LFCS Practice Test 5 — 10 Questions

Question 1

A financial firm requires all internal SSH connections to be encrypted with at least 256-bit ciphers. An administrator is configuring the SSH server. Which configuration line should be added to /etc/ssh/sshd_config?

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

Accepted Answer

Ciphers aes256-ctr. The Ciphers directive in sshd_config explicitly controls the symmetric encryption algorithms used to encrypt SSH session data. The cipher aes256-ctr provides 256-bit encryption, meeting the firm's requirement for at least 256-bit ciphers. Other directives like MACs, KexAlgorithms, or HostKeyAlgorithms do not directly set the encryption cipher strength.

Answer

MACs hmac-sha2-256

Answer

KexAlgorithms diffie-hellman-group-exchange-sha256

Answer

HostKeyAlgorithms ssh-rsa

Question 2

Which TWO of the following are valid ways to mount a filesystem with the 'noexec' option to prevent execution of binaries?

Accepted Answer

mount -o noexec /dev/sdb1 /mnt/data. Option A is correct because the mount command's -o flag accepts the noexec mount option directly, so 'mount -o noexec /dev/sdb1 /mnt/data' mounts the device /dev/sdb1 at /mnt/data with binary execution disabled. Option E is correct because the fourth field of an /etc/fstab entry holds the mount options, so adding 'noexec' there (e.g., 'defaults,noexec') makes the filesystem mount with noexec persistently at boot or on 'mount -a'. Option B is wrong because 'exec' is the opposite of noexec and explicitly permits execution. Option C is wrong because 'defaults' expands to rw,suid,dev,exec,auto,nouser,async, which includes exec and thus allows binaries to run. Option D is wrong because 'mount --bind' merely mirrors one directory tree onto another and does not itself set the noexec option.

Answer

Add 'exec' to the fourth field of /etc/fstab for the entry.

Answer

Add 'defaults' to the fourth field of /etc/fstab for the entry.

Answer

mount --bind /mnt/data1 /mnt/data2

Question 3

An administrator is troubleshooting a server that runs a critical application. The server has 16 GB of RAM and 8 CPU cores. The administrator notices that the server becomes very slow during peak hours. Analysis of 'iostat -x 1' shows that the average wait time (await) for the main disk (sda) is consistently above 1000 ms, while the average service time (svctm) is around 5 ms. What is the most likely cause?

Accepted Answer

There is a large queue of I/O requests waiting to be serviced.. The 'await' value in iostat represents the average time (in milliseconds) for I/O requests to be serviced, including time spent waiting in the queue. With 'await' at 1000+ ms and 'svctm' at only 5 ms, the vast majority of the time is spent waiting, not being serviced. This indicates a large queue of pending I/O requests, which is the direct cause of the slowdown.

Answer

The CPU is overloaded, causing processes to wait for CPU time.

Answer

The system is using swap space heavily, causing disk I/O.

Answer

The disk is experiencing hardware errors.

Question 4

A system administrator needs to ensure the Apache httpd service starts automatically on system boot. Which command should they use?

Accepted Answer

systemctl enable httpd. The `systemctl enable httpd` command creates the necessary symlinks in the systemd unit configuration directories (typically `/etc/systemd/system/multi-user.target.wants/`) to ensure the Apache httpd service starts automatically at boot time. This is the correct approach because `enable` configures the service to be started on system startup, whereas `start` only runs it immediately without affecting boot behavior.

Answer

systemctl start httpd

Answer

systemctl disable httpd

Answer

systemctl reload httpd

Question 5

Refer to the exhibit. The output of 'ps aux' shows a process named 'process_hog' with PID 1234 consuming 99.5% CPU. The process is stuck in an infinite loop and does not respond to SIGTERM. Which signal should be used to forcefully terminate it?

Accepted Answer

kill -9 1234. SIGKILL (signal 9) cannot be caught, blocked, or ignored by a process, making it the only reliable way to terminate a process that is stuck in an infinite loop and unresponsive to SIGTERM. Since the process does not respond to SIGTERM (signal 15), a forceful kill with kill -9 is necessary.

