LFCS Practice Test 20 — 15 Questions

Question 1

Which TWO commands can be used to display the routing table on a Linux system? (Choose two.)

Accepted Answer

route -n. The `route -n` command displays the kernel IP routing table with numeric addresses, showing destination, gateway, netmask, and interface. The `ip route` command from the iproute2 suite shows the same routing table with more detail and is the modern replacement for `route`. Both are standard tools for viewing routing information on Linux.

Answer

ss -r

Answer

traceroute

Answer

ping -R

Question 2

To compress a file while preserving the original file, which command should be used?

Accepted Answer

gzip -k file.txt. The `-k` (or `--keep`) flag in `gzip` instructs the utility to compress the file while retaining the original uncompressed file. By default, `gzip` replaces the original file with a compressed version (appending `.gz`), so `-k` is the explicit option to preserve the source file.

Answer

gzip file.txt

Answer

gzip -d file.txt.gz

Answer

gzip -1 file.txt

Question 3

A system administrator is setting up a new backup server. The server has two 4TB disks /dev/sda and /dev/sdb. The administrator decides to create a RAID1 array and then an LVM volume group on top of the RAID device. After creating the RAID1 array /dev/md0, they create a physical volume, volume group named vg_backup, and a logical volume lv_data of size 2TB. Then they format with ext4 and mount at /backup. During testing, they realize that the backup data volume will likely exceed 2TB eventually. They want to expand the filesystem to use all available space in the RAID array. What is the correct procedure?

Accepted Answer

lvextend -l +100%FREE /dev/vg_backup/lv_data, resize2fs /dev/vg_backup/lv_data.. The correct procedure is to extend the logical volume to use all remaining free space in the volume group with lvextend -l +100%FREE, then resize the ext4 filesystem online with resize2fs. Since ext4 supports online resizing, unmounting is not required.

Answer

Unmount /backup, lvextend -l +100%FREE /dev/vg_backup/lv_data, resize2fs /dev/vg_backup/lv_data, mount /backup.

Answer

Create a new logical volume and mount it separately.

Answer

Add new disk to RAID array, then extend LVM.

Question 4

An administrator wants to permanently configure a static IP address on a CentOS 7 system. Which file should be edited?

Accepted Answer

/etc/sysconfig/network-scripts/ifcfg-eth0. On CentOS 7, network interface configuration is stored in individual files under /etc/sysconfig/network-scripts/, named ifcfg-<interface>. The ifcfg-eth0 file contains parameters like BOOTPROTO, IPADDR, NETMASK, and GATEWAY, and setting BOOTPROTO=static along with the IP address values permanently configures a static IP. This is the standard method for RHEL/CentOS 7 systems using the legacy network scripts (not NetworkManager's keyfile format).

Answer

/etc/sysconfig/network

Answer

/etc/hostname

Answer

/etc/network/interfaces

Question 5

Refer to the exhibit. The /var partition is 100% full. Which command can be used to find the largest files in /var/log to free up space?

Accepted Answer

du -ah /var/log | sort -rh | head. It uses `du -ah` to list all files and directories in /var/log with human-readable sizes, pipes the output to `sort -rh` to sort them in reverse numerical order (largest first), and then uses `head` to display only the top entries. This combination efficiently identifies the largest files consuming space, allowing the administrator to target specific files for cleanup.

Answer

ls -lS /var/log

Answer

find /var/log -size +100M

Answer

df -h /var/log

Question 6

An administrator runs 'systemctl status sshd' and sees the output above. The administrator wants sshd to start automatically at boot. Which command should be used?

Accepted Answer

systemctl enable sshd. The `systemctl enable sshd` command creates the necessary symlinks in the systemd unit configuration directories (e.g., `/etc/systemd/system/multi-user.target.wants/`) so that the sshd service is started automatically at boot. This is the correct way to configure a service to start on boot in a systemd-based Linux distribution.

Answer

systemctl reenable sshd

Answer

systemctl mask sshd

Answer

systemctl start sshd

Question 7

An administrator has created an LVM thin pool. Which command should be used to create a thin logical volume named 'thinvol' of size 100GB from the thin pool 'pool1' in volume group 'vg1'?

Accepted Answer

lvcreate -V 100G -T vg1/pool1 --name thinvol. The `lvcreate` command for thin logical volumes requires the `-V` flag to specify the virtual size of the thin volume and the `-T` flag to reference the thin pool. The syntax `-V 100G -T vg1/pool1 --name thinvol` correctly creates a thin logical volume named 'thinvol' with a virtual size of 100GB from the thin pool 'pool1' in volume group 'vg1'.

Answer

lvcreate -L 100G -n thinvol vg1

Answer

lvcreate -s vg1/pool1 -n thinvol

Answer

lvcreate -L 100G -T vg1/pool1 --name thinvol

Question 8

Which command enables a service to start automatically at boot in a systemd-based system?

Accepted Answer

systemctl enable service. The `systemctl enable` command creates the necessary symlinks in the `/etc/systemd/system/` directory tree (typically `multi-user.target.wants/`) to ensure the specified service unit is started automatically when the system boots. This is the standard mechanism in systemd to configure a service for automatic startup at boot time.

