LFCS Practice Test 15 — 15 Questions

Question 1

A system administrator needs to permanently configure a network interface named ens33 with a static IPv4 address of 192.168.1.100/24 and a default gateway of 192.168.1.1 on a system using NetworkManager. Which command should the administrator use to achieve this?

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

Accepted Answer

nmcli connection modify 'ens33' ipv4.addresses 192.168.1.100/24 ipv4.gateway 192.168.1.1 ipv4.method manual. It uses the `nmcli` command to modify the NetworkManager connection profile for interface ens33, setting a static IPv4 address with CIDR notation and a default gateway, and explicitly setting the method to 'manual' to ensure the configuration persists across reboots. NetworkManager is the default network service on modern Linux distributions, and `nmcli` is the proper tool for permanent configuration changes.

Answer

ip addr add 192.168.1.100/24 dev ens33

Answer

ifconfig ens33 192.168.1.100 netmask 255.255.255.0 up

Answer

route add default gw 192.168.1.1 ens33

Question 2

The command 'ss -tuln' shows port 80 is listening on a server, but a remote client cannot connect via HTTP. What is the most likely cause?

Accepted Answer

A firewall is blocking incoming TCP port 80. The `ss -tuln` command shows that port 80 is in the LISTEN state, which means the HTTP service (e.g., Apache or Nginx) is bound to the port and ready to accept connections. Since the server is listening but the remote client cannot connect, the most likely cause is a firewall (such as iptables, nftables, or a cloud security group) that is blocking incoming TCP SYN packets destined for port 80, preventing the three-way handshake from completing.

Answer

The HTTP service is not running

Answer

The client has a misconfigured default gateway

Answer

The server's /etc/hosts file is misconfigured

Question 3

Which THREE files are directly related to user and group management in a Linux system? (Select three.)

Accepted Answer

/etc/group. The three files directly related to user and group management are /etc/group (C), /etc/passwd (D), and /etc/shadow (E). /etc/passwd stores user account entries with UID, GID, home directory, and login shell, making it a core user-management file. /etc/group defines group names, GIDs, and group membership lists, so it is essential for group management. /etc/shadow stores encrypted password hashes and password-aging fields for local users, which is a fundamental part of user account administration. /etc/sudoers (A) controls sudo privilege delegation, and /etc/login.defs (B) sets defaults for login and user-creation tools; both are related to authentication or account policy, but they are not the primary user/group database files.

Answer

/etc/sudoers

Answer

/etc/login.defs

Question 4

A user reports that they cannot delete a file named 'important.txt' located in their home directory. The file is owned by the user and the user has write permission on the directory. Running 'rm important.txt' produces the error: 'rm: cannot remove 'important.txt': Operation not permitted'. The user has also tried using 'sudo rm' but gets the same error. Which of the following is the most likely cause and correct solution?

Accepted Answer

The file has the immutable attribute set. Use 'lsattr important.txt' and if the 'i' attribute is present, remove it with 'chattr -i important.txt'.. The error 'Operation not permitted' despite the user owning the file and having write permission on the directory indicates a filesystem-level restriction rather than a permission or ACL issue. The immutable attribute (i) on the file prevents any modification, including deletion, even by the root user. Running 'lsattr' reveals the attribute, and 'chattr -i' removes it, allowing deletion.

Answer

The file has an ACL that denies deletion. Use 'setfacl -b important.txt' to remove ACLs.

Answer

The file is currently in use by another process. Use 'lsof' to find the process and kill it.

Answer

The directory has the sticky bit set, preventing deletion. Use 'chmod o-t .' to remove the sticky bit.

Question 5

An administrator receives a report that a specific directory /var/log is consuming too much disk space. Which command should be used to determine the total disk space used by that directory?

Accepted Answer

du -sh /var/log. The `du -sh /var/log` command calculates the total disk space used by the specified directory. The `-s` flag summarizes the total size, `-h` provides human-readable output (e.g., in KB, MB, GB), and the path `/var/log` targets the directory in question. This is the standard Linux command for determining directory disk usage.

Answer

df -h /var/log

Answer

ls -la /var/log

Answer

fdisk /var/log

Question 6

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. 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

Question 7

An administrator has enabled quotas on the /home filesystem by adding usrquota,grpquota to /etc/fstab and remounting. Then ran quotacheck -cug /home and it completed successfully. However, users are still able to write beyond their assigned soft limits. What step is missing?

Accepted Answer

Running quotaon to activate quotas.. The missing step is activating quotas with `quotaon`. Even after configuring `/etc/fstab` with `usrquota,grpquota`, remounting the filesystem, and running `quotacheck -cug` to create the quota database files (`aquota.user` and `aquota.group`), quotas remain inactive until explicitly enabled with `quotaon`. Without this command, the kernel does not enforce quota limits, allowing users to exceed soft limits without warning.

Answer

Setting limits with edquota.

Answer

Running repquota to view quotas.

Answer

Setting limits with setquota.

Question 8

A system administrator is managing a web application running as a systemd service on a new Linux server. The application requires a specific environment variable, DATABASE_URL, to be set before starting. The administrator has created a custom service unit file at /etc/systemd/system/webapp.service with the following content:

[Unit]
Description=Web Application Service

[Service]
ExecStart=/usr/local/bin/webapp
Restart=on-failure

The administrator prefers to keep configuration separate from the unit file for easier updates. The service fails to start. Upon investigation, the administrator notices that the DATABASE_URL variable is not being passed to the process. What is the most appropriate course of action to ensure the environment variable is correctly set?

