. Which command should the administrator run first to gather diagnostic information about the printer and its queue?

Accepted Answer

lpstat -t. The `lpstat -t` command shows the complete status of the CUPS print system, including all printers, their queues, and whether they are accepting jobs. Since the job is stuck with 'processing' status, this command will reveal if the printer is idle, disabled, or unreachable, and whether the queue is enabled or paused. It is the first diagnostic step before testing network connectivity or restarting services.

Answer

ping 192.168.1.100

Answer

lpadmin -p printer -E

Answer

systemctl restart cups

Question 7

After a reboot, a server fails to obtain an IP address on its sole ethernet interface. The administrator checks /etc/netplan/01-netcfg.yaml and finds the configuration looks correct. However, the interface shows no IP. The system uses systemd-networkd. Which command should be run next to apply the configuration and bring up the interface?

Accepted Answer

netplan apply. The correct command is 'netplan apply' because the system uses netplan to manage network configuration, which generates backend configuration files for systemd-networkd. After editing the YAML file, 'netplan apply' parses the configuration, applies it to the running system, and triggers systemd-networkd to reconfigure the interface without requiring a full restart of the service.

Answer

ifup eth0

Answer

systemctl restart networking

Answer

systemctl restart systemd-networkd

Question 8

A server in a corporate network uses systemd-resolved for DNS. Internal hostnames (e.g., server.example.lan) fail to resolve, but external names (e.g., google.com) work. The /etc/resolv.conf is a symlink to /run/systemd/resolve/stub-resolv.conf. The administrator checks the systemd-resolved configuration and finds that the internal DNS server is listed globally, but the network interface has no specific DNS set. Which command should be used to assign the internal DNS server to the interface and fix resolution?

Accepted Answer

Run 'resolvectl dns eth0 10.0.0.1' to set the DNS server for the interface.. `resolvectl dns eth0 10.0.0.1` assigns the internal DNS server specifically to the network interface (eth0), overriding the global setting for that interface. In systemd-resolved, per-interface DNS settings take precedence over global DNS servers, so this command ensures that internal hostnames are resolved by the internal DNS server while external names continue to work via the global configuration.

Answer

Add the internal hostnames to /etc/hosts.

Answer

Restart systemd-resolved service.

Answer

Edit /etc/resolv.conf and add the internal DNS server.

Question 9

A company manages a cluster of 50 web servers running Ubuntu 20.04. The servers are configured to synchronize time with an internal NTP server at 10.0.0.100 using the default ntpd. The NTP server itself syncs with external stratum 2 servers. Recently, the security team implemented a restrictive iptables firewall on all servers, allowing only essential services. Several servers in the 10.0.1.0/24 network now report time drift and ntpq -p shows all peers with '?' status. A network engineer runs tcpdump on one affected server and sees no NTP replies from 10.0.0.100. The NTP server's firewall is configured to allow inbound NTP from 10.0.0.0/24 only. The engineer also notes that the server's /etc/ntp.conf contains the line 'restrict 10.0.0.100' (which is incorrect) and that ntpq -crv shows 'sync target not reachable'. Which single action will most directly resolve the synchronization issue for the affected servers?

Accepted Answer

Modify the NTP server's firewall to allow inbound NTP from 10.0.1.0/24.. The affected servers are in the 10.0.1.0/24 network, but the NTP server's firewall only allows inbound NTP from 10.0.0.0/24. Even if the client's firewall permits outbound UDP to port 123, the server will drop the requests because they originate from an unauthorized subnet. Therefore, modifying the NTP server's firewall to accept NTP traffic from 10.0.1.0/24 directly resolves the synchronization issue. Option A (client firewall fix) is necessary but not sufficient because the server will still block the requests. Option B fixes the incorrect restrict line but does not address the firewall. Option D is irrelevant as routing is not the problem.

Answer

Add an iptables rule on the affected server to accept outbound UDP packets to 10.0.0.100 port 123.

Answer

Remove the line 'restrict 10.0.0.100' from /etc/ntp.conf.

