010-160 The Linux Operating System — 20 Questions

Question 1

You are configuring a Linux server and need to determine which hard drive partition is currently mounted as the root filesystem. Which file should you inspect?

Accepted Answer

/etc/fstab. The /etc/fstab file is the system's static filesystem table, which lists all filesystems and their mount points, including the root filesystem. By inspecting /etc/fstab, you can see which partition is designated as the root filesystem (mounted at '/'). This is the correct file to check for the configured root partition, though note that the actual runtime mount may differ if the system was booted with different parameters or if the filesystem was remounted.

Answer

/var/log/dmesg

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/etc/passwd

Answer

/proc/partitions

Question 2

A user reports that they cannot save files to their home directory. You find that the disk is not full. What is the most likely cause related to hardware-based limitations?

Accepted Answer

The partition has run out of inodes.. Even when disk space is free, a filesystem can run out of inodes — the fixed-size data structures that track each file's metadata. Once all inodes are consumed, no new files can be created, producing 'No space left on device' errors despite available blocks. This is a hardware/filesystem-level limitation independent of raw capacity. The other options relate to memory, CPU, or firmware, which wouldn't specifically block file creation while space remains.

Answer

The RAM is corrupted.

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The CPU temperature is too high.

Answer

The BIOS settings are incorrect.

Question 3

You are troubleshooting a network issue where a Linux server cannot reach an external website. The ping command to the gateway succeeds, but pinging the website IP fails. Which configuration file should you check to ensure the server can resolve domain names?

Accepted Answer

/etc/resolv.conf. The /etc/resolv.conf file is the standard Linux configuration file that specifies the DNS servers (nameservers) the system uses to resolve domain names into IP addresses. Since the server can ping the gateway but cannot ping the website by IP, the issue is likely name resolution, not routing. Checking /etc/resolv.conf ensures that valid DNS server entries are present and reachable. Without correct nameserver entries, the system cannot translate domain names to IPs, causing ping to fail even if the network path is fine.

Answer

/etc/network/interfaces

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/etc/sysconfig/network

Answer

/etc/hosts

Question 4

You are configuring a static IP address on a Debian-based server. Which file must be modified to make this change persistent across reboots?

Accepted Answer

/etc/network/interfaces. On Debian-based systems, persistent network configuration is stored in /etc/network/interfaces (or /etc/network/interfaces.d/), where you define the interface with iface eth0 inet static, address, netmask, and gateway. Editing this file and restarting networking (or rebooting) makes the static IP persist. The other files serve different purposes and do not configure interface IP addressing.

Answer

/etc/hosts

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/etc/sysconfig/network-scripts/ifcfg-eth0

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/etc/resolve.conf

Question 5

A user is complaining that their application runs slowly. You suspect the system is swapping excessively. Which command shows the current usage of swap space?

Accepted Answer

swapon -s. The free command displays total, used, and free swap space.

Answer

fdisk -l

Answer

vmstat

Answer

mount

Question 6

Which command is used to safely shut down the system immediately?

Accepted Answer

poweroff. The shutdown -h now command sends a signal to the init system to power off the machine.

Answer

reboot

Answer

exit

Question 7

You want to view the kernel's boot messages to check for driver initialization errors. Which command is most appropriate?

Accepted Answer

journalctl -b. dmesg reads the kernel ring buffer, which holds boot-time messages.

Answer

cat /var/log/auth.log

Answer

lsmod

Answer

modprobe

Question 8

You have modified a configuration file for a network service. Which command is best practice to test the configuration syntax before restarting the service?

Accepted Answer

apache2ctl -t. apache2ctl -t (equivalently 'apachectl configtest' or 'httpd -t') parses the Apache configuration files and reports syntax errors without restarting or reloading the service. This is the documented best practice for validating httpd.conf and included vhost files before applying changes, letting you catch typos and directive errors safely. It is the only option that actually tests configuration syntax rather than changing service state.

Answer

systemctl reload

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systemctl status

Answer

service name test

Question 9

A user on a Linux workstation wants to know which shell is currently active for their login session. Which command should they run?

Accepted Answer

echo $SHELL. The $SHELL environment variable is set at login and contains the path to the user's default shell. Displaying it with echo provides a direct, reliable answer. Other commands either list all processes, inspect account databases, or show kernel details, none of which identify the shell currently in use for the session.

Answer

uname -a

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cat /etc/passwd

Answer

ps -ef | grep bash

Question 10

A Linux user wants to change the permissions of a file named report.txt so that the owner can read and write, the group can read, and others have no access. The current permissions are rw-r--r--. Which command will set the permissions to rw-r-----?

Accepted Answer

chmod 640 report.txt. The desired permissions rw-r----- correspond to the octal digits 6 (owner: read+write), 4 (group: read), and 0 (others: none). The command chmod 640 report.txt sets these exact permissions. The other numeric modes either grant others read access or remove group read access, and while the symbolic mode can achieve the same result, the numeric mode is the standard and unambiguous answer expected in this context.

