Top Linux Administrator Interview Questions for MNCs

Telephonic / F2F Interview Linux Administrator Questions

1. Tell me about yourself and current project you are supporting ?
2. How many servers you are handling/managing ?
3. What type of applications are hosted on those servers ?
4. What exactly you are managing on those servers ?
5. Explain about Server Hardening steps ?
6. How will you install any rpm packages ?
7. Difference between Hardlink & Softlink ?
8. What is the “lsof” command ?
9. What is the Swap Space ? Your swap space utilisation is full and How would you investigate and troubleshoot ?
10. How would you schedule the jobs ?
11. What is the syntax for crontab ?
12. Different run levels in Linux ?
13. What are the tools you are working ?
14. How do you check the disk utilization ?
15. What is “chown” command ?
16. What are the different owners for any file ? How did you find the permissions of any file ?
17. What is autofs and NFS ?
18. How you recover /etc/passwd file ?
19. What is NIC bonding ? why we use ?
20. How can you extend SWAP with LVM and without LVM ?
21. Booting issues you faced ?
22. Assign cronjob for every 1 hour ?
23. Explain about patching ?
24. User is unable to login ? Password policy is fine, how you troubleshoot ?
25. root user is unable to create the file, what could be the cause ?
26. How you update Kernel ?
27. What is RAID ? Explain about types of RAID levels ?
28. Difference between Soft link and Hard Link ?
29. How you extend root partition ?
30. Difference between yum and rpm ?
31. Explain about GRUB ?
32. How to find www port number ?
33. Explain about booting process ?
34. Explain about OSI layers ?
35. Difference between TCP and UDP ?
36. What is DNS ? Explain about DNS configuration ?
37. What is DHCP procedure ?
38. What are the types of virtualization ?
39. How to add a server in Nagios ?
40. What is High Availability and Fault tolerance ?
41. What is NFS ?
42. Apache Configuration file
43. How you extend LVM ? Explain it
44. What are DNS Fields ? Use of DNS ?
45. How to find the redhat OS current version ?
46. Explain about Kickstart ?
47. Difference between FTP and SFTP ?
48. What are the fields in /et/shadow file ?
49. Brief introduction about yourself and current project supporting by you ?
50. How many servers do you manage in current project ? What type of servers you manage ?
51. How you login to the server ? which command you use for login ?
52. Which type of tickets P1/P2/P3/P4 you manage ?
53. How will you do OS Patching ?
54. How do you take backup ? What method ? When will you do ?
55. Different types of tools using in your project ?
56. What types of issues you faced in your experience ? How you troubleshoot ?
57. What is log rotation ?
58. What is single, rescue and emergency mode ?
59. How do you take snapshot of any server ?
60. What is ITIL process ?
61. How you build a server ?
62. What is initrd and initramfs ?
63. Ticketing tool using in your current project ?
64. What is Cluster ?
65. What is the difference between kill and kill -9 ?
66. How to see the last 10 lines of a file? How to see the continuously updating log file ?
67. How to find all files containing a specific string (e.g., “ENGINEER”) in a directory ?
68. What are the three Standard File descriptors in Linux ?
69. What is the purpose of “chroot” command in Linux ?
70. How can you monitor the performance of a Linux System ?
71. What is SELinux and how does it enhance security in Linux ?
72. How do you troubleshoot a network issue in Linux ?
73. What are systemd units and how do you manage them ?
74. What is the purpose of cron and daemon ?
75. How can you “find” files with specific permissions in Linux ?
76. Differences between IPV4 and IPV6 ?
77. How can you check the current disk usage of a filesystem in Linux ?
78. Explain the importance/significance of “fstab” file in Linux ?
79. What are Linux run levels, and how do they differ ?
80. Describe the purpose and use of “iptables” command in Linux ?
81. How can you check for memory leaks in a Linux Application ?
82. What are the steps to take when performing a kernel update on a production server ?
83. Explain how to setup a basic LAMP stack on a Linux Server ?
84. How does the Linux kernel handle memory management ?
85. Explain the concept of I/O scheduling in Linux ?
86. What is Kernel panic ? How would you respond to it ?