Accepted Answer

Add EnvironmentFile=/etc/webapp.env in the [Service] section and place the variable in that file. Using EnvironmentFile allows the administrator to keep the DATABASE_URL variable in a separate file, which can be updated without modifying the unit file. Option A hardcodes the variable in the unit file, reducing flexibility. Option C only sets the variable in the current shell session and does not persist for the service. Option D modifies ExecStart but is less standard and less maintainable than using EnvironmentFile.

Answer

Add an Environment directive in the [Service] section: Environment=DATABASE_URL=value

Answer

Export the DATABASE_URL variable in the shell before running systemctl start webapp

Answer

Modify the ExecStart line to: ExecStart=/usr/bin/env DATABASE_URL=value /usr/local/bin/webapp

Question 9

A user reports that a shell script 'backup.sh' in /home/user/scripts fails to execute. What is the most likely cause?

Accepted Answer

The script does not have execute permission for the user.. The most likely cause is that the script lacks execute permission for the user. In Linux, a file must have the execute bit set (e.g., `chmod +x backup.sh`) to be run as a script. Without it, the shell will refuse to execute the file, even if the user has read access and the script is syntactically correct.

Answer

The script is not in the user's PATH.

Answer

The script must be owned by root.

Answer

The script does not have a shebang line (#!/bin/bash) at the top.

Question 10

An administrator wants to enforce that users in the 'contractors' group must change their password every 30 days, with a warning 7 days before expiry. Which command should be used?

Accepted Answer

chage -M 30 -W 7 contractors. None of the provided commands can be directly applied to a group. The `chage` command is the appropriate tool for password aging, but it requires a username as an argument. To enforce password aging on all users in the 'contractors' group, an administrator would need to iterate over each user in the group and run `chage -M 30 -W 7 <username>` for each.

Answer

groupmod -p 30 contractors

Answer

passwd -x 30 -w 7 contractors

Answer

usermod -e 30 contractors

Question 11

Match each Linux package management command to its distribution.

Accepted Answer

apt: Debian/Ubuntu. Package managers are tied to specific distribution families: apt (Debian/Ubuntu), yum (RHEL/CentOS 7), dnf (Fedora/RHEL 8+), pacman (Arch), and zypper (openSUSE). Common confusions arise from mixing these tools across distributions.

Answer

apt: Red Hat Enterprise Linux

Answer

yum: Debian

Question 12

After editing a service unit file, which command must be run for changes to take effect?

Accepted Answer

systemctl daemon-reload. When a service unit file is edited, systemd must be notified to reload its configuration from disk. The `systemctl daemon-reload` command instructs systemd to re-read all unit files, applying any changes to the unit definitions without requiring a full system reboot. This is necessary because systemd caches unit file contents in memory, and only a daemon-reload will update that cache.

Answer

systemctl restart <service>

Answer

systemctl reenable <service>

Answer

systemctl reload <service>

Question 13

A junior administrator needs to add user 'mchen' to the supplementary group 'developers' without removing existing group memberships. Which command should be used?

Accepted Answer

usermod -aG developers mchen. To add a user to a supplementary group while preserving existing memberships, use usermod with the -a (append) and -G (supplementary groups) options. Without -a, the -G option replaces all supplementary groups. This command safely adds the new group without affecting others, ensuring the user retains all necessary access.

Answer

usermod -G developers mchen

Answer

groupmod -a -U mchen developers

Answer

gpasswd -a mchen developers

Question 14

Which THREE commands can change the priority of an already running process?

Accepted Answer

top (press 'r'). Option B (top, press 'r') is correct because within the interactive top utility, pressing 'r' prompts for a PID and a new nice value, allowing you to renice an already running process on the fly. Option C (chrt) is correct because chrt sets or changes the scheduling policy and real-time priority of a running process by PID (e.g., chrt -p -f 10 ), directly altering its priority attributes. Option E (renice) is correct because renice is specifically designed to change the nice value of one or more running processes (renice -n 5 -p ), which adjusts their CPU scheduling priority. Option A (kill -STOP) is incorrect because it only suspends a process with SIGSTOP and does not modify its priority. Option D (nice) is incorrect because nice only launches a new command with a specified nice value; it cannot change the priority of an already running process.

Answer

kill -STOP

Answer

nice

Question 15

A Linux server is unable to resolve the hostname 'app.internal.example.com' but can resolve other names. The /etc/nsswitch.conf file contains: hosts: files mdns4_minimal [NOTFOUND=return] dns. The /etc/hosts file does not list the hostname. Which configuration change would most likely resolve the issue?

Accepted Answer

Remove the mdns4_minimal entry or change it to 'mdns4' without the NOTFOUND=return. The issue is that mdns4_minimal with [NOTFOUND=return] causes the resolver to stop after a failed mDNS query, preventing it from falling back to DNS. Since the hostname is not in /etc/hosts and not reachable via mDNS, the resolver returns 'not found' immediately without querying DNS. Removing the mdns4_minimal entry or changing it to 'mdns4' (without the NOTFOUND=return) allows the resolver to proceed to DNS if mDNS fails.

Answer

Change the hosts line to: hosts: dns files mdns4_minimal

Answer

Configure /etc/resolv.conf to use a different DNS server

Answer

Add the hostname to the local multicast DNS configuration