LFCS Practice Questions 1 — 50 Questions

Question 1

After deleting user 'alice', the system administrator wants to also remove the home directory and mail spool. Which command should be used?

Accepted Answer

userdel -r alice. The correct option is B, userdel -r alice. The -r flag removes the user's home directory and mail spool, along with the user account. This is the standard flag for removing user data along with the account.

Answer

userdel -Z alice

Answer

userdel -f alice

Answer

userdel --remove alice

Question 2

Which TWO commands can be used to resolve a hostname to an IP address?

Accepted Answer

host. The `host` command is a simple DNS lookup utility that queries DNS servers to resolve a hostname to an IP address. It directly performs forward DNS resolution using the system's configured resolvers and returns the A or AAAA record for the given name.

Answer

traceroute

Answer

ping

Answer

ifconfig

Question 3

A system administrator is managing a RHEL 8 server that requires a static IP address on interface ens192. The administrator modifies /etc/sysconfig/network-scripts/ifcfg-ens192 to set BOOTPROTO=static, IPADDR=192.168.1.100, PREFIX=24, GATEWAY=192.168.1.1, and DNS1=8.8.8.8. After saving, the administrator runs 'systemctl restart NetworkManager'. The interface obtains the correct static IP and network connectivity works. However, after a reboot of the server, the interface fails to come up with the static IP and instead obtains an IP via DHCP from the local network. The administrator verifies that the DHCP server is active and that the physical connection is good. What is the most likely cause of the issue?

Accepted Answer

The ONBOOT parameter is set to no or missing in the configuration file.. The ONBOOT parameter controls whether the interface is activated at system boot. If set to 'no' or missing entirely, NetworkManager will not bring up the interface automatically after a reboot, causing it to fall back to DHCP if a DHCP client is active. Setting BOOTPROTO=static and IPADDR correctly only takes effect when ONBOOT=yes is present.

Answer

The kernel parameter nomodeset is set in /etc/default/grub.

Answer

The firewall is blocking the static IP assignment.

Answer

The network service is not enabled to start at boot.

Question 4

Which TWO commands can be used to display listening TCP ports on a Linux system?

Accepted Answer

ss -tln. The `ss -tln` command displays listening TCP sockets by using the `-t` flag for TCP, `-l` for listening sockets, and `-n` to show numeric addresses and ports without resolving service names. It reads socket information directly from the kernel's netlink interface, making it the modern replacement for netstat on Linux systems.

Answer

nmap -sT localhost

Answer

iptables -L

Answer

lsof -i TCP

Question 5

A system administrator needs to list all files in the current directory, including hidden files, in a long listing format sorted by modification time (oldest first). Which command achieves this?

Accepted Answer

ls -lart. `ls -lart` combines the `-l` (long listing), `-a` (include hidden files starting with dot), `-r` (reverse order), and `-t` (sort by modification time, newest first). The reverse flag flips the sort to oldest first, meeting the requirement exactly.

Answer

ls -lihrt

Answer

ls -lat

Answer

ls -lrt

Question 6

An administrator wants to ensure that a service is listening on TCP port 8080 and accessible from remote hosts. Which command will confirm that the service is listening on the correct interface?

Accepted Answer

ss -tlnp. The `ss -tlnp` command displays listening (`-l`) TCP (`-t`) sockets with numeric addresses (`-n`) and the associated process (`-p`), which directly confirms that a service is bound to TCP port 8080 on a specific interface (e.g., 0.0.0.0:8080 or 192.168.1.10:8080). This ensures the service is listening on the correct interface and is reachable from remote hosts.

Answer

iptables -L

Answer

netstat -i

Answer

ip addr

Question 7

A user reports that a script fails with 'Permission denied' when executed. The script has permissions -rw-r--r-- and is owned by the user. Which command should the user run to make the script executable for the owner only?

Accepted Answer

chmod u+x script.sh. The script currently has permissions `-rw-r--r--`, meaning the owner has read and write but not execute permission. The `chmod u+x` command adds the execute permission for the owner only, which is exactly what the user needs to run the script without affecting group or others.

Answer

chmod u+s script.sh

Answer

chown :users script.sh

Answer

chmod +x script.sh

Question 8

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 9

Which TWO methods can be used to set a static IPv4 address on a CentOS 7 system? (Choose two.)

