100+ Linux Administrator Interview Questions and Answers

Linux commands are essential for a Linux Administrator. Here are a few commonly used commands:

• ls - list directory contents

• cd - change directory

• mkdir - make directory

• rm - remove files or directories

• cp - copy files or directories

• mv - move or rename files or directories

• grep - search for a pattern in a file

• ps - display information about running processes

• top - display system resource usage

• chmod - change file permissions

• sudo - execute a command as a superuser

• apt-get - package manag...read more

Accessing one server from another can be done using SSH (Secure Shell) protocol.

• Use SSH (Secure Shell) protocol to securely access another server

• Use the 'ssh' command followed by the username and IP address of the target server

• Provide the password or use SSH keys for authentication

• Example: ssh username@ip_address

NFS stands for Network File System. It is a protocol used for sharing files/folders between Unix/Linux systems over a network.

• NFS allows a user on a client computer to access files over a network as if they were on the local hard drive.

• The NFS configuration file is /etc/exports, which lists the directories that can be exported to remote systems.

• NFS uses RPC (Remote Procedure Call) to communicate between the client and server.

• NFS can be used to share files between Linux/Unix s...read more

DHCP stands for Dynamic Host Configuration Protocol. It is a network protocol that automatically assigns IP addresses to devices on a network.

• DHCP server assigns IP addresses to devices on a network

• It also provides other network configuration information such as subnet mask and default gateway

• DHCP uses a lease mechanism to manage IP address assignments

• DHCP operates on the client-server model

• Example: When a device connects to a network, it sends a DHCP request to the DHCP serv...read more

A Linux administrator is responsible for managing and maintaining Linux-based systems.

• Installs, configures, and updates Linux operating systems and software

• Monitors system performance and troubleshoots issues

• Manages user accounts and permissions

• Implements security measures to protect systems and data

• Automates tasks using scripting languages like Bash or Python

pfSense is an open-source firewall and router distribution based on FreeBSD. Postfix is a mail transfer agent (MTA) used for sending and receiving emails.

• pfSense is a powerful, feature-rich firewall and router platform

• It provides advanced security features such as VPN, traffic shaping, and intrusion detection

• Postfix is a widely used MTA that routes and delivers email messages

• It is known for its flexibility, scalability, and robustness

• Postfix supports various authentication me...read more

LVM stands for Logical Volume Manager, a tool used to manage disk space in a flexible manner.

• LVM allows for dynamic resizing of logical volumes without the need to unmount the filesystem.

• It provides features like volume resizing, snapshots, and striping.

• Physical volumes are combined into volume groups, which are then divided into logical volumes.

• Example: Creating a new logical volume from free space in a volume group using lvcreate command.

LDAP can be used to manage user accounts by storing user information in a centralized directory.

• Set up LDAP server and configure it to store user account information

• Use LDAP client tools to manage user accounts such as creating, modifying, or deleting accounts

• Authenticate users against LDAP server for access control

• Implement LDAP schema to define attributes and object classes for user accounts

The /mnt directory is used as a mount point for temporary mounting of filesystems, and fstab is a configuration file that lists filesystems to be mounted at boot.

• The /mnt directory is commonly used for temporarily mounting external storage devices or network shares.

• The fstab file is located at /etc/fstab and contains information about filesystems to be mounted at boot time.

• Entries in fstab include the device to mount, the mount point, filesystem type, mount options, and dump ...read more

PID stands for Process ID, a unique identifier assigned to each running process in a system. Netstat is a command-line tool used to display network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.

• PID is a unique identifier assigned to each running process in a system

• Netstat is a command-line tool used to display network connections and related information

• PID helps in managing and monitoring processes in a system

• Netstat can ...read more

Programming language is a set of instructions used to create software applications.

• Programming languages are used to write code that computers can understand and execute.

• There are many programming languages such as Java, Python, C++, and JavaScript.

• Each programming language has its own syntax and rules for writing code.

• Programming languages can be classified into low-level and high-level languages.

