LFCS Practice Test 24 — 15 Questions

Question 1

Which command displays the listening UDP ports on a Linux system?

Accepted Answer

ss -uln. `ss -uln` specifically displays listening UDP sockets. The `-u` flag filters for UDP, `-l` shows only listening sockets, and `-n` displays numeric addresses and ports (avoiding DNS resolution). This is the most precise command for listing listening UDP ports.

Answer

ss -a

Answer

ss -tln

Answer

netstat -tln

Question 2

An administrator configures a systemd service with Restart=on-failure and RestartSec=10. What happens if the service exits with a non-zero exit code?

Accepted Answer

It waits 10 seconds before restarting. When Restart=on-failure is set, systemd only restarts the service if it exits with a non-zero exit code or is terminated by a signal (excluding SIGHUP, SIGINT, SIGTERM, and SIGPIPE). The RestartSec=10 directive then introduces a 10-second delay before the restart attempt, preventing rapid restart loops and giving the system time to stabilize.

Answer

It restarts immediately

Answer

It retries infinitely regardless of exit code

Answer

It does not restart

Question 3

An administrator needs to set the reserved block percentage on an ext4 filesystem to 1% for a non-root filesystem. Which command accomplishes this?

Accepted Answer

tune2fs -m 1 /dev/sdb1. The `tune2fs -m` command sets the reserved block percentage for an ext4 filesystem, and `-m 1` sets it to exactly 1%. This is the standard way to adjust reserved space on a non-root ext4 filesystem, as root filesystems typically have a default of 5% reserved for system processes.

Answer

tune2fs -m 0.5 /dev/sdb1

Answer

tune2fs -r 1% /dev/sdb1

Answer

tune2fs -c 1 /dev/sdb1

Question 4

A system administrator needs to configure a static IP address on a CentOS 7 server. Which file should be edited to set the IP address permanently?

Accepted Answer

/etc/sysconfig/network-scripts/ifcfg-eth0. On CentOS 7, network interfaces are configured via scripts located in /etc/sysconfig/network-scripts/, with each interface having a file named ifcfg-<interface>. The ifcfg-eth0 file stores static IP settings such as IPADDR, NETMASK, and GATEWAY, which are read by the network service (network.service) to apply persistent configuration.

Answer

/etc/netplan/01-netcfg.yaml

Answer

/etc/network/interfaces

Answer

/etc/hostname

Question 5

A system administrator needs to check the current CPU load and memory usage on a Linux server. Which command should be used to display a dynamic, real-time view of running processes and system resource utilization?

Accepted Answer

top. (top) is correct because it provides a dynamic, real-time view of running processes and system resource utilization, including CPU load, memory usage, and process details. It updates continuously by default, making it ideal for monitoring live system performance.

Answer

uptime

Answer

ps aux

Answer

free -h

Question 6

A system administrator notices that a process is consuming 100% CPU and is unresponsive. Which command should be used to immediately stop the process if the PID is 2345?

Accepted Answer

kill -9 2345. `kill -9 2345` sends the SIGKILL signal (signal 9) to process ID 2345, which immediately terminates the process without allowing it to clean up or ignore the signal. This is the appropriate action for an unresponsive process consuming 100% CPU, as SIGKILL cannot be caught or blocked by the process.

Answer

pkill -9 processname

Answer

systemctl stop processname

Answer

kill -15 2345

Question 7

Which TWO commands can be used to view the last 10 lines of a file and also follow new lines as they are written?

Accepted Answer

tail -f -n 10. Option A, `tail -f -n 10`, is correct because `-n 10` displays the last 10 lines of the file and `-f` (follow) keeps the file open and prints new lines as they are appended, which is exactly the requested behavior. Option E, `less +F`, is correct because the `+F` command starts `less` in follow mode, initially showing the file content (including the tail end) and continuously displaying newly appended lines, similar to `tail -f`. Option B, `cat -n`, only concatenates the file with line numbers and does not follow new lines. Option C, `tail -n 10`, shows the last 10 lines but lacks the follow capability. Option D, `head -n 10`, shows the first 10 lines and does not follow the file.

Answer

cat -n

Answer

tail -n 10

Answer

head -n 10

Question 8

Scenario: You are managing a Linux server that hosts a web application. The application runs under the user 'webapp' and the group 'webgroup'. Recently, a new intern 'john' (username 'john') needs to be able to view and modify files in /var/www/html, which is owned by root:webgroup with permissions 775. John is currently a member of the group 'staff', but not 'webgroup'. The security policy requires that John must be able to edit files without using sudo, and his primary group must remain 'staff'. Which of the following actions should you take to meet the requirements?

