Most Asked Linux Interview Questions:-
1. What is Linux?
- Linux is an open-source operating system kernel that serves as the core of various Linux distributions.
2. What is a Linux distribution?
- A Linux distribution, or distro, is a complete operating system that includes the Linux kernel, software packages, and tools.
3. Explain the Linux file hierarchy.
- The Linux file system hierarchy starts with the root directory ("/") and includes directories like /bin, /etc, /home, /usr, /var, and others.
4. What is the root user in Linux?
- The root user is the superuser with administrative privileges, allowing full control over the system.
5. How do you change the password for a user in Linux?
- Use the `passwd` command, followed by the username to change a user's password.
6. What is a shell in Linux?
- A shell is a command-line interface that allows users to interact with the Linux operating system.
7. Name a few popular Linux shells.
- Bash (Bourne Again Shell), Zsh, and Fish are some popular Linux shells.
8. What is a PID in Linux?
- PID stands for Process ID. It is a unique number assigned to each running process.
9. How do you list all running processes in Linux?
- Use the `ps` command or `top` command to list running processes.
10. What is a daemon in Linux?
- A daemon is a background process that runs without user interaction, typically started at system boot.
11. How do you install software in Linux?
- You can install software using package managers like `apt`, `yum`, or `dnf`, depending on your Linux distribution.
12. What is the purpose of the `chmod` command?
- The `chmod` command is used to change the permissions of files and directories in Linux.
13. How do you search for a file in Linux?
- Use the `find` command to search for files and directories based on various criteria.
14. Explain the `grep` command.
- `grep` is used to search and filter text using patterns within files or standard input.
15. What is an inode in Linux?
- An inode is a data structure that stores metadata about a file, such as permissions, ownership, and location on disk.
16. How do you create a symbolic link in Linux?
- Use the `ln -s` command followed by the source and target file or directory.
17. What is the purpose of the `df` command?
- The `df` command displays disk space usage on Linux systems.
18. Explain the purpose of the `du` command.
- The `du` command is used to calculate the disk space used by files and directories.
19. How do you check the network configuration in Linux?
- Use the `ifconfig` or `ip` command to view network configurations.
20. What is SSH and how do you use it in Linux?
- SSH (Secure Shell) is a protocol used for secure remote access to Linux servers. Use `ssh user@hostname` to connect.
21. How do you schedule tasks in Linux?
- Use the `cron` and `at` utilities to schedule tasks at specific times or intervals.
22. Explain the `tar` command.
- `tar` is used to create and extract archives (tarballs) in Linux.
23. How do you check system hardware information in Linux?
- Use commands like `lscpu`, `lshw`, and `lspci` to check hardware information.
24. What is GRUB in Linux?
- GRUB (Grand Unified Bootloader) is a bootloader used to manage the boot process of a Linux system.
25. What is the purpose of the `systemd` init system?
- `systemd` is a system and service manager that initializes and manages system services during boot.
26. How do you start and stop services using `systemd`?
- Use commands like `systemctl start`, `systemctl stop`, and `systemctl enable` to manage services.
27. What is the purpose of the `crontab` command?
- `crontab` is used to manage cron jobs for individual users.
28. Explain the difference between hard links and symbolic links.
- Hard links point to the same inode on disk, while symbolic links are separate files that reference a target.
29. What is a kernel module in Linux?
- A kernel module is a piece of code that can be loaded and unloaded into the Linux kernel without rebooting.
30. How do you list all available network interfaces in Linux?
- Use the `ifconfig` or `ip link show` command to list network interfaces.
31. What is a runlevel in Linux?
- Runlevels are various operating modes of a Unix-based operating system, used to control the system's state.
32. How do you check the contents of a file without opening it in Linux?
- Use the `cat`, `less`, or `more` commands to view file contents.
33. Explain the `ssh-keygen` command.
- `ssh-keygen` is used to generate SSH key pairs for secure authentication.
34. How do you check available memory in Linux?
- Use the `free` command to display information about available memory.
35. What is the purpose of the `ps` command with options like `-aux`?
- The `ps` command with options like `-aux` displays a detailed list of all processes.
36. What is a swap partition in Linux?
- A swap partition is used as virtual memory when physical RAM is fully utilized.
37. How do you change the hostname of a Linux system?
- Edit the `/etc/hostname` file and use the `hostname` command.
38. What is the purpose of the `chmod +x` command on a script file?
- It grants execute permission to a script, allowing it to be run.
39. How do you recursively copy a directory in Linux?
- Use the `cp -r` or `rsync` command to copy directories and their contents.
40. What is SELinux, and how does it enhance security in Linux?
- SELinux (Security-Enhanced Linux) is a security framework that enforces mandatory access controls to enhance security.
41. How do you create a compressed archive using the `tar` command?
- Use the `-z` or `-j` option to create compressed tar archives with gzip or bzip2 compression, respectively.
42. What is a firewall in Linux, and how do you configure it?
- A firewall controls incoming and outgoing network traffic. You can configure it using tools like `iptables` or `firewalld`.
43. Explain the `chown` command.
- `chown` is used to change the ownership of files and directories in Linux.
44. How do you find the IP address of a Linux system?
- Use the `ifconfig`, `ip addr show`, or `hostname -I` command to find the IP address.
45. What is a package manager, and how does it work in Linux?
- A package manager is a tool for installing, updating, and managing software packages. Examples include `apt`, `yum`, and `dnf
`.
46. What is the purpose of the `/etc/fstab` file?
- `/etc/fstab` is a configuration file that lists disk drives and partitions to be mounted at boot.
47. How do you monitor system resource usage in Linux?
- Use tools like `top`, `htop`, and `atop` to monitor CPU, memory, and disk usage.
48. Explain the `awk` command in Linux.
- `awk` is a powerful text processing tool used to manipulate and analyze data.
49. What is the difference between a process and a thread?
- A process is an independent program with its own memory and resources, while a thread is a lightweight subprocess sharing resources within a process.
50. How do you update the Linux system and its packages?
- Use package manager commands like `apt update && apt upgrade` (for Debian/Ubuntu) or `yum update` (for CentOS/RHEL) to update the system and packages.
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