• Examples of low-level languages include Assembly and Machine language, while hi...read more

rpm is a package manager for Red Hat-based systems, while yum is a high-level package manager that uses rpm as its backend.

• rpm is a low-level package manager that directly interacts with the system's package database and files

• yum is a high-level package manager that automates the process of dependency resolution and package installation

• yum can also automatically download and install dependencies for a package, while rpm does not have this capability

LVM (Logical Volume Manager) is a tool used to manage disk space by creating logical volumes from physical volumes.

• LVM allows for dynamic resizing of logical volumes without the need to unmount the filesystem

• To extend a logical volume, use the 'lvextend' command followed by the size to extend by and the logical volume name

• For example, to extend a logical volume named 'lv_data' by 100MB, the command would be 'lvextend -L +100M /dev/vg_data/lv_data'

SWAP partition is a dedicated space on a hard drive used as virtual memory when physical RAM is full.

• SWAP partition is used to supplement physical RAM by temporarily storing data that is not actively used.

• It helps prevent system crashes or slowdowns due to running out of memory.

• SWAP partition can be a dedicated partition on a hard drive or a swap file within the filesystem.

• Linux systems typically create a SWAP partition during installation.

• SWAP partition can be managed using ...read more

To troubleshoot network issues, start by checking physical connections, verifying network settings, testing connectivity, and analyzing network traffic.

• Check physical connections (cables, ports, etc.)

• Verify network settings (IP address, subnet mask, gateway, DNS)

• Test connectivity using tools like ping, traceroute, and netcat

• Analyze network traffic with tools like Wireshark or tcpdump

RAID stands for Redundant Array of Independent Disks. RPM stands for Red Hat Package Manager.

• RAID is a data storage technology that combines multiple physical disk drives into a single logical unit for data redundancy, performance improvement, or both.

• There are different RAID levels such as RAID 0, RAID 1, RAID 5, RAID 6, etc.

• RPM is a package management system used in Linux distributions like Red Hat, CentOS, Fedora, etc.

• It is used to install, update, and remove software pack...read more

Disk partitions can be resolved by resizing, moving, or merging partitions using tools like GParted or fdisk.

• Use GParted or fdisk to resize partitions to allocate more space to a partition.

• Move partitions to rearrange the layout of the disk.

• Merge partitions to combine multiple partitions into one.

• Backup data before making any changes to disk partitions.

ls command lists files and directories in a directory, while ll command provides detailed information about files and directories.

• ls command displays a simple list of files and directories in a directory

• ll command provides detailed information such as permissions, owner, group, size, and modification date of files and directories

• ls -l command is equivalent to ll command

• ls -a command lists all files including hidden files

The command finds files larger than 50k in the root directory and lists them in reverse chronological order.

• Use 'find' command to search for files in a directory

• Specify the type of file with -type f

• Filter files by size using -size 50k

• Execute 'ls -lrth' on the found files using -exec {} ls -lrth \;

System load can be checked using the 'uptime' command or by using tools like 'top' or 'htop'.

• Use the 'uptime' command to see the system load averages for the past 1, 5, and 15 minutes.

• Use the 'top' command to view real-time system information including load averages.

• Use the 'htop' command for a more user-friendly and interactive way to view system load and resource usage.

To configure Apache server, modify the httpd.conf file and add virtual hosts.

• Edit the httpd.conf file located in /etc/httpd/conf/ directory

• Add virtual hosts to the httpd.conf file to host multiple websites

• Restart the Apache server using the command 'systemctl restart httpd'

• Configure SSL/TLS certificates for secure connections

Troubleshooting systems involves identifying and resolving issues to ensure optimal performance.

• Start by gathering information about the issue, such as error messages or recent changes.

• Use system monitoring tools to check for any abnormalities in performance or resource usage.

• Isolate the problem by testing different components or configurations.

• Check system logs for any clues or errors that may indicate the root cause.

• Consult documentation, online resources, or colleagues for...read more

Cloud computing is the delivery of computing services over the internet, including servers, storage, databases, networking, software, and more.