Accepted Answer

Use the nmtui utility. Nmtui is a text-based user interface for NetworkManager, which is the default networking service on CentOS 7. It allows you to interactively configure network interfaces, including setting a static IPv4 address, without needing to manually edit configuration files. Option E is correct because the ifcfg-eth0 file in /etc/sysconfig/network-scripts is the traditional, direct configuration method for network interfaces on CentOS 7, where you can set BOOTPROTO=static and define IPADDR, PREFIX, and GATEWAY.

Answer

Run the command 'systemctl set-static-ip eth0 192.168.1.100/24'

Answer

Use 'ip addr add 192.168.1.100/24 dev eth0'

Answer

Edit the /etc/network/interfaces file

Question 10

Which TWO of the following commands can be used to check and repair an ext4 filesystem?

Accepted Answer

fsck.ext4 /dev/sdb1. Option A, fsck.ext4 /dev/sdb1, is correct because fsck.ext4 is the ext4-specific front-end of the fsck utility, which checks and repairs ext4 filesystems on the specified block device. Option D, e2fsck /dev/sdb1, is also correct because e2fsck is the underlying ext2/ext3/ext4 filesystem checker that fsck.ext4 invokes, and it can both verify and repair ext4 filesystems. Option B, xfs_repair, is wrong because it is the repair tool for XFS filesystems, not ext4. Option C, mkfs.ext4, is wrong because it creates (formats) a new ext4 filesystem rather than checking or repairing an existing one. Option E, btrfs check, is wrong because it is used to check Btrfs filesystems, not ext4.

Answer

xfs_repair /dev/sdb1

Answer

mkfs.ext4 /dev/sdb1

Answer

btrfs check /dev/sdb1

Question 11

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 12

A system administrator needs to ensure that a Linux server can communicate with other hosts on the same subnet. Which command should be used to verify the IP address and netmask configuration?

Accepted Answer

ip addr show. The `ip addr show` command is the modern, recommended tool in Linux for viewing IP addresses and netmasks (prefix lengths) assigned to network interfaces. It directly displays the configuration needed to verify subnet communication, unlike legacy tools that may not show the netmask clearly or mix routing information.

Answer

netstat -rn

Answer

route -n

Answer

ifconfig

Question 13

A user reports that they cannot reach a remote server by hostname but can reach it by IP address. Which configuration file is most likely misconfigured?

Accepted Answer

/etc/resolv.conf. The /etc/resolv.conf file configures the system's DNS resolver, specifying the nameservers to query for hostname-to-IP resolution. If a user can reach a server by IP but not by hostname, it indicates that DNS resolution is failing, which is most commonly due to a missing or incorrect nameserver entry in /etc/resolv.conf.

Answer

/etc/sysconfig/network

Answer

/etc/hosts

Answer

/etc/nsswitch.conf

Question 14

A system administrator needs to schedule a one-time task that will run at 2:30 AM on July 15. Which command should be used to create this job?

Accepted Answer

at 2:30 AM July 15. The at command is specifically designed for scheduling one-time tasks at a precise date and time. Using at 2:30 AM July 15 allows the administrator to queue a command that will execute once at that moment, fulfilling the requirement.

Answer

crontab -e

Answer

systemd-run --on-calendar="*-07-15 02:30:00"

Answer

batch

Question 15

An administrator needs to compress a directory named 'project' into a tarball with maximum compression using gzip. Which command is appropriate?

Accepted Answer

tar -czvf archive.tar.gz project. The `-z` flag tells tar to compress the archive using gzip. The `-c` flag creates a new archive, `-v` provides verbose output, and `-f` specifies the archive filename. The `.tar.gz` extension is the conventional extension for a gzip-compressed tarball. Although other tools like bzip2 or xz can achieve higher compression ratios, the question explicitly asks for using gzip.

Answer

tar -cjvf archive.tar.bz2 project

Answer

tar -cJvf archive.tar.xz project

Answer

tar -cvf archive.tar project

Question 16

An administrator is configuring a bridge using iproute2. Which command correctly attaches eth0 to bridge br0?

