Linux Interview Handbook

Top 150 Linux interview questions and answers.

1. Linux Fundamentals

1. What is Linux? - An open-source Unix-like operating system.
2. Who created Linux? - Linus Torvalds.
3. What is a kernel? - The core component of Linux.
4. What is GNU/Linux? - The Linux kernel plus GNU tools.
5. Why is Linux popular? - It is open source, stable, and secure.
6. What is a distribution (distro)? - A packaged version of Linux.
7. Examples of Linux distros? - Ubuntu, Arch Linux, Debian, Fedora.
8. What is a shell? - A command-line interpreter.
9. Popular shells? - Bash, Zsh, Fish.
10. What is a terminal? - An interface to interact with the shell.

2. File System

11. What is the Linux file system? - A hierarchical directory structure.
12. Root directory? - /
13. Home directory? - /home
14. Root user home? - /root
15. Configuration files? - /etc
16. User programs? - /usr
17. Temporary files? - /tmp
18. Variable data? - /var
19. Device files? - /dev
20. Boot files? - /boot

3. Basic Commands

21. pwd? - Print current directory.
22. ls? - List files.
23. cd? - Change directory.
24. mkdir? - Create directory.
25. rmdir? - Remove empty directory.
26. rm? - Delete files.
27. cp? - Copy files.
28. mv? - Move or rename files.
29. touch? - Create an empty file.
30. clear? - Clear the terminal.

4. File Operations

31. cat? - Display file content.
32. less? - View file page by page.
33. more? - Basic file viewer.
34. head? - Show first lines of a file.
35. tail? - Show last lines of a file.
36. tail -f? - Live log monitoring.
37. nano? - Terminal text editor.
38. vim? - Advanced text editor.
39. wc? - Count words and lines.
40. file? - Identify file type.

5. User Management

41. Who is the current user? - whoami
42. Add user? - useradd
43. Delete user? - userdel
44. Change password? - passwd
45. Switch user? - su
46. Execute as root? - sudo
47. List users? - cat /etc/passwd
48. User ID? - UID
49. Group ID? - GID
50. Root user UID? - 0

6. Permissions

51. What are Linux permissions? - Read, write, and execute.
52. Read permission? - r
53. Write permission? - w
54. Execute permission? - x
55. Check permissions? - ls -l
56. Change permissions? - chmod
57. Change ownership? - chown
58. Change group? - chgrp
59. Permission 777? - Full access.
60. Permission 755? - Owner full, others read and execute.

7. Process Management

61. What is a process? - A running program.
62. Show running processes? - ps
63. Detailed processes? - top
64. Modern alternative? - htop
65. Process ID? - PID
66. Kill process? - kill PID
67. Force kill? - kill -9 PID
68. Background process? - command &
69. Foreground process? - Active terminal process.
70. Show jobs? - jobs

8. Networking

71. Check IP address? - ip addr
72. Old command? - ifconfig
73. Test connectivity? - ping
74. DNS lookup? - nslookup
75. Route information? - ip route
76. Download files? - wget
77. Alternative download tool? - curl
78. Open ports? - ss -tuln
79. SSH? - Secure Shell.
80. SSH port? - 22

9. Package Management

81. Ubuntu package manager? - apt
82. Update packages? - apt update
83. Upgrade packages? - apt upgrade
84. Install package? - apt install
85. Remove package? - apt remove
86. Arch package manager? - pacman
87. Update Arch Linux? - pacman -Syu
88. Fedora package manager? - dnf
89. Search package? - apt search
90. Package information? - apt show

10. Storage Management

91. Show disk usage? - df -h
92. Show folder size? - du -sh
93. List partitions? - lsblk
94. Mount file system? - mount
95. Unmount file system? - umount
96. What is swap? - Disk-based virtual memory.
97. Show memory usage? - free -h
98. Disk partition tool? - fdisk
99. Modern partition tool? - parted
100. What is LVM? - Logical Volume Manager.

11. Advanced Commands

101. grep? - Search text.
102. find? - Search files.
103. locate? - Fast file search.
104. awk? - Text processing.
105. sed? - Stream editor.
106. xargs? - Build command arguments.
107. sort? - Sort text.
108. uniq? - Remove duplicates.
109. cut? - Extract columns.
110. tr? - Translate characters.

12. Shell Scripting

111. What is a shell script? - A file containing shell commands.
112. Script extension? - .sh
113. Execute script? - bash script.sh
114. Make executable? - chmod +x
115. Print text? - echo
116. Read input? - read
117. Conditional statement? - if
118. Loop types? - for, while
119. Function in Bash? - A reusable code block.
120. Variables? - Store values.

13. systemd and Services

121. What is systemd? - Linux service manager.
122. Start service? - systemctl start
123. Stop service? - systemctl stop
124. Restart service? - systemctl restart
125. Service status? - systemctl status
126. Enable service? - systemctl enable
127. Disable service? - systemctl disable
128. View logs? - journalctl
129. Boot logs? - journalctl -b
130. List services? - systemctl list-units

14. Most Asked Interview Questions

131. Linux vs Windows?
132. What is kernel?
133. What is shell?
134. What is root user?
135. chmod vs chown?
136. Process vs thread?
137. What is SSH?
138. What is a cron job?
139. What is systemd?
140. What is swap memory?

15. Top 10 Commands Every Developer Must Know

141. ls
142. cd
143. pwd
144. grep
145. find
146. cat
147. chmod
148. chown
149. ps
150. kill

Linux Master Checklist

• Linux basics
• Kernel
• Shell
• File system
• Commands
• Users
• Groups
• Permissions
• Processes
• Networking
• SSH
• Package management
• Disk management
• grep
• find
• awk
• sed
• Bash scripting
• systemd
• Logs

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End of Linux handbook.