Answer

kill -2 1234

Answer

kill -15 1234

Answer

kill -19 1234

Question 6

You are managing a Linux server that hosts a critical web application. The server is running low on disk space in the root filesystem, and you need to free up space urgently. You run 'df -h' and see that /dev/sda1 is mounted on / and is 95% full. You also notice that /var/log/messages is over 2 GB in size. The application writes logs to /var/log/app.log, which is also large. The server has a separate /var partition that has plenty of free space. The application must continue running with minimal downtime. You need to compress and rotate logs without losing any data, and ensure that the root filesystem has at least 10% free space. Which of the following actions should you take first to achieve this goal?

Accepted Answer

Use logrotate with the 'copytruncate' option to rotate /var/log/app.log and move the rotated file to /var/old_logs/.. Logrotate with the 'copytruncate' option allows the application to continue writing to the same file descriptor while the current log is copied and then truncated to zero length. This avoids any application downtime and the rotated log can be moved to the separate /var partition (which has free space) for compression or archiving, freeing space on the root filesystem without data loss.

Answer

Delete /var/log/app.log and /var/log/messages to free space quickly.

Answer

Stop the application, truncate /var/log/app.log, then restart the application.

Answer

Compress /var/log/app.log using gzip and keep it in place.

Question 7

A system administrator needs to create a shared group 'projectx' and add existing users 'bob' and 'carol' to it. The users need to collaborate on files in a directory /projectx. What is the correct sequence of commands to set up the group and ensure new files created in /projectx are automatically owned by the group 'projectx'?

Accepted Answer

groupadd projectx; usermod -aG projectx bob; usermod -aG projectx carol; chmod g+s /projectx. It uses `groupadd` to create the group, `usermod -aG` to append users to the group without removing them from other groups, and `chmod g+s` to set the setgid bit on the directory. The setgid bit ensures that new files created in /projectx inherit the group ownership of the directory (projectx), enabling collaboration.

Answer

groupadd projectx; usermod -G projectx bob carol; chmod 2770 /projectx

Answer

addgroup projectx; adduser bob projectx; adduser carol projectx; chmod u+s /projectx

Answer

groupadd projectx; usermod -G projectx bob; usermod -G projectx carol; chmod g+s /projectx

Question 8

A systemd-networkd managed interface enp1s0 needs to be configured with a static IP address 192.168.1.100/24 and a default gateway via 192.168.1.1. Which .network file configuration is correct?

Accepted Answer

[Match]
Name=enp1s0
[Network]
Address=192.168.1.100/24
Gateway=192.168.1.1. Systemd-networkd uses the `[Match]` section with `Name=` to match the interface, and the `[Network]` section with `Address=` to assign a static IP address and `Gateway=` to set the default gateway. The syntax `Address=192.168.1.100/24` is the proper directive for defining a static IP address in a .network file, and `Gateway=192.168.1.1` correctly specifies the default gateway.

Answer

[Match]
Interface=enp1s0
[Network]
StaticIP=192.168.1.100/24
Gateway=192.168.1.1

Answer

[Link]
Name=enp1s0
[Network]
IPAddress=192.168.1.100/24
Gateway=192.168.1.1

Answer

[Match]
Name=enp1s0
[Network]
Address=192.168.1.100/24
DefaultGateway=192.168.1.1

Question 9

Which file stores the encrypted password (or password hash) for user accounts?

Accepted Answer

/etc/shadow. /etc/shadow is correct because it stores encrypted password hashes for user accounts, along with password aging information. It is readable only by root to prevent unauthorized access to password hashes. The /etc/passwd file historically stored passwords but now only contains user account information, with the password field replaced by an 'x' indicating the hash is in /etc/shadow.

Answer

/etc/group

Answer

/etc/passwd

Answer

/etc/gshadow

Question 10

A user wants to find all files in /var/log that have been modified within the last 2 days. Which command should they use?

Accepted Answer

find /var/log -mtime -2. The `find` command with `-mtime -2` searches for files whose content was last modified less than 2 days ago (i.e., within the last 48 hours). The minus sign before the number indicates 'less than' or 'within the last N days', which matches the user's requirement to find files modified within the last 2 days.

Answer

find /var/log -mmin -2880

Answer

find /var/log -mtime +2

Answer

find /var/log -mtime 2