Accepted Answer

ip link set eth0 master br0. The `ip link set eth0 master br0` command attaches the physical interface `eth0` as a slave port of the bridge `br0` using the iproute2 suite. The `master` keyword specifies the bridge device that should become the master of the specified interface, which is the standard way to add an interface to a bridge with iproute2.

Answer

ip link set br0 master eth0

Answer

nmcli device modify eth0 master br0

Answer

brctl addif br0 eth0

Question 17

A security policy requires that all users in the 'admin' group must have a umask of 027 set automatically upon login. An administrator adds 'umask 027' to /etc/profile. However, users report that the umask is still 022. What is a likely cause?

Accepted Answer

The umask in /etc/profile is overridden by user-specific .bash_profile or .bashrc files.. User-specific shell configuration files (like ~/.bash_profile, ~/.bash_login, or ~/.profile for login shells, and ~/.bashrc for interactive non-login shells) are sourced after /etc/profile. These files can override the system-wide umask setting with a user-defined value, such as the default 022. Since the administrator only modified /etc/profile, any existing user-specific umask command in their personal dotfiles will take precedence.

Answer

The umask command in /etc/profile has a syntax error that is silently ignored.

Answer

The admin placed the umask command after the call to /etc/bash.bashrc which resets it.

Answer

The admin forgot to run 'source /etc/profile' on each user's session.

Question 18

A systems administrator needs to add a new user 'jdoe' with a home directory in /export/home, a UID of 1500, and an expiry date of 2025-12-31. Which command should they use?

Accepted Answer

useradd -u 1500 -d /export/home/jdoe -e 2025-12-31 jdoe. The `useradd` command with `-u 1500` sets the UID, `-d /export/home/jdoe` explicitly specifies the home directory path (without creating it unless `-m` is also used), and `-e 2025-12-31` sets the account expiry date in YYYY-MM-DD format. This matches all requirements: UID 1500, home directory at /export/home/jdoe, and expiry on 2025-12-31.

Answer

useradd -u 1500 -d /export/home/jdoe -c 2025-12-31 jdoe

Answer

useradd -u 1500 -m -e 2025-12-31 jdoe

Answer

useradd -u 1500 -b /export/home -e 2025-12-31 jdoe

Question 19

You administer a Linux server that acts as a network gateway. It has two network interfaces: eth0 (external, with IP 203.0.113.10/24, gateway 203.0.113.1) and eth1 (internal, with IP 192.168.1.1/24). The server is running firewalld and has IP forwarding enabled. Internal hosts (192.168.1.0/24) can access the internet through NAT, which is configured using firewalld's masquerade on the external zone. However, you need to allow a specific internal server (192.168.1.100) to be reachable from the internet on TCP port 443 (HTTPS). You add a port forwarding rule using firewall-cmd: 'firewall-cmd --zone=external --add-forward-port=port=443:proto=tcp:toport=443:toaddr=192.168.1.100'. After reloading the firewall, external users still cannot connect to 203.0.113.10:443. You verify that the internal server is running HTTPS and that its local firewall allows port 443. What is the most likely reason the port forwarding is not working?

Accepted Answer

The rule needs to include masquerade for the destination address; use a rich rule with 'masquerade'.. A simple port forward rule in firewalld does not automatically rewrite the source IP address for return traffic. Without masquerade on the forwarded traffic, the internal server sees the original external source IP and sends its response directly to that IP, bypassing the gateway. Adding a rich rule with 'masquerade' for the destination address ensures that the gateway performs SNAT on the forwarded packets, so the internal server sees the gateway as the source and returns traffic through it.

Answer

The port forwarding rule should be added to the internal zone instead of the external zone.

Answer

The internal server has a different default gateway.

Answer

IP forwarding is not enabled on the system.

Question 20

An administrator wants to ensure that a service starts automatically after a system crash. Which systemd command should be used?

Accepted Answer

systemctl enable service. The `systemctl enable service` command creates the necessary symlinks in the systemd unit configuration directories (e.g., `/etc/systemd/system/multi-user.target.wants/`) so that the service is automatically started at boot. This includes recovery after a system crash, because the crash triggers a reboot, and the enabled service will be started as part of the normal boot process.

Answer

systemctl daemon-reload

Answer

systemctl mask service

Answer

systemctl start service