LFCS Practice Test 21 — 15 Questions

Question 1

Refer to the exhibit. The output of 'iptables -L -n' shows the INPUT chain rules. What will happen to an SSH connection attempt from 10.0.0.1?

Accepted Answer

The connection will be accepted. The exhibit shows iptables rules for the INPUT chain. The first rule explicitly accepts SSH (port 22) from 10.0.0.1, so the connection attempt from that source IP will be accepted. Since iptables processes rules sequentially and this rule matches, the packet is accepted immediately without checking subsequent rules or the default policy.

Answer

The connection will be dropped by the first rule

Answer

The connection will be rate-limited

Answer

The connection will be dropped by the default policy

Question 2

An administrator needs to set up a shared directory /project for the group 'projectteam' (GID 5000). All members of the group should be able to create and delete files, but only the file owner can modify their own files. The directory should also ensure that new files inherit the group ownership. Which set of commands achieves this?

Accepted Answer

chown root:projectteam /project; chmod 2770 /project; setfacl -d -m o::--- /project. Option B is correct because it sets the SGID bit (2770) so new files inherit the group 'projectteam', grants rwx to the group, and uses a default ACL with `setfacl -d -m o::---` to remove 'other' permissions, ensuring only the file owner can modify their own files while group members can create/delete but not modify others' files.

Answer

chown root:projectteam /project; chmod 2775 /project; setfacl -m g:projectteam:rwx /project

Answer

chown root:projectteam /project; chmod 2775 /project

Answer

chown root:projectteam /project; chmod 1770 /project; setfacl -m m::rwx /project

Question 3

Refer to the exhibit. The file script.sh has permissions -rwxr-x--- and is owned by root with group 'developers'. A user named 'alice' is a member of the 'developers' group. Which command allows alice to execute the script without changing the file's group ownership?

Accepted Answer

usermod -aG developers alice. Option A is correct because the script's permissions (-rwxr-x---) grant execute permission to the owner (root) and the group (developers), but not to others. Alice is already a member of the developers group, so the command 'usermod -aG developers alice' would not change her group membership (it would simply re-add her). However, the question asks which command allows Alice to execute the script without changing the file's group ownership. Since Alice is already in the developers group, she already has execute permission via the group. The command in A is redundant but does not change group ownership, and it is the only option that does not alter the file's group or permissions in a way that violates the constraint. The core reasoning is that Alice already has group execute permission, so no command is actually needed, but among the options, A is the only one that does not change the file's group ownership.

Answer

chmod o+x script.sh

Answer

chmod u+x script.sh

Answer

chown alice script.sh

Question 4

An administrator runs 'df -h' and notices that /dev/sda1 is 95% full. The administrator needs to identify the largest files in the filesystem. Which command sequence is most efficient?

Accepted Answer

du -sh /* | sort -rh. Option D is correct because it efficiently identifies the largest directories and files at the top level of the filesystem using `du -sh /*` to summarize disk usage per top-level item, then pipes to `sort -rh` to sort by human-readable sizes in descending order. This avoids scanning every single file recursively, making it the fastest approach for a full filesystem.

Answer

find / -type f -size +100M

Answer

ls -lR / | sort -k5 -rn

Answer

find / -type f -exec du -sh {} \;

Question 5

A system administrator needs to change the group ownership of a file to 'developers' and set the setgid bit on a directory. Which two commands accomplish these tasks? (Choose two.)

Accepted Answer

chmod g+s dir. Option A is correct because `chmod g+s dir` sets the setgid bit on a directory, causing new files created within it to inherit the directory's group ownership rather than the creator's primary group. This is a standard Linux permission mechanism for collaborative directories.

Answer

chmod u+s dir

Answer

chown developers: file

Answer

chmod g+s file

Question 6

Based on the exhibit, what is the average CPU idle percentage over the last 15 minutes?

Accepted Answer

65.0%. The average CPU idle percentage over the last 15 minutes is calculated from the 'idle' value in the 'average' row of the 'mpstat' output. In the exhibit, the 'average' row shows an 'idle' value of 65.0, meaning the CPU was idle 65.0% of the time on average across all CPUs over the 15-minute interval. Therefore, the correct answer is 65.0%.

Answer

2.0

Answer

1.5

Answer

2.5

Question 7

Which TWO commands can be used to display the current working directory?

Accepted Answer

pwd. The `pwd` command (B) is the standard POSIX command that prints the full pathname of the current working directory. The shell variable `$PWD` (D) is automatically set by the shell to the current working directory, so `echo $PWD` outputs the same path. Both are valid ways to display the current working directory.

Answer

which pwd

Answer

date

Answer

whoami

Question 8

Refer to the exhibit. An administrator attempts to mount all filesystems using mount -a, but it fails. The error message indicates that UUID=jkl012 is not found. Which of the following is the most likely cause?