87. How you would troubleshoot high memory usage on a Linux server ?
88. How do you manage and automate software updates in Linux Environment ?
89. How do you configure a firewall on a Linux system using “iptables” ?
90. What are “cgroups” in Linux and how they are used ?
91. How can you recover a lost root password on a Linux server ?
92. How do you configure a static IP address on a Linux system ?
93. How can you schedule a specific task to run at a specific time in Linux ?
94. How can you secure SSH access to a Linux Server ?
95. What is the difference between “apt-get” and “apt-cache” ?
96. What is Docker Containerization and how does it differ from traditional virtualization ?
97. How do you implement disk quotas in Linux ?
98. Explain Linux process priorities and how to modify them ?
99. How do you configure OpenLDAP for centralized authentication ?
100. How do you implement Linux Traffic control for bandwidth management ?
101. Explain Linux capabilities and their role in security ?
102. How do you configure and manage Linux Audit system (auditd) ?
103. Explain network bonding in Linux and its different modes ?
104. What is multipath I/O and how do you configure it in Linux ?
105. What is kdump and how do you configure it ?
106. Explain Linux Kernel tuning using sysctl parameters ?
107. What is Linux DMZ implementation and how do you secure it ?
108. How do you implement Linux Kernel module signing for secure boot ?
109. How do you implement CPU pining in virtualization environments ?
110. Explain Linux Time synchronization using chrony and PTP ?
111. How do you implement Linux Power Management with TLP ?
112. What is disaggregated memory management in Linux ?
113. The server is running out of disk space. How do you identify the culprit files and clean up the disk ?
114. What is Package management: yum, dnf, apt – differences and usage ?
115. How do We Monitor System Performance and resource usage ?
116. How do you write a shell script to find and list files greater than 100 MB in size?
117. How can you manage users, groups, and permissions in Linux ?
118. How do you schedule tasks using cron ?
119.  What is SSL and why it’s important for secure communication ?
120. Tell me Port numbers in Linux (HTTP, HTTPS, SSH, FTP, DNS) ?
121. Explain the Linux filesystem hierarchy and its key directories ?
122. If a partition is corrupted. How do we recover it ?
123. How do you check which process is using a particular file system ?
124. Difference between /dev/sda and /dev/sdb2 ?
125. A user cannot write to a directory despite having write permission, what could be the issue ?
126. You added a new disk, how do you partition and format it for use?
127. If you accidentally deleted a large file that was open by a process. How do you free the space ?
128. How do you mount a new disk automatically at boot time ?
129. A file system is full but ” du ” shows less usage. What could be the reason ?
130. How do you find a file named “app_var.log” and delete it ?
131. What is /etc/passwd and /etc/shadow ?
132. How do you check the disk space usage of a specific directory ?
133. How to check running processes and system resource usage ?
134. Explain the Linux boot process from pressing the power button ?
135. A server is running out of disk space. What steps do you take ?
136. How do you add a new user and provide sudo privileges ?
137. How to check the listening ports and the associated processes ?
138. How to check for deleted files still held by processes ?
139. What is the difference between “umask 022” and “umask 077” ?
140. How do we identify all world-writable files on a system ?
141. A user can’t read a file even though permissions look fine. What else would you check ?
142. We need to allow one user from a different group to write to a shared file. How can you do that ?
143. How would you restore default SELinux contexts for files after a permission change ?
144. You want to remove execute permission for all users except the owner — what command will you use ?
145.  If one apache server is running, I need to check logs? where do I check? In which directory ?
146. How do you archive and compress directory in Linux ?
147. How to configure internet gateway to route table ?
148. You want to create a persistent mount for NFS — what steps would you take?
149. What is a zombie process and how do you kill it ?
150. What is the purpose of sudo ? How is it configured ?