• Cloud computing allows users to access and use resources on-demand without the need for physical infrastructure.

• It offers scalability, flexibility, cost-effectiveness, and increased efficiency.

• Examples of cloud computing services include Amazon Web Services (AWS), Microsoft Azure, and Google Cloud Platform.

LVM stands for Logical Volume Manager, a tool used to manage disk storage in Linux systems.

• LVM allows for dynamic resizing of logical volumes without downtime.

• It consists of physical volumes, volume groups, and logical volumes.

• Commands like pvcreate, vgcreate, lvcreate are used to create and manage LVM.

• LVM provides flexibility in managing storage space by allowing logical volumes to span multiple physical disks.

L'un addition and removal complete process involves adding or removing software packages in a Linux system.

• To add software packages, use the 'apt-get install' command followed by the package name.

• To remove software packages, use the 'apt-get remove' command followed by the package name.

• You can also use 'apt-get purge' to remove a package along with its configuration files.

• Always update the package list before adding or removing packages using 'apt-get update'.

Types of memory dumps in Windows include Complete Memory Dump, Kernel Memory Dump, Small Memory Dump, and Automatic Memory Dump.

• Complete Memory Dump - contains all the contents of physical memory at the time of the crash

• Kernel Memory Dump - includes only kernel memory, useful for troubleshooting kernel mode crashes

• Small Memory Dump - contains minimal information about the crash, takes up less space

• Automatic Memory Dump - Windows decides which type of memory dump to create bas...read more

The boot process of Linux involves several stages, including BIOS, bootloader, kernel initialization, and system initialization.

• The boot process starts with the BIOS (Basic Input/Output System) initializing hardware and performing a Power-On Self-Test (POST).

• The bootloader, such as GRUB or LILO, is then loaded to locate and load the Linux kernel.

• The kernel initializes essential components, sets up memory, and mounts the root file system.

• The init process is started, which exec...read more

IP can be assigned using various methods like DHCP, static IP, or command-line tools like ifconfig or ip.

• DHCP assigns IP automatically to devices on the network

• Static IP is manually assigned to a device and remains the same

• ifconfig and ip are command-line tools used to assign IP

• Example: sudo ifconfig eth0 192.168.1.100 netmask 255.255.255.0

• Example: sudo ip addr add 192.168.1.100/24 dev eth0

To check logs in Linux server, use commands like 'tail', 'grep', 'cat', 'less', 'journalctl', or navigate to log directories.

• Use 'tail' command to view the last few lines of a log file

• Use 'grep' command to search for specific keywords in log files

• Use 'cat' command to display the entire contents of a log file

• Use 'less' command to view log files interactively

• Use 'journalctl' command to access system logs managed by systemd

• Navigate to log directories like '/var/log/' to manually...read more

NFS server is a network file system server that allows clients to access files over the network as if they were on the local machine.

• NFS stands for Network File System

• It is a distributed file system protocol

• It allows a user on a client computer to access files over a network as if those files were on the local computer

• The NFS server exports one or more directories to the clients

• The clients can mount these directories and access the files in them

• Example: A Linux server can exp...read more

To resolve spamming and server load issues, take steps such as implementing spam filters, optimizing server configurations, and monitoring server performance.

• Implement spam filters to block unwanted emails and reduce server load

• Optimize server configurations by adjusting settings such as memory allocation and CPU usage

• Monitor server performance regularly to identify any spikes in load and address them promptly

Script to echo a line repeatedly

• Use a loop to echo the line multiple times

• Specify the number of times to repeat the line

• Example: for i in {1..5}; do echo 'Hello, World!'; done

tcpdump is used for network troubleshooting and analysis by capturing and analyzing network packets.

• Captures network packets for analysis

• Helps in troubleshooting network issues

• Can be used to monitor network traffic

• Provides detailed information about network communication

• Useful for security analysis and monitoring

Code to print table of any number in Python

• Use a loop to iterate from 1 to 10 (for a 10x table)

• Multiply the number by the current iteration value

• Print the result for each iteration

To create LVM, first create physical volumes, then create a volume group, and finally create logical volumes.