Accepted Answer

Add John to the 'webgroup' supplementary group with 'usermod -a -G webgroup john'.. Adding John to the 'webgroup' supplementary group with `usermod -a -G webgroup john` grants him group-level access to /var/www/html (owned by root:webgroup with permissions 775) without changing his primary group 'staff'. This allows him to view and modify files as a member of 'webgroup', satisfying the security policy that he must not use sudo and his primary group must remain unchanged.

Answer

Change the group ownership of /var/www/html to 'staff' and set the setgid bit.

Answer

Change John's primary group to 'webgroup' with 'usermod -g webgroup john'.

Answer

Set the setgid bit on /var/www/html with 'chmod g+s /var/www/html'.

Question 9

An administrator is troubleshooting DNS resolution and wants to query the SOA record for a domain. Which three commands can be used? (Choose three.)

Accepted Answer

nslookup -type=soa example.com. The `nslookup -type=soa` command queries the DNS for the Start of Authority (SOA) record of a domain. The `-type=soa` flag explicitly sets the query type to SOA, which returns authoritative information about the zone, including the primary name server and administrator email.

Answer

nmcli dev show

Answer

getent hosts example.com

Question 10

Existing user 'jdoe' is a member of groups 'users' (primary) and 'staff'. The administrator needs to add 'jdoe' to group 'projectx' while preserving existing supplementary group memberships. Which command achieves this?

Accepted Answer

usermod -a -G projectx jdoe. The `-a` (append) flag combined with `-G` (supplementary groups) adds the user to the specified group without removing existing supplementary group memberships. Without `-a`, the `-G` flag replaces all supplementary groups with the listed ones, which would remove the 'staff' group membership.

Answer

usermod -g projectx -G projectx jdoe

Answer

usermod -g projectx jdoe

Answer

usermod -G projectx jdoe

Question 11

A system administrator needs to find all files in /var/log that have been modified in the last 7 days. Which command accomplishes this?

Accepted Answer

find /var/log -type f -mtime -7. The `find` command with `-mtime -7` searches for files whose modification time (content change) is less than 7 days ago, which matches the requirement of 'modified in the last 7 days'. The `-type f` restricts the search to regular files, and `/var/log` is the target directory.

Answer

find /var/log -type f -atime -7

Answer

find /var/log -type f -ctime -7

Answer

find /var/log -type f -mtime +7

Question 12

A system administrator notices that a web server is not reachable from the internet but is reachable from the internal network. The server's IP is 10.0.1.10/24, and the gateway is 10.0.1.1. Which command should be used to verify the default gateway configuration?

Accepted Answer

ip route show. The `ip route show` command displays the kernel routing table, including the default gateway entry. Since the server is reachable internally but not from the internet, a missing or incorrect default gateway is the likely cause. This command directly verifies whether a default route (e.g., via 10.0.1.1) is present.

Answer

arp -a

Answer

ip addr show

Answer

ss -tln

Question 13

Which command adds an existing user to a supplementary group without removing the user from other groups?

Accepted Answer

usermod -aG groupname username. The correct command is `usermod -aG groupname username`. The `-a` option (append) combined with `-G` (supplementary groups) adds the user to the specified group without affecting existing supplementary group memberships. Option A (`groupmod -a`) is incorrect because `groupmod` modifies group attributes, not user membership. Option B (`-A`) is not a valid `usermod` option. Option D (`-g`) changes the user's primary group, not supplementary groups.

Answer

groupmod -a username groupname

Answer

usermod -A groupname username

Answer

usermod -g groupname username

Question 14

A service is configured to run as a specific user. Which directive in the [Service] section sets the user?

Accepted Answer

User. In systemd service units, the directive to specify the user under which the service process runs is `User=` within the `[Service]` section. This directive sets the Unix user account (by name or UID) that the service's main PID will execute as, ensuring proper privilege separation and security.

Answer

RunAs

Answer

Account

Answer

UserID

Question 15

A user wants to set the permissions of a file to 'rwxr-xr--'. Which octal permission value should they use with chmod?

Accepted Answer

754. The permissions 'rwxr-xr--' mean that the owner has read, write, and execute (rwx = 7), the group has read and execute (r-x = 5), and others have only read (r-- = 4). Therefore, the correct octal value is 754. Option A is correct. Option B (755) gives others execute, option C (644) gives owner no execute and group no execute, and option D (744) gives group no execute.

Answer

755

Answer

644

Answer

744