Answer

chmod u=rw,g=r,o= report.txt

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chmod 644 report.txt

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chmod 604 report.txt

Question 11

An administrator wants to view the current system load and active processes. Which utility is the most appropriate for a real-time monitor?

Accepted Answer

top. The `top` command provides a real-time, continuously updating view of system load, CPU usage, memory usage, and active processes, refreshing by default every few seconds. It is the standard interactive utility for live monitoring of system load and processes on Linux. This matches the requirement for a real-time monitor.

Answer

df -T

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ps aux

Answer

cat /proc/cpuinfo

Question 12

You are managing a Linux server and need to confirm the IP address assigned to the eth0 interface. Which command is most appropriate on modern distributions?

Accepted Answer

ip addr. The `ip addr` command is part of the iproute2 suite, which has replaced the legacy net-tools package on modern Linux distributions. It queries the kernel's network stack directly via netlink sockets and displays all interfaces with their assigned IPv4/IPv6 addresses, MAC addresses, and link state. Running `ip addr` (or its shorthand `ip a`) shows the eth0 interface with its inet address, making it the correct modern tool for this task.

Answer

ifconfig

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route -n

Answer

netstat -rn

Question 13

A technician needs to identify the amount of RAM installed in a server without opening the chassis. Which command provides this information from the command line?

Accepted Answer

free -m. `free -m` reads memory statistics from /proc/meminfo and displays total, used, free, shared, buff/cache, and available RAM in mebibytes. It is the standard command-line tool for reporting installed and currently used physical memory without touching the hardware.

Answer

uptime

Answer

lsblk

Answer

df -h

Question 14

You have added a new hard drive to your Linux server, but the system does not automatically recognize the device. What is the first step you should take to verify if the kernel detects the hardware?

Accepted Answer

Examine the output of dmesg.. The `dmesg` command prints the kernel ring buffer, which contains messages from the kernel during boot and runtime, including hardware detection events. When a new hard drive is added, the kernel logs its detection (or failure to detect) there, making `dmesg` the first place to verify whether the kernel recognized the device. This is the standard first diagnostic step for hardware recognition issues.

Answer

Reinstall the operating system.

Answer

Run the top command.

Answer

Edit the /etc/fstab file.

Question 15

A small business owner wants to implement a server that allows for long-term support and stability for critical financial applications. Which distribution strategy should they prioritize?

Accepted Answer

Choosing a distribution that offers an LTS version with a long support lifecycle.. For long-term support and stability of critical financial applications, an LTS (Long Term Support) distribution is ideal because it provides a stable, well-tested platform with security updates for an extended period (often 5-10 years). This minimizes disruptive changes and ensures reliability. Rolling releases and desktop-focused distributions prioritize frequent updates or ease of use, not long-term stability.

Answer

Using a desktop-focused distribution for ease of installation.

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Compiling the kernel from source to match the specific hardware.

Answer

Selecting a rolling release distribution for frequent kernel updates.

Question 16

Which command is used to display the current directory path in the terminal?

Accepted Answer

pwd. The 'pwd' command (print working directory) outputs the absolute path of the directory the shell is currently in. It reads the shell's current directory state and prints it to standard output, which is exactly what the question asks for.

Answer

ls

Answer

dir

Answer

cd

Question 17

A developer needs to know the kernel version currently running on the server. Which command provides this information?

Accepted Answer

uname -r. `uname -r` prints the kernel release version (e.g., 5.15.0-91-generic) by invoking the uname() system call, which reads kernel information directly. The -r flag specifically returns the kernel release, while -a returns all fields. This is the canonical way to check the running kernel version on Linux.

Answer

ver

Answer

hostnamectl

Answer

cat /etc/issue

Question 18

You are setting up a local network and need to verify the path traffic takes to reach a remote host. Which command should you use?

Accepted Answer

traceroute. `traceroute` is designed to map the path packets take to a remote host by sending probes with incrementally increasing TTL values and collecting ICMP Time Exceeded responses from each hop. This directly answers the question of which routers traffic traverses to reach the destination.

Answer

nmap

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ping

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dig

Question 19

You need to ensure that a server's time is synchronized with an external time source to prevent authentication errors. Which daemon is responsible for this?

Accepted Answer

chronyd. chronyd is the NTP daemon on modern RHEL/CentOS/Fedora and many other distributions, responsible for synchronizing the system clock with external time sources. Accurate time is critical for Kerberos authentication, TLS certificate validation, and log correlation. The other daemons handle scheduling, remote access, and logging, not time synchronization.

Answer

cron

Answer

sshd

Answer

rsyslogd

Question 20

A system administrator is checking for hardware errors in the logs. Where are general system messages usually stored?

Accepted Answer

/var/log/syslog. General system messages on most Linux distributions are written to /var/log/syslog (Debian/Ubuntu) or /var/log/messages (RHEL/CentOS). The /var/log directory is the standard location for system and application logs, and syslog is the traditional catch-all for kernel, daemon, and service messages.

Answer

/etc/log/

Answer

/proc/logs

Answer

/tmp/logs