• Use pvcreate command to create physical volumes

• Use vgcreate command to create volume group

• Use lvcreate command to create logical volumes

• Use lvextend command to extend logical volumes

• Use lvreduce command to reduce logical volumes

The port number for DHCP is 67 (server) and 68 (client).

• DHCP server uses port 67 for incoming requests from clients

• DHCP client uses port 68 for outgoing requests to servers

Domain Name System (DNS) is a system that translates domain names to IP addresses, allowing users to access websites using human-readable names.

• DNS is like a phone book for the internet, translating domain names (like google.com) to IP addresses (like 172.217.3.206).

• DNS servers store records of domain names and their corresponding IP addresses.

• DNS helps users access websites by resolving domain names to IP addresses in the background.

• DNS also supports other types of records l...read more

FTP port number is 21.

• FTP port number is used for transferring files over a network.

• It is a default port number for FTP protocol.

• FTP clients connect to port 21 on the server to initiate a file transfer.

• FTP servers listen on port 21 for incoming connections.

Yes, I have set an IP address for various devices and servers in a network.

• Yes, I have experience setting static IP addresses for servers in a data center.

• I have configured dynamic IP addresses for devices on a local network using DHCP.

• I have troubleshooted network connectivity issues related to IP address conflicts.

To check WWN number, use commands like 'lsscsi' or 'lsblk' in Linux.

• Use 'lsscsi' command to list SCSI devices and their WWN numbers

• Use 'lsblk' command to list block devices and their WWN numbers

JIT Compiler stands for Just-In-Time Compiler. It is a type of compiler that compiles code during runtime.

• JIT Compiler is used to improve the performance of applications by compiling code on the fly.

• It is commonly used in Java and .NET environments.

• JIT Compiler compiles code into machine code, which can be executed directly by the CPU.

• It can also optimize code by removing unnecessary instructions and reducing memory usage.

• Examples of JIT Compiler include HotSpot for Java and ...read more

LVM can be configured using the lvcreate, vgcreate and pvcreate commands.

• Create physical volumes using pvcreate command

• Create volume groups using vgcreate command

• Create logical volumes using lvcreate command

• Extend or reduce logical volumes using lvextend or lvreduce command

• Mount the logical volumes to use them

• Use the lvdisplay, vgdisplay and pvdisplay commands to view the LVM configuration

To setup local repository, create a directory, copy packages, create repo file, and run createrepo command.

• Create a directory to store packages

• Copy packages to the directory

• Create a repo file in /etc/yum.repos.d/ directory

• Add necessary information in the repo file

• Run createrepo command to create repository metadata

Updating the system involves installing the latest security patches and software updates.

• Use the package manager to update the system

• For Debian-based systems, use apt-get update and apt-get upgrade

• For Red Hat-based systems, use yum update

• Regularly check for updates and install them promptly

• Reboot the system after updating to ensure changes take effect

NFS (Network File System) is a distributed file system protocol allowing a user on a client computer to access files over a network as if they were local.

• NFS allows multiple clients to access shared files on a network.

• It operates on the client-server model.

• Apache is a popular open-source web server software used to serve web content over the internet.

• Apache can host websites, applications, and web services.

• Both NFS and Apache are commonly used in Linux environments.

Booting is the process of starting a computer and loading the operating system into memory.

• When the computer is turned on, the BIOS (Basic Input/Output System) performs a Power-On Self Test (POST)

• The BIOS then searches for a bootable device, such as a hard drive or CD-ROM

• Once a bootable device is found, the BIOS loads the boot loader, which is responsible for loading the operating system

• The boot loader then loads the kernel, which initializes the operating system and starts t...read more

SIEM integration refers to the process of connecting a Security Information and Event Management system with other security tools and systems.

• SIEM integration allows for centralized monitoring and analysis of security events across an organization.

• It enables correlation of data from various sources to detect and respond to security incidents more effectively.

• Examples of SIEM integration include connecting SIEM with firewalls, intrusion detection systems, and endpoint security...read more