Top 20 Linux Interview Questions For Experienced SysAdmins

Job change is not easy now a days, there are multiple procedure you have to face and cleared them to enter into next round. Technical interview is one of them. For Experienced System Administrator, technical interview is not so easy. One must know all about handing all infra and new tools and technology. Here we consolidated top 20 linux interview questions for experienced sysadmins. Just go through them and you will feel more confident during interviews.

Que:1. What are the necessary steps you should take to enhance the security of server just after the initial installation?

Ans: Just after installation of any linux system, you have to configure it to overcome security threats. You need to follow below steps to enhance the security.

  • Kernel and packages should be upgraded to the latest versions.
  • Unnecessary services and daemons should be disable.
  • Enable and configure firewall.
  • SELinux Should be in enforcing mode.
  • Set a complex password policy.

Que:2. During the bootup of a Linux system, there is no output on the monitor, the machine beeps, and then halts the boot-up process. What is the most likely cause of the problem? 

Ans: If the system would not even get to the POST stage, the problem is most likely with the motherboard itself. You should count and compare the number of beeps to the BIOS manual in order to determine which specific component failed.

Que:3. Which utility should be used to repair the corrupted file system?

Ans: fsck utility can be used to repair the corrupted file system.

Que:4. What must you do before performing fsck on a file system?

Ans: The fsck utility can be used only on a file system that is in unmounted state. If it were active, fsck would not be able to properly repair the drive, and may cause further corruption.

Que:5. As a Linux administrator, you want to review the messages that scrolled up the screen during a system boot. How can this be accomplished? 

Ans: The boot kernel messages are saved to the log file /var/log/dmesg. We can check this file.

Que:6. A user complains you that his system was running fine, before he rebooted. When it starts up, no display appears on the screen and the system is beeping. What may cause this?

Ans: As the system was running fine before reboot and during the reboot it got a problem even before the operating system is loaded, the problem is hardware-based, and is most likely caused by a problem with the motherboard.

Que:7. A user can not access a remote server. Which command can be used to verify that the remote server is up & running?

Ans: The user can use ping command to check whether remote server is up or not.

Que:8. You are tasked to examine a log file in order to find out why a particular application keep crashing. Log file is very lengthy, which command you can use to simplify the log search using a search string?

Ans: We can use grep command to output the log file. We can specify the keyword of desired application to look for, grep command than displays all instances of that word in log file.

Que:9. An application process has just failed on a Linux system. What should you examine first to find out the root of the problem? 

Ans: When any application fails, the first thing you should do to troubleshoot the problem is to examine the application logs to get the particular error that caused the application to fail.

Que:10. During a software package installation, an error occurs with warning that a certain library is missing, and the installation aborts. What is the most likely cause of the problem?

Ans: Many software packages are dependent on other programs to function properly. If these dependencies do not exist, then you may get warning and installations would not finish. You must install these dependencies before installing that particular software package.

Que:11. What command should be used to show the first 100 lines of a file?

Ans: The command to show the first 100 lines of a file is head -100 filename.

Que:12. Can you configure KVM Virtual machine on 32 bit system?

Ans: No, KVM virtualization requires at least 64 bit system.

Que:13. Why should you periodically update the kernel and package versions?

Ans:  To enhance the security of a system, you should ensure that you are using the latest kernel version and software packages that contain the most recent security updates.

Que:14. Why should you avoid the Telnet to administer a Linux system remotely?

Ans: Telnet uses most insecure method of communication. It sends data across the network in plain text format. Anyone could easily find out the password using the network tool.

Que:15. Your FTP Server is recently hacked. Due to the amount of damage, the entire server needs to be restored. How would you accomplish this?

Ans: You cannot restore the entire operating system from tape backup device. So you should reinstall the core operating system, and then restore system configuration files and user data from tape backup device.

Que:16. A newbie enabled the root session for FTP server. is it ok?

Ans: No, he has put the security of entire server on risk. You should disable to root session as soon as possible.

Que:17. What is the name of the service which should be disabled on a Linux Server which is acting as both a Web and FTP Server?

Ans: The finger service should be disabled because a remote user can get important information about the system by using that command.

Que:18. Your company hire a contract employee for two months. What should the Linux administrator do to enhance security on the employee’s account?

Ans: While creating a new user account, the administrator should set the expiration date for this account so that if the employee leaves or does not have their contract renewed, the account will be automatically disabled.

Que:19. Your company is running Web Server. One dedicate account holder customer complains that his visitors are able to scan the directory tree. Which directive would you configure to stop web server from listing the directory?

Ans: Directory index listings are disabled by default, if they were previously enabled so you need to explicitly disable them in .htaccess file. To do this, use a text editor to modify the Options line in the .htaccess file as follows:

Options -Indexes

This is a security measure so that remote users can’t scan the directory tree of the server looking for security holes. Server won’t show directory listings if requested by a user.

Que:20. A junior system administrator is trying to read through a large log file using the cat command. Because it is so large, the cat command scrolls the file right to the end without allowing the start of the file to be read. What command can he be used to more easily read the file?

Ans: He can use less command instead of cat command which allows him to scroll through the log file.

Hence, you have gone through the mostly asked top 20 linux interview questions for experienced sysadmins during interviews. I hope you are feeling more confident now. This is a series of Linux Interview Questions. This was the Part One. You will see more soon, so stay tuned. Thanks!!

Read Also : Top 20 Linux Interview Questions for Freshers


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Ravindra Kumar

Hi, This is Ravindra. I am founder of TheCodeCloud. I am AWS Certified Solutions Architect Associate & Certified in Oracle Cloud as well. I am DevOps and Data Science Enthusiast.

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