Answer

Add a static route on the affected server for 10.0.0.100 via a different gateway.

Question 10

An administrator must grant a contractor temporary, passwordless sudo access to run only /usr/bin/systemctl restart nginx on a production web server. Which entry in a file under /etc/sudoers.d/ best meets this requirement while limiting privilege escalation?

Accepted Answer

contractor ALL=(root) NOPASSWD: /usr/bin/systemctl restart nginx. Least privilege requires specifying both the permitted binary and its exact arguments. Listing the full command with its unit argument confines the contractor to restarting nginx as root without a password, while the absence of wildcards prevents reusing the rule for other services. A dedicated file under /etc/sudoers.d keeps the change auditable and easy to revoke.

Answer

contractor ALL=(ALL) NOPASSWD: /usr/bin/systemctl

Answer

contractor ALL=(root) NOPASSWD: /usr/bin/systemctl restart *

Answer

%contractor ALL=(root) NOPASSWD: /usr/bin/systemctl restart nginx

Question 11

A Linux server uses systemd-resolved for DNS resolution. Users report that hostname resolution fails intermittently. The administrator inspects /etc/resolv.conf and finds it is a symlink to /run/systemd/resolve/stub-resolv.conf with nameserver 127.0.0.53. Which command should the administrator use to verify the current DNS servers and resolution status?

Accepted Answer

resolvectl status. The resolvectl status command provides detailed information about the current DNS servers and resolution configuration for all interfaces. This is essential for diagnosing intermittent resolution failures, as it reveals if multiple interfaces are providing conflicting DNS servers or if fallback DNS is misconfigured.

Answer

cat /etc/resolv.conf

Answer

systemctl status systemd-resolved

Answer

dig @127.0.0.53 example.com

Question 12

A Linux administrator needs to configure a system to use a proxy server for HTTP and HTTPS traffic for all users. Which TWO environment variables should be set in a system-wide profile script to ensure that command-line tools like curl and wget use the proxy? (Choose two.)

Accepted Answer

http_proxy. Setting http_proxy and https_proxy in a system-wide profile script ensures that command-line tools like curl and wget route HTTP and HTTPS traffic through the proxy. These variables are widely recognized and provide comprehensive coverage for web traffic.

Answer

no_proxy

Answer

all_proxy

Answer

ftp_proxy

Question 13

A Linux administrator is troubleshooting a server that cannot resolve external hostnames. The server has a static IP address and can ping 8.8.8.8 successfully. The administrator checks /etc/resolv.conf and finds only 'nameserver 127.0.0.53'. Which command will best help determine the actual DNS servers being used and the resolution path?

Accepted Answer

resolvectl status. The resolvectl status command provides detailed information about the current DNS servers and resolution configuration for all interfaces, which is crucial for diagnosing why external hostnames cannot be resolved despite network connectivity.

Answer

cat /etc/nsswitch.conf

Answer

nslookup google.com

Answer

dig google.com

Question 14

A junior administrator is asked to verify which TCP ports are listening on a Linux server and which processes own them. Which command provides this information directly?

Accepted Answer

ss -tulpn. The ss command with -tulpn is the standard tool on modern Linux to list listening TCP and UDP sockets, show numeric addresses, and map them to owning processes. Netstat -r shows routes, ip link show displays interface state, and lsof -i :22 is limited to a single port. Only ss -tulpn provides a comprehensive view of all listening ports and their processes.

Answer

netstat -r

Answer

lsof -i :22

Answer

ip link show

Question 15

A Linux administrator needs to check the current status of the systemd service named sshd, including whether it is active and its recent log entries. Which command should she run?

Accepted Answer

systemctl status sshd. The systemctl status command provides a concise overview of a unit's state, including whether it is active, the main PID, and recent journal entries. It is the standard systemd tool for checking both status and recent logs, making it the most complete and appropriate choice for the administrator's needs.

Answer

journalctl -u sshd

Answer

service sshd status

Answer

systemctl is-active sshd