Linux Server Support Engineer Job Interview Questions and Answers for Freshers Part 1

Linux Server Support Engineer Job Interview Questions and Answers:

Q: What is Linux? A: Linux is an open-source, Unix-like operating system kernel created by Linus Torvalds. It is widely used for its stability, security, and flexibility in various environments including servers, desktops, and embedded systems.
Q: What are the main differences between Linux and Windows operating systems? A: Linux is open-source and free, while Windows is a proprietary operating system. Linux provides more flexibility and control to users, is considered more secure, and has a more complex command-line interface. Windows is more user-friendly with a graphical user interface (GUI) and has broader commercial support.
Q: What is a Linux kernel? A: The Linux kernel is the core component of the Linux operating system. It manages system resources, hardware communication, and system calls from applications.
Q: How do you check the current version of the Linux kernel? A: You can check the current version of the Linux kernel by running the command uname -r.
Q: What is the purpose of the ls command? A: The ls command lists the contents of a directory.
Q: How do you change file permissions in Linux? A: File permissions can be changed using the chmod command. For example, chmod 755 filename changes the permissions of filename.
Q: What does chmod 755 filename do? A: This command sets the permissions of filename so that the owner can read, write, and execute the file, while others can only read and execute it.
Q: What is the difference between su and sudo? A: su (substitute user) allows you to switch to another user account, while sudo (superuser do) allows a permitted user to execute a command as the superuser or another user.
Q: How do you display the contents of a file in Linux? A: You can display the contents of a file using commands like cat, less, more, head, or tail.
Q: What is the purpose of the /etc/passwd file? A: The /etc/passwd file stores user account information, including usernames, UID, GID, home directory, and shell.
Q: How do you check the disk space usage in Linux? A: You can check disk space usage using the df command for file systems and du command for directory sizes.
Q: What is a package manager in Linux? A: A package manager is a tool that automates the process of installing, upgrading, configuring, and removing software packages. Examples include apt for Debian-based systems and yum or dnf for Red Hat-based systems.
Q: How do you update all installed packages on a Debian-based system? A: Use sudo apt update to update the package index and sudo apt upgrade to upgrade all installed packages.
Q: What is the difference between a hard link and a soft link in Linux? A: A hard link is a direct reference to the file’s inode, while a soft link (or symbolic link) is a pointer to the file name. Hard links cannot reference directories and cannot span across different file systems.
Q: What is cron in Linux? A: cron is a time-based job scheduler in Unix-like operating systems used to schedule repetitive tasks.
Q: How do you schedule a task to run at 3 AM every day using cron? A: Edit the crontab file using crontab -e and add the line 0 3 * * * /path/to/command.
Q: What is the grep command used for? A: The grep command searches for a specified pattern in files and outputs the matching lines.
Q: How do you search for a specific string in a file using grep? A: Use grep 'search_string' filename.
Q: What is the top command used for? A: The top command displays real-time system information, including CPU and memory usage, running processes, and system uptime.
Q: How do you kill a process in Linux? A: Use the kill command followed by the process ID (PID), e.g., kill 1234.
Q: What is the purpose of the /var/log directory? A: The /var/log directory stores system and application log files.
Q: How do you view the last 10 lines of a log file? A: Use the tail -n 10 logfile command.
Q: What is SSH and what is it used for? A: SSH (Secure Shell) is a protocol used to securely connect to a remote machine and execute commands.
Q: How do you connect to a remote server using SSH? A: Use the command ssh username@hostname.
Q: What is a firewall in the context of Linux? A: A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. Tools like iptables and firewalld are used to configure firewalls in Linux.
Q: How do you check active network connections in Linux? A: Use the netstat or ss command to check active network connections.
Q: What is the ifconfig command used for? A: The ifconfig command is used to configure network interfaces. However, it is deprecated in favor of the ip command.
Q: How do you check the IP address of your machine using the ip command? A: Use the command ip addr show.
Q: What is a runlevel in Linux? A: A runlevel is a state of init and the whole system that defines what system services are operating. For example, runlevel 3 is multi-user mode without a graphical interface, and runlevel 5 is multi-user mode with a graphical interface.
Q: How do you change the runlevel in Linux? A: You can change the runlevel using the init or telinit command followed by the desired runlevel number.
Q: What is the sudo command used for? A: The sudo command allows permitted users to execute a command as the superuser or another user, as specified by the security policy.
Q: How do you add a new user in Linux? A: Use the useradd command followed by the username, e.g., sudo useradd newuser.
Q: How do you change a user’s password in Linux? A: Use the passwd command followed by the username, e.g., sudo passwd newuser.
Q: What is a daemon in Linux? A: A daemon is a background process that runs continuously and usually provides or manages a service.
Q: How do you start a daemon in Linux? A: You can start a daemon using system service management commands like systemctl start servicename or service servicename start.
Q: What is the systemctl command used for? A: The systemctl command is used to examine and control the systemd system and service manager.
Q: How do you check the status of a service using systemctl? A: Use the command systemctl status servicename.
Q: How do you enable a service to start on boot using systemctl? A: Use the command systemctl enable servicename.
Q: What is the /etc/fstab file used for? A: The /etc/fstab file contains information about disk drives and partitions and is used by the system to automatically mount partitions on boot.
Q: What is swap space in Linux? A: Swap space is a designated area on a hard drive that the system can use as additional RAM.
Q: How do you check memory usage in Linux? A: Use the free command to check memory usage.
Q: How do you list all currently loaded kernel modules? A: Use the lsmod command to list all currently loaded kernel modules.
Q: How do you load a kernel module? A: Use the modprobe command followed by the module name, e.g., sudo modprobe modulename.
Q: What is a shell in Linux? A: A shell is a command-line interpreter that provides a user interface for the Unix-like operating systems. Examples include bash, sh, and zsh.
Q: How do you find the PID of a process? A: Use the ps command along with grep to find the PID, e.g., ps aux | grep processname.
Q: What is a tarball in Linux? A: A tarball is a compressed archive file created using the tar command, often with extensions like .tar, .tar.gz, or .tar.bz2.
Q: How do you extract a tarball? A: Use the tar command followed by -xvf, e.g., tar -xvf filename.tar.gz.
Q: What is the purpose of the alias command? A: The alias command is used to create shortcuts for commands. For example, alias ll='ls -la' creates an alias ll for the command ls -la.
Q: How do you display all environment variables? A: Use the printenv or env command to display all environment variables.
Q: How do you find out how long the system has been running? A: Use the uptime command to find out how long the system has been running.