Answer

systemctl set-default service

Answer

systemctl daemon-reload

Answer

systemctl start service

Question 9

You manage a Linux server that provides DHCP services to a small office network using the dhcpd daemon. The server has two network interfaces: eth0 (192.168.1.1/24) serving the internal network, and eth1 (192.168.0.1/24) connected to a DMZ. The DHCP server is configured to serve addresses only on eth0. Users on the internal network report that they are not receiving IP addresses. You check the DHCP server and find that the dhcpd service is running and listening on UDP port 67. From a client, you run tcpdump and see DHCPDISCOVER packets being sent, but no DHCPOFFER from the server. You also verify that no firewall rules are blocking DHCP traffic on either side. What is the most likely reason for the failure?

Accepted Answer

The dhcpd configuration file does not have a subnet declaration for the 192.168.1.0/24 network.. The dhcpd daemon will only respond to DHCPDISCOVER packets on interfaces for which it has a matching subnet declaration in its configuration file (typically /etc/dhcp/dhcpd.conf). Without a subnet declaration for 192.168.1.0/24, dhcpd ignores all DHCP traffic on eth0, even though the service is running and listening on UDP port 67. The absence of DHCPOFFER packets despite seeing DHCPDISCOVERs confirms that the server is not processing the requests for that subnet.

Answer

The DHCP server's IP address is not in the same subnet as the clients.

Answer

The dhcpd service is not running.

Answer

The network switch is blocking broadcast packets.

Question 10

An administrator created an LVM snapshot of a logical volume to perform a backup. During the backup, the snapshot runs out of space. What will happen to the original logical volume?

Accepted Answer

The snapshot becomes invalid and must be recreated.. When an LVM snapshot runs out of space, it becomes invalid and cannot track changes made to the original logical volume during the backup. The snapshot is automatically dropped by the device-mapper, and any attempt to mount or read it will fail. The original logical volume remains fully functional and unaffected, but the snapshot must be recreated to perform a new backup.

Answer

The original volume becomes read-only.

Answer

The backup completes successfully but data may be inconsistent.

Answer

The original volume is automatically extended.

Question 11

A user reports that they can access websites by IP address but not by domain name. Which command should the administrator use to diagnose the issue?

Accepted Answer

dig google.com. The user can access websites by IP address but not by domain name, indicating a DNS resolution failure. The `dig` command is the correct diagnostic tool because it directly queries DNS servers to test domain name resolution, bypassing the system's resolver cache and configuration. This allows the administrator to isolate whether the issue lies with DNS resolution or other network layers.

Answer

netstat -r

Answer

traceroute 8.8.8.8

Answer

ping google.com

Question 12

Which THREE are built-in chains in the iptables filter table? (Choose three.)

Accepted Answer

INPUT. The filter table in iptables is used for packet filtering decisions based on IP addresses, ports, and protocols. Its built-in chains are INPUT (for packets destined for the local system), OUTPUT (for packets originating from the local system), and FORWARD (for packets routed through the system). These three chains allow you to control traffic at different points in the packet flow.

Answer

POSTROUTING

Answer

PREROUTING

Question 13

A user must change their password at next login per security policy. The admin wants to expire the password immediately. Which command accomplishes this?

Accepted Answer

chage -d 0 username. The chage -d 0 username command sets the 'last password change' date to 0 (January 1, 1970), which forces the user to change their password at the next login. This is the standard Linux method to immediately expire a user's password without disabling the account.

Answer

passwd -f username

Answer

usermod -p '' username

Answer

chage -M 90 username

Question 14

A system administrator is troubleshooting network connectivity from a Linux server to a remote host at 10.0.0.1. The server has a default gateway of 192.168.1.1. Running `ping 10.0.0.1` fails, but `ping 192.168.1.1` succeeds. The output of `ip route show` shows a default route via 192.168.1.1. Which additional step should the administrator take to further investigate?

Accepted Answer

Run traceroute to 10.0.0.1 to see where packets are dropped.. The ping to the default gateway succeeds, confirming local network and ARP resolution are functional, while the ping to the remote host fails. Running traceroute to 10.0.0.1 will reveal the exact hop where packets are dropped, isolating whether the issue lies in routing beyond the gateway, a firewall along the path, or a missing route on an intermediate router.

Answer

Check the ARP table for 10.0.0.1.

Answer

Verify that the firewall on the remote host allows ICMP.

Answer

Check if the remote host is in the same subnet as the server.

Question 15

Which TWO commands can be used to display the contents of a text file page by page? (Select two.)

Accepted Answer

more file.txt. Option C, more file.txt, is correct because more is a pager that displays a text file one screenful at a time, pausing at each page until the user presses Space or Enter to continue. Option D, less file.txt, is also correct because less is a more advanced pager that likewise presents file contents page by page, while additionally allowing backward scrolling and searching. Both commands satisfy the requirement of paging through a file's contents rather than dumping them all at once. In contrast, A (cat file.txt) writes the entire file to standard output in one continuous stream, B (head file.txt) shows only the first 10 lines by default, and E (tail file.txt) shows only the last 10 lines by default, so none of these paginate the output.

Answer

cat file.txt

Answer

head file.txt

Answer

tail file.txt