LFCS Practice Exam 3 — 20 Questions

Question 1

A system administrator needs to mount an ext4 filesystem with the options 'noatime' and 'errors=remount-ro'. Which mount command is correct?

Accepted Answer

mount -o noatime,errors=remount-ro /dev/sda1 /mnt. The `mount -o noatime,errors=remount-ro /dev/sda1 /mnt` command uses a single `-o` flag with a comma-separated list of mount options, which is the proper syntax for specifying multiple options. The `noatime` option disables updating the access time on reads, and `errors=remount-ro` tells the kernel to remount the filesystem as read-only if an I/O error is encountered, both of which are valid ext4 mount options.

Answer

mount -o noatime,errors=remount /dev/sda1 /mnt

Answer

mount -o noatime -o errors=remount-ro /dev/sda1 /mnt

Answer

mount -o atime=no,errors=remount-ro /dev/sda1 /mnt

Question 2

Which THREE of the following statements about the user private group (UPG) scheme are true?

Accepted Answer

It is the default scheme in Red Hat-based distributions.. Options A, D, and E are true. A: It is the default scheme in Red Hat-based distributions. D: It ensures that new files have a default group of the user's private group. E: Each user is assigned a unique group with the same name as the username. B is false because umask 0027 gives group read permission, not denies it. C is false because the primary group is the user's private group, not a system group.

Answer

The umask 0027 ensures files created are NOT readable by the group.

Answer

The primary group of a user is a system group with GID less than 1000.

Question 3

Which command displays the UUID of all filesystems on the system?

Accepted Answer

lsblk -f. The `lsblk -f` command lists all block devices and includes the filesystem type and UUID for each filesystem, making it the correct choice for displaying UUIDs of all filesystems on the system. The `-f` option specifically adds filesystem information, including UUIDs, to the output.

Answer

blkid

Answer

df -h

Answer

fdisk -l

Question 4

A server has two network interfaces: eth0 (public IP 203.0.113.10/24) and eth1 (private IP 10.0.0.1/8). The default gateway is 203.0.113.1. The admin wants to ensure that traffic to the private subnet 10.0.0.0/8 goes via eth1. Which command correctly adds a static route?

Accepted Answer

ip route add 10.0.0.0/8 dev eth1. It adds a static route for the 10.0.0.0/8 network directly via the eth1 interface, which is the private interface with IP 10.0.0.1/8. The `ip route add` command with `dev eth1` specifies that traffic destined for the 10.0.0.0/8 subnet should be sent out through eth1, without needing a next-hop gateway since eth1 is directly connected to that subnet.

Answer

ip route add 10.0.0.1/8 dev eth1

Answer

ip route add 10.0.0.0/8 via 10.0.0.1 dev eth0

Answer

route add -net 10.0.0.0/8 eth1

Question 5

Order the steps to mount an ext4 filesystem from an external USB drive automatically at boot.

Accepted Answer

Identify the UUID using blkid, create the mount point directory, add an entry to /etc/fstab using the UUID with options defaults and dump/pass values, then run mount -a to test.. Using UUID in fstab ensures persistent mounting; testing with mount -a verifies no errors.

Answer

Plug in the USB drive, create the mount point, add an entry to /etc/fstab using the device name (e.g., /dev/sdb1), then reboot without testing.

Answer

Run mount -a first, then edit /etc/fstab to add the entry using UUID, and finally create the mount point.

Answer

Add an entry to /etc/fstab using the device name, manually mount with mount command, then create the mount point after mounting.

Question 6

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 7

A system administrator wants to limit the CPU usage of a service. Which systemd resource control directive should be used?

Accepted Answer

CPUAccounting=yes and CPUQuota. To limit CPU usage in systemd, you must first enable CPU accounting with `CPUAccounting=yes` to track CPU consumption, and then set `CPUQuota` to specify a maximum percentage of CPU time the service can use. Without `CPUAccounting=yes`, the `CPUQuota` directive is ignored by systemd, making the combination essential for enforcing a hard CPU limit.

