LFCS Practice Test 14 — 15 Questions

Question 1

A system administrator notices that a new 500GB SSD (/dev/sdb) is not being recognized by the system after installation. The server uses UEFI and GPT partitioning. Which command should the administrator run first to verify that the disk is detected by the kernel?

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

Accepted Answer

lsblk. The `lsblk` command lists all block devices recognized by the kernel, including those without a filesystem or partition table. Since the disk is new and not yet partitioned, `lsblk` will show it if the kernel has detected it, making it the correct first diagnostic step.

Answer

fdisk -l /dev/sdb

Answer

cat /proc/cpuinfo

Answer

lsusb

Question 2

Which THREE of the following are valid systemd unit types?

Accepted Answer

target. Option C (target) is a valid systemd unit type: targets group other units and synchronize boot, replacing SysV runlevels (e.g., multi-user.target). Option D (socket) is valid: socket units describe an IPC or network socket that systemd listens on and activates the corresponding service via socket activation. Option E (service) is valid: service units define and control daemons or oneshot processes managed by systemd (e.g., sshd.service). Options A (notification) and B (startup) are not systemd unit types; notification is not a unit type at all, and startup is not a recognized unit suffix, whereas real types include service, socket, target, device, mount, automount, swap, timer, path, slice, and scope.

Answer

notification

Answer

startup

Question 3

A Linux server cannot reach the internet, but internal LAN connectivity works. The output of 'ip route' shows a default gateway of 192.168.1.1, but pinging 8.8.8.8 fails. What is the most likely cause?

Accepted Answer

The default gateway is not reachable or has no internet connectivity.. The default gateway 192.168.1.1 is present in the routing table, but pinging 8.8.8.8 fails while internal LAN connectivity works. This indicates that the gateway itself either cannot be reached (e.g., due to a layer 2 issue or misconfiguration) or, more likely, it has no upstream internet connectivity. Since the default route is configured, the failure is not due to a missing gateway but rather the gateway's inability to forward traffic to external networks.

Answer

The ARP table is corrupted.

Answer

The default gateway is missing.

Answer

DNS resolution is failing.

Question 4

A system administrator wants to combine two network interfaces for increased throughput and fault tolerance. The requirement is that both links are active simultaneously and the system can tolerate a failure of one link without interruption. Which bonding mode should be used?

Accepted Answer

Mode 4 (802.3ad). Mode 4 (802.3ad) is correct because it implements IEEE 802.3ad Link Aggregation Control Protocol (LACP), which allows both links to be active simultaneously for increased throughput while providing fault tolerance. If one link fails, traffic is automatically redistributed across the remaining active links without interruption, meeting the requirement for both active links and failure tolerance.

Answer

Mode 2 (balance-xor)

Answer

Mode 1 (active-backup)

Answer

Mode 0 (balance-rr)

Question 5

A developer reports that a custom daemon fails to start after a reboot. The daemon's unit file is located in /etc/systemd/system/custom.service. Which of the following is the most likely cause?

Accepted Answer

The service is not enabled.. The most likely cause is that the service is not enabled (systemctl enable). Even though the unit file exists in /etc/systemd/system, systemd only starts services automatically at boot if they are enabled. Option B is correct. Option A is incorrect because manually starting the service after installation would work but does not affect boot behavior. Option C is unlikely because SELinux policy blocks would produce a different error (e.g., denial messages). Option D is incorrect because firewall rules do not prevent systemd from starting a service; they affect network connectivity.

Answer

The service was not started manually after installation.

Answer

The SELinux policy blocks the service.

Answer

A firewall rule is blocking inbound connections.

Question 6

Which THREE of the following are valid Linux filesystem types that can be used for root partitions on a modern Linux system?

Accepted Answer

XFS. XFS (A) is a valid Linux native filesystem, long supported as a root filesystem and the default on RHEL/CentOS, so it is correct. Btrfs (D) is a modern Linux copy-on-write filesystem with full root-partition support (including subvolumes and snapshots), making it correct. ext4 (E) is the long-standing default Linux filesystem and fully supports being mounted as the root partition, so it is correct. NTFS (B) is Microsoft's Windows filesystem and FAT32 (C) is a legacy FAT variant; although Linux can mount them via drivers, neither is a valid native Linux filesystem type for a root partition on a modern system.

Answer

NTFS

Answer

FAT32

Question 7

Which THREE statements about Linux network bonding modes are correct? (Choose three.)

Accepted Answer

Mode 0 (balance-rr) can cause out-of-order packet delivery.. Mode 0 (balance-rr) transmits packets in sequential order from the first available slave through the last, then starts over. This round-robin distribution can cause packets belonging to the same TCP session to take different physical paths, leading to out-of-order delivery at the receiver, which may trigger TCP retransmissions and degrade performance.

Answer

Mode 2 (balance-xor) distributes traffic based on packet type.

Answer

Modes 5 and 6 (balance-tlb and balance-alb) require IEEE 802.3ad switch support.

Question 8

Which THREE fields are part of a standard /etc/group entry?

Accepted Answer

Group password (often 'x'). A standard /etc/group entry has four colon-separated fields: group name, group password, group ID (GID), and group members list. Option C (group name) is correct because the first field of each /etc/group line is the group's name, such as 'sudo' or 'developers'. Option A (group password, often 'x') is correct because the second field holds the group password placeholder, typically 'x' when shadow group passwords are used via /etc/gshadow. Option E (group members list) is correct because the fourth field is a comma-separated list of supplementary members of the group. Option B (primary GID of user) is not part of /etc/group; a user's primary GID is stored in the fourth field of /etc/passwd. Option D (home directory of group) does not exist in /etc/group; home directories are per-user fields in /etc/passwd, not per-group fields.

