20+ Linux Administrator Interview Questions and Answers for Freshers

Files can be transferred from one server to another using tools like SCP, SFTP, or rsync.

• Use SCP (Secure Copy Protocol) to securely transfer files between servers. Example: scp file.txt user@server2:/path/to/directory

• Use SFTP (SSH File Transfer Protocol) for interactive file transfers. Example: sftp user@server2

• Use rsync for efficient synchronization of files between servers. Example: rsync -avz file.txt user@server2:/path/to/directory

Check for any processes or open files using the file system, then force unmount if necessary.

• Check for any processes or applications currently using the file system with 'lsof' command

• Kill any processes that are using the file system if necessary

• Try unmounting the file system again using 'umount -l' to force unmount if needed

To get MAC based routing table, use 'ip neigh show' command. When pinging a server, kernel sends ICMP packets and updates ARP cache.

• Use 'ip neigh show' command to display MAC based routing table

• Kernel sends ICMP packets when pinging a server

• Kernel updates ARP cache with MAC address of the server

One performance tuning parameter is swappiness, which controls how often the system swaps data to disk.

• To set swappiness temporarily, use the 'sysctl' command: sysctl vm.swappiness=10

• To set swappiness permanently, edit the '/etc/sysctl.conf' file and add 'vm.swappiness=10'

• Another performance tuning parameter is 'dirty_ratio' which controls the percentage of system memory that can be filled with dirty pages before processes are forced to write them out to disk

• To set dirty_rati...read more

You can schedule a job regularly using cron jobs in Linux.

• Use the crontab command to edit the cron table

• Specify the schedule using the appropriate syntax (minute, hour, day of month, month, day of week)

• For example, to schedule a job to run every day at 3am, you would add the following line to the cron table: 0 3 * * * /path/to/command

NFS (Network File System) is a distributed file system protocol that allows a user on a client computer to access files over a network.

• NFS enables sharing of files and directories between multiple computers in a network.

• It provides transparent access to remote files as if they were local.

• NFS uses a client-server architecture where the server exports directories that can be mounted on client machines.

• It supports both read and write operations on shared files.

• NFS is commonly us...read more

sed command is used for text manipulation in Linux. Special permissions include setuid, setgid, and sticky bit.

• sed command is used for text substitution and manipulation in Linux

• Syntax: sed 's/pattern/replacement/g' filename

• Special permissions in Linux include setuid, setgid, and sticky bit

• Setuid: allows a user to execute a file with the permissions of the file owner

• Setgid: allows a user to execute a file with the permissions of the group owner

• Sticky bit: restricts the deleti...read more

Steps for file system creation involve partitioning, formatting, and mounting the file system.

• Partition the disk using tools like fdisk or parted

• Format the partition with a file system like ext4 or xfs

• Create a mount point directory

• Mount the file system to the mount point

• Update /etc/fstab to automatically mount the file system on boot

NFS stands for Network File System, a distributed file system protocol that allows a user on a client computer to access files over a network.

• NFS allows a user to access files on a remote server as if they were local files.

• It is commonly used in Unix and Linux environments for sharing files and directories.

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

• It provides centralized storage that can be accessed by multiple clients over a network.

• NF...read more

I harden my Linux server by implementing security measures to protect against potential threats.

• Regularly update the operating system and software to patch vulnerabilities

• Disable unnecessary services and ports to reduce attack surface

• Implement strong password policies and use SSH keys for authentication

• Set up a firewall to control incoming and outgoing traffic

• Monitor logs for suspicious activities and set up intrusion detection systems

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

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.

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 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

To remove older kernels in Linux, use package management tools like apt or yum.

• Use 'apt autoremove' command in Debian-based systems to remove old kernels

• Use 'yum remove ' command in Red Hat-based systems to remove old kernels

• Check available kernels with 'uname -r' command before removing

To rollback a package, use package manager to uninstall current version and install previous version.

• Use package manager to uninstall current version of the package

• Install the previous version of the package using package manager

• Check for any dependencies that may need to be rolled back as well

To mount NFS, use the 'mount' command with the NFS server IP address and the mount point on the local machine.

• Use the 'mount' command followed by the NFS server IP address and the mount point on the local machine

• For example: sudo mount 192.168.1.100:/shared_folder /mnt/nfs_share

• Ensure that the NFS server is properly configured and accessible from the local machine

Workload in Linux refers to the amount of work being done by the system at a given time.

• Workload can include tasks such as running processes, handling network requests, and managing system resources.

• Monitoring workload is important for ensuring system performance and stability.

• Tools like top, htop, and sar can be used to track and analyze workload.

• High workload can lead to system slowdowns or crashes.

• Balancing workload across multiple servers can help improve overall system e...read more

Boot process is the sequence of steps that occur when a computer system is starting up.

• BIOS/UEFI initialization

• Loading the bootloader

• Loading the kernel

• Init process starts

• Launching user space processes

Patching involves applying updates to software to fix vulnerabilities and improve performance.

• Identify the software that needs to be patched

• Download the appropriate patches from the vendor's website

• Test the patches in a non-production environment before applying them to production systems

• Schedule downtime for applying patches to minimize disruption

• Document the patching process for future reference

The Linux kernel is the core component of the Linux operating system, responsible for managing hardware resources and providing essential services.

• The Linux kernel is open-source and developed by a community of developers worldwide.

• It is released under the GNU General Public License (GPL).

• The kernel version can be checked using the 'uname -r' command.

• Examples of popular Linux kernel versions include 2.6, 3.x, 4.x, and 5.x.