Answer

CPUShares

Answer

CPUQuota

Answer

CPULimit

Question 8

Which THREE of the following commands can be used to view the contents of a compressed file named 'file.gz' without permanently decompressing it? (Choose exactly three.)

Accepted Answer

zmore file.gz. `zmore` is a utility that allows you to view the contents of a compressed file (such as `file.gz`) page by page without permanently decompressing it. It internally decompresses the file on the fly and pipes the output through `more`, making it ideal for inspecting large compressed files without modifying the original archive.

Answer

gzip file.gz

Answer

gunzip file.gz

Question 9

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 10

Which THREE steps are required to create a new ext4 filesystem on /dev/sdc1 and ensure it is automatically mounted at /mnt/data at boot? (Choose three.)

Accepted Answer

mkfs.ext4 /dev/sdc1. B is correct because `mkfs.ext4 /dev/sdc1` creates a new ext4 filesystem on the specified partition. This is the fundamental step to format the device with the ext4 filesystem type, which is required before the partition can be mounted and used for data storage.

Answer

e2label /dev/sdc1 data

Answer

mount /dev/sdc1 /mnt/data

Question 11

An administrator created a new user 'john' with the default settings, but 'john' cannot log in. The error message indicates an invalid shell. Which command should the administrator use to fix this issue?

Accepted Answer

usermod -s /bin/bash john. The correct command is `usermod -s /bin/bash john` because it modifies an existing user's login shell in the `/etc/passwd` file. The error 'invalid shell' indicates the user's current shell is either missing or not listed in `/etc/shells`, and `usermod` is the proper tool to change a user's attributes after account creation.

Answer

passwd -s john

Answer

useradd -s /bin/bash john

Answer

chsh -s /bin/bash john

Question 12

An administrator created an LVM snapshot of a logical volume to perform a backup. During the backup, the snapshot runs out of space. What will happen to the original logical volume?

Accepted Answer

The snapshot becomes invalid and must be recreated.. When an LVM snapshot runs out of space, it becomes invalid and cannot track changes made to the original logical volume during the backup. The snapshot is automatically dropped by the device-mapper, and any attempt to mount or read it will fail. The original logical volume remains fully functional and unaffected, but the snapshot must be recreated to perform a new backup.

Answer

The original volume becomes read-only.

Answer

The backup completes successfully but data may be inconsistent.

Answer

The original volume is automatically extended.

Question 13

A system administrator wants to view the last 10 lines of the system log file '/var/log/syslog' and continue to watch for new lines as they are appended. Which command should be used?

Accepted Answer

tail -n 10 -f /var/log/syslog. The `tail -n 10 -f /var/log/syslog` command first displays the last 10 lines of the file and then uses the `-f` (follow) flag to continuously monitor the file for new appended lines, outputting them in real time. This matches the requirement to both view the last 10 lines and watch for new entries.

Answer

tail -n 10 /var/log/syslog

Answer

less /var/log/syslog

Answer

head -n 10 /var/log/syslog

Question 14

A Linux system reports 'Out of memory' errors frequently. The administrator checks memory usage with 'free -m' and notices that most memory is used by file cache. Which command can the administrator run to immediately free up the cache without affecting running processes?

Accepted Answer

sysctl vm.drop_caches=1. Both options A and C are correct methods to free pagecache (file cache) without terminating processes. Writing to /proc/sys/vm/drop_caches via echo or using the sysctl command achieve the same result. The administrator can use either command to immediately reclaim memory used by file cache. Option B disables swap but does not free cache, and option D kills a process unnecessarily.

Answer

swapoff -a

Answer

kill -9 $(pidof some_process)

Question 15

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

Accepted Answer

/home. (/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 16

Which THREE commands can show the current system time and date?

Accepted Answer

timedatectl. B is correct because `timedatectl` is the primary command in systemd-based Linux distributions (e.g., RHEL 7+, Ubuntu 16.04+) for querying and configuring system time, date, time zone, and NTP synchronization. It displays the current local time, UTC time, RTC time, and time zone status in a structured output.