Answer

Primary GID of user

Answer

Home directory of group

Question 9

An administrator needs to check the UUID of a filesystem on /dev/sdb1. Which command should be used?

Accepted Answer

blkid /dev/sdb1. The `blkid` command is specifically designed to locate and display block device attributes, including the UUID and filesystem type. Running `blkid /dev/sdb1` queries the device's superblock and outputs its UUID, making it the correct tool for this task.

Answer

df -h /dev/sdb1

Answer

mount | grep sdb1

Answer

fdisk -l /dev/sdb1

Question 10

A systems administrator is responsible for a production Linux server running CentOS 7 that provides SSH access to users. The administrator decides to tighten security by restricting SSH access to a specific management subnet 10.0.0.0/24. While connected to the server via SSH from a workstation on 10.0.0.50, the administrator adds the following iptables rule: iptables -A INPUT -p tcp --dport 22 -s 10.0.0.0/24 -j ACCEPT followed by iptables -P INPUT DROP. Immediately after the rule change, the administrator loses all connectivity to the server, including SSH. The administrator suspects that the new default policy dropped the existing SSH session. What is the most reliable method for the administrator to regain access to the server without rebooting?

Accepted Answer

Use IPMI or iDRAC to access the server's console and remove or modify the iptables rules.. IPMI (Intelligent Platform Management Interface) or iDRAC (Integrated Dell Remote Access Controller) provides out-of-band management access to the server's console, independent of the operating system's network stack. This allows the administrator to log in locally, remove or modify the iptables rules that dropped the SSH session, and restore connectivity without rebooting. Since the default INPUT policy was set to DROP, all new and existing SSH packets are blocked, but out-of-band management bypasses iptables entirely.

Answer

Use netcat to send a TCP reset packet to the SSH server.

Answer

Use iptables-save and iptables-restore from another host on the same subnet.

Answer

Boot the server into single-user mode and flush iptables rules.

Question 11

A security policy requires that user 'svc_backup' have a password that never expires. Additionally, the account should be locked after 90 days of inactivity. Which set of commands achieves this?

Accepted Answer

chage -M 99999 -I 90 svc_backup. `chage -M 99999` sets the maximum password age to 99999 days, effectively preventing the password from ever expiring (since 99999 days far exceeds any practical lifespan). The `-I 90` flag sets the inactivity period to 90 days, meaning the account will be locked after 90 days of no login activity. This combination satisfies both security policy requirements: a non-expiring password and automatic lockout after 90 days of inactivity.

Answer

chage -W 7 -I 90 svc_backup

Answer

chage -E 2025-01-01 -I 90 svc_backup

Answer

chage -M 90 -I 90 svc_backup

Question 12

Which THREE actions will affect the state of a systemd service that is currently running? (Choose three.)

Accepted Answer

systemctl kill myapp.service. Option A, `systemctl kill myapp.service`, is correct because it sends a signal (SIGTERM by default) to the service's processes, which changes the running state by terminating or signaling them. Option B, `systemctl reload myapp.service`, is correct because it triggers the service's ExecReload action, causing the running process to reload its configuration without stopping, thus affecting its runtime state. Option E, `systemctl stop myapp.service`, is correct because it explicitly stops the running service, transitioning it from active to inactive. Option C, `systemctl disable myapp.service`, only removes the service's autostart symlinks and does not affect a currently running instance. Option D, `systemctl daemon-reload`, only reloads systemd manager configuration and does not alter the state of any running service.

Answer

systemctl disable myapp.service

Answer

systemctl daemon-reload

Question 13

A process is consuming 99% CPU and is unresponsive to normal shutdown requests. After running 'top', you see the PID is 1234. What is the most appropriate command to stop the process gracefully first?

Accepted Answer

kill -15 1234. Kill -15 1234. The SIGTERM signal (15) is the standard way to request a process terminate gracefully, allowing it to clean up resources, close files, and perform shutdown routines. This is the most appropriate first step before escalating to stronger signals, as it gives the process a chance to exit normally.

Answer

kill -19 1234

Answer

kill -2 1234

Answer

kill -9 1234

Question 14

A user wants to view the contents of a compressed log file /var/log/syslog.2.gz without decompressing it first. Which command should they use?

Accepted Answer

zcat /var/log/syslog.2.gz. `zcat` is a utility that reads compressed files (typically gzip-compressed) and outputs their decompressed content to standard output without permanently decompressing the file. This allows the user to view the contents of `/var/log/syslog.2.gz` directly in the terminal.

Answer

gunzip /var/log/syslog.2.gz

Answer

cat /var/log/syslog.2.gz

Answer

less /var/log/syslog.2.gz

Question 15

A large company needs to create 100 user accounts from a list of names in a CSV file. Which tool is most efficient for batch user creation?

Accepted Answer

newusers. The `newusers` command is the most efficient tool for batch user creation because it reads a file in a specific format (username:password:UID:GID:comment:home_directory:shell) and can create multiple user accounts in a single pass, automatically handling password hashing and home directory creation. This avoids the overhead of scripting loops and multiple `useradd` invocations, making it ideal for bulk operations like creating 100 accounts from a CSV list.

Answer

vipw

Answer

for loop with useradd

Answer

pwconv