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Scenario Based Linux Interview Questions & Answers

Scenario based Linux Interview Questions & Answers

These are some of the consolidated real scenario based linux interview questions and answers.

1. An application is creating several, very large core dump files. What should the administrator do if he has no intention of debugging these files?
If administrator have no intention of keeping these files for debugging purposes, they should be deleted because they are wasting valuable disk space, and may cause system to run out of space.

2. What sort of kernel error can cause a Linux system to crash and write a memory core dump?
Kernel panic error can cause a Linux system to crash. A kernel panic indicates that a kernel process has crashed. This is a very serious error that causes the entire Linux system to crash. These core dumps should be analyzed carefully to find the root cause of the problem.

3. As a administrator you may need to terminate some process. For example lets say the sendmail process. How will you kill the process?
First you need to determine the PID of sendmail so it can be killed.
#ps -ef |grep sendmail
Now you can use kill command to terminate the process associated with sendmail.

Also refer more interview questions and answers,
Veritas Cluster Interview Questions and Answers
Linux Interview Questions and Answers
Openstack Interview Questions and Answers
Vmware Interview Questions and Answers
Cluster Interview Questions and Answers
HR Interview Questions and Answers

4. You noticed a kernel error message during the boot process, but it scrolled before you could read this? What log file could you check to find out that message?
The log file that contains kernel boot messages is /var/log/dmesg.

5. You execute a command that is going to take a long time. How can you get back to your shell prompt to perform other task?
You can use bg command to send a running process to the background.

6. You need to kill all instances of Web Server? What command will you execute to do this?
You can use killall httpd command to kill all httpd process. httpd process run web server.

7. How can you list all running process?
Use ps -ef command to list all running process.
#ps -ef

8. As a Linux admin you want to know what processes are being run by user sumit. What command can you use ?
You can use #ps -au command to list all the process owned by user. Following command will do the assigned task.
#ps -au sumit


9. Which log file keeps track of all user logins and logouts?
/var/log/wtmp log file keeps track of all user logins and logouts.

10. What is the first process that is run when a Linux system starts, and is responsible for starting all other system processes and services?
The init process is the first process to be run. It is the parent process of all other Linux system processes, services, and daemons that are needed to run the system.

11. An administrator has accidentally killed a core process. What is the result of this action?
Killing a core process can potentially crash your system because many critical services rely on these core processes

12. As a administrator you need to monitor the /var/log/messages file in real time to resolve the issue? How would you do that?
You can use tail command with -f option. Following command will do the assigned task
#tail -f /var/log/messages

13. From the output of ps command how will you determine the ID number of the parent process of a particular program?
PPID refers to the parent process identification number.

14. While scanning the /var/log/messages file, you notices an error stating an authentication failure for root. What could this mean?
Any failed login attempts for root are logged into the /var/log/messages file. It indicate that some one has tried to login as root.

15. As an administrator you noticed from top command that an unidentified process is using up all CPU and memory. You suspects that is a user's process that has run away. How should you fix this ?
The process should be immediately killed before it consumes so many resources that the server cannot run properly, and therefore crash.

16. What command can an administrator use to track real-time information on processes and the resources that they are using?
The top command is used to monitor processes and resources in real-time.

17. Why should you periodically update the kernel and package versions?
To enhance the security of system you should ensure that you are using the latest versions kernel and software packages that contain the most recent security updates.

18. During a recent strikes at office, several archive tapes of the system were damaged and ruined. What can you do to prevent the physical damage in future?
You should store them at offsite.

19. Why should you avoid the Telnet to administer a Linux system remotely?
Telnet use most insecure method for communication. It send data across the network in plain text format. Someone easily find out the password using the network tool.

20. Your company hire a contract employee for two months. What should the Linux administrator do to enhance security on the employee's account?
While creating new user account for this user, administrator should set the expiration date for his account, so that if the employee leaves or does not have their contract renewed, the account will be automatically disabled.

21. A user complains you that he is unable to set '123' as his password. Why would not the system allow this password?
There would be a minimum length rule for password, which is blocking user to use this password. Default minimum length rule for password is six characters. It means a user cannot have password less than six characters.

22. 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?
You should remove / comment the "Options Indexes" directive from the main configuration file ' httpd.conf' of the web server. 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.

23. How can you enhance the security of password file?
Linux keep user account information in a text file called /etc/passwd. This file also store one way encrypted password. This file is accessed by several tools to get user information, so file need to world readable. This is a security risk. To minimize the security risk you can use shadow password format. This method save account information in regular file /etc/passwd. However, the password is stored as a single "x" character (not actually stored in this file). A second file, called "/etc/shadow", contains encrypted password as well as other information such as account or password expiration values, etc. The /etc/shadow file is readable only by the root account and is therefore less of a security risk

24. You have just finished the installation of sever. This server is going to be use as file server. Default installation have send mail service running, while this server will never send any e-mails. How should you deal with send mail service?
You should disable the send mail service if server is not being used for mail purpose. Leaving them running can increase the chance of a security vulnerability being exploited, and unauthorized use of sendmail relay.

25. Which necessary steps should you take to enhance the security of server just after the initial installation?
Kernel and packages should be upgraded to the latest versions.
Unnecessary services and daemons should be disable.
Enable and configure firewall
Set a complex password policy.

26. You are setting up an FTP server. Only company employees are allowed to use the FTP services. What should you configure on the FTP server to enhance security?
You should disable the anonymous FTP account, so that only users with a username and password can access the system.

27. What is the location of system configuration files that should be backed up on a regular basis?
The /etc directory contains most of the Linux system configuration files.

28. Due to power fluctuation, your system starts up from a powered off state. You receive a warning error stating that the machine was not shut down properly, and fsck will be run. What is the cause of this message?
If your hard drive file systems are not unmounted properly, the fsck utility will automatically run the next time the system is started to fix any inconsistencies before they are mounted again. If they are not fixed, the file system can quickly become corrupt.

29. When you try to boot a Linux system, you receive a message stating that it cannot mount the /home partition because of errors. While debugging , you found that it occur due to data error. What can you do to fix the problem?
You can use fsck utility that enable you to recover from the errors.

30. During a software package installation, an error occurs warning that a certain library is missing, and the installation aborts. What is the most likely cause of the problem?
Many software packages are dependent on other programs to function properly. If these dependencies do not exist, you must install them before installing your software package or install the package using yum to avoid dependency issues.

Also refer more interview questions and answers,
Veritas Cluster Interview Questions and Answers
Linux Interview Questions and Answers
Openstack Interview Questions and Answers
Vmware Interview Questions and Answers
Cluster Interview Questions and Answers
HR Interview Questions and Answers
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