Answer

time

Answer

ntpdate

Question 17

A server with two network interfaces (eth0 and eth1) needs to be configured as a bridge (br0) to allow KVM virtual machines to share the host's physical network. Which steps are correct?

Accepted Answer

Create bridge br0, add eth0 as port, assign IP to br0, remove IP from eth0.. Bridging requires the physical interface (eth0) to be added as a port to the bridge (br0) without an IP address, while the bridge itself gets the IP address to act as the network layer endpoint. This allows KVM virtual machines connected to br0 to communicate through eth0, which operates at layer 2. Removing the IP from eth0 prevents IP conflicts and ensures all traffic is handled by the bridge.

Answer

Create bridge br0, add eth0 as port, assign IP to eth0, do not assign IP to br0.

Answer

Create bond0 from eth0 and eth1, then add bond0 to bridge br0.

Answer

Create bridge br0, add eth0 and eth1 as bridge ports, assign IP to br0, remove IP from eth0 and eth1.

Question 18

A company follows the principle of least privilege. Several developers need sudo access to run specific commands like systemctl and journalctl. What is the best practice for granting this access?

Accepted Answer

Create a new group 'devops', add developers to it, and create a sudoers drop-in file with rules for specific commands. It follows the principle of least privilege by creating a dedicated 'devops' group and using a sudoers drop-in file (e.g., /etc/sudoers.d/devops) to grant only specific commands like systemctl and journalctl. This avoids modifying the main /etc/sudoers file directly, which is error-prone, and ensures that developers have no more privileges than necessary. The drop-in file approach is the recommended best practice for maintainability and security.

Answer

Use 'usermod -a -G sudo' for each developer and edit /etc/sudoers manually with visudo

Answer

Add all developers to the 'wheel' group and configure %wheel ALL=(ALL) ALL

Answer

Edit /etc/sudoers directly to add each developer username with command restrictions

Question 19

You are a systems administrator for a company that runs a critical web application on a Linux server. The server has two network interfaces: eth0 (public IP 203.0.113.10/24, gateway 203.0.113.1) and eth1 (private IP 10.0.0.10/24). The web server listens on port 443 (HTTPS) and must be accessible from the internet. The server also needs to connect to an internal database server at 10.0.0.50/24 on port 3306. Recently, users reported that the website is intermittently unreachable. You SSH into the server and run 'ss -tln' and see that the web server is listening on 0.0.0.0:443. You check the routing table with 'ip route show' and see: default via 203.0.113.1 dev eth0; 10.0.0.0/24 dev eth1 proto kernel scope link src 10.0.0.10. You also run 'iptables -L -n -v' and see: Chain INPUT (policy ACCEPT), with no rules. However, you notice that the server's default gateway is unreachable from the server itself when you run 'ping 203.0.113.1' (100% packet loss). What is the most likely cause of the intermittent unreachability?

Accepted Answer

The default gateway is unreachable, preventing return traffic from the internet.. The server's default gateway (203.0.113.1) is unreachable, as confirmed by the 100% packet loss on ping. This means that although the web server is listening on 0.0.0.0:443 and the firewall allows traffic, any response packets from the server to internet clients must be routed through the default gateway. Without a working gateway, return traffic cannot reach the clients, causing intermittent unreachability from the internet.

Answer

The web server is not listening on the public IP address.

Answer

A firewall rule is blocking incoming HTTPS traffic.

Answer

The private interface eth1 has a misconfigured IP address.

Question 20

Given the routing table output in the exhibit, what will happen when the system tries to send a packet to 10.1.1.1?

Accepted Answer

The packet is sent to 192.168.1.1 via eth0.. The routing table shows a specific route for the 10.0.0.0/8 network via gateway 192.168.1.1 on eth0. Since 10.1.1.1 falls within this subnet, the packet is forwarded to 192.168.1.1 via eth0, not through the default route or any other interface.

Answer

The packet is sent via eth1.

Answer

The packet is sent via default route.

Answer

The packet is dropped because there is no subnet matching 10.1.1.1.