Accepted Answer

The swap partition is not formatted or missing.. The error 'UUID=jkl012 not found' indicates that the system cannot locate a device with that UUID. Since the swap partition is typically referenced by UUID in /etc/fstab and is not required for normal filesystem mounting, a missing or unformatted swap partition would cause mount -a to fail when it tries to mount the swap entry. This is the most likely cause because swap is often the only filesystem that can be missing without affecting other mounts, yet mount -a processes all entries including swap.

Answer

The /dev/mapper/vg_data-lv_data device does not exist.

Answer

The NFS share is unreachable.

Answer

The /home filesystem type is incorrect.

Question 9

A server on a corporate network is intermittently losing connectivity. The administrator runs 'tcpdump -i eth0 icmp' and sees 'ICMP time exceeded in-transit' messages from a router. What is the most likely cause?

Accepted Answer

There is a routing loop or the TTL is too low.. The 'ICMP time exceeded in-transit' message indicates that a packet's TTL (Time to Live) has reached zero before reaching its destination. This is most commonly caused by a routing loop, where packets circulate endlessly between routers, or by an initial TTL value that is too low for the number of hops required. The router that decrements the TTL to zero sends this ICMP Type 11 Code 0 message back to the source, as defined in RFC 792.

Answer

There is a mismatch in MTU size.

Answer

The destination host is down.

Answer

A firewall is blocking the packets.

Question 10

Refer to the exhibit. A server is configured with two network interfaces. A user on the 192.168.2.0/24 network reports that they cannot reach the server at IP 10.0.0.5. What is the most likely cause based on the routing table?

Accepted Answer

There is no route on the server to the 192.168.2.0/24 network.. The routing table on the server does not contain a route for the 192.168.2.0/24 network. When the user on that network sends traffic to 10.0.0.5, the server can receive it, but any reply traffic from the server to the 192.168.2.0/24 source address will be dropped because the server has no matching route. Without a route to the source network, the server cannot send return packets, making communication fail.

Answer

The default gateway is misconfigured; it should be 192.168.1.1.

Answer

The server's IP address 10.0.0.5 is not in the same subnet as the default gateway.

Answer

The firewall on eth0 is blocking incoming traffic.

Question 11

Refer to the exhibit. What is the most likely issue with the Apache web server?

Accepted Answer

The DocumentRoot directory does not exist.. The most likely issue is that the DocumentRoot directory does not exist. When Apache starts, it checks for the existence of the directory specified by the DocumentRoot directive (e.g., /var/www/html). If this directory is missing, Apache will fail to serve content and may log an error like 'Primary script unknown' or 'Directory index forbidden', even though the service itself is running and enabled. This is a common misconfiguration after moving or deleting the web root.

Answer

The service is not enabled.

Answer

The main PID is incorrect.

Answer

The service is not running.

Question 12

Based on the exhibit, what is the correct interpretation?

Accepted Answer

The service is running but the unit file has been modified recently and needs reloading. The 'daemon-reload' notice in the systemctl status output indicates that the unit file has been modified on disk but systemd has not yet reloaded its configuration. Running 'systemctl daemon-reload' will re-read the unit files and apply the changes, which is why option C is correct.

Answer

The service is inactive

Answer

The configuration file is corrupt

Answer

The service is failing

Question 13

Refer to the exhibit. Which filesystem is mounted using the XFS filesystem type?

Accepted Answer

/home. The correct answer is A (/home) because the exhibit shows that /home is mounted with the XFS filesystem type, as indicated in the output of the 'df -hT' or similar command. XFS is a high-performance 64-bit journaling filesystem commonly used in Linux for large files and scalability, and it is the default filesystem in RHEL/CentOS 7 and later.

Answer

/boot

Answer

/proc

Answer

/

Question 14

Which TWO commands can be used to display listening TCP ports on a Linux system?

Accepted Answer

ss -tln. The `ss -tln` command displays listening TCP sockets by using the `-t` flag for TCP, `-l` for listening sockets, and `-n` to show numeric addresses and ports without resolving service names. It reads socket information directly from the kernel's netlink interface, making it the modern replacement for netstat on Linux systems.

Answer

nmap -sT localhost

Answer

iptables -L

Answer

lsof -i TCP

Question 15

A backup script must create a compressed archive of the /etc directory, preserving file permissions and timestamps. Which command should be used?

Accepted Answer

tar -czvf backup.tar.gz /etc. Option D is correct because the `tar -czvf` command creates a compressed archive (via gzip) that preserves file permissions and timestamps by default when run as root. The `-c` flag creates the archive, `-z` compresses it with gzip, `-v` provides verbose output, and `-f` specifies the archive filename. Tar is the standard Unix tool for bundling files into a single archive while retaining metadata like ownership, permissions, and timestamps.

Answer

gzip -r /etc > backup.tar.gz

Answer

cpio -ov < /etc > backup.cpio

Answer

rsync -av /etc /backup/etc

LFCS Practice Test 21 — 15 Questions

Exhibit

LFCS Practice Test 21 — 15 Questions

Exhibit