Linux Interview Questions

Linux Interview Questions:

1. How can you determine the space left in a file system? 

Level: Low 

Expected answer: There are several commands to do this: du, df, or bdf 

2. How can you determine the number of SQLNET users logged in to the UNIX system? 

Level: Intermediate 

Expected answer: SQLNET users will show up with a process unique name that begins with oracle, if you do a ps -ef|grep oracle|wc -l you can get a count of the number of users.

3. What command is used to type files to the screen? 

Level: Low 

Expected answer: cat, more, pg 

4. What command is used to remove a file? 

Level: Low 

Expected answer: rm 

5. Can you remove an open file under UNIX? 

Level: Low 

Expected answer: yes 

6. How do you create a decision tree in a shell script? 

Level: intermediate 

Expected answer: depending on shell, usually a case-esac or an if-endif or fi structure 

7. What is the purpose of the grep command? 

Level: Low 

Expected answer: grep is a string search command that parses the specified string from the specified file or files 

8. The system has a program that always includes the word nocomp in its name, how can you determine the number of processes that are using this program?

Level: intermediate 

Expected answer: ps -ef|grep *nocomp*|wc -l 

9. What is an inode? 

Level: Intermediate 

Expected answer: an inode is a file status indicator. It is stored in both disk and memory and tracts file status. There is one inode for each file on the system.

10. The system administrator tells you that the system hasn?t been rebooted in 6 months, should he be proud of this? 

Level: High 

Expected answer: Maybe. Some UNIX systems don?t clean up well after themselves. Inode problems and dead user processes can accumulate causing possible performance and corruption problems. Most UNIX systems should have a scheduled periodic reboot so file systems can be checked and cleaned and dead or zombie processes cleared out.

11. What is redirection and how is it used? 

Level: Intermediate 

Expected answer: redirection is the process by which input or output to or from a process is redirected to another process. This can be done using the pipe symbol "|", the greater than symbol ">" or the "tee" command. This is one of the strengths of UNIX allowing the output from one command to be redirected directly into the input of another command.

12. How can you find dead processes? 

Level: Intermediate 

Expected answer: ps -ef|grep zombie -- or -- who -d depending on the system. 

13. How can you find all the processes on your system? 

Level: Low 

Expected answer: Use the ps command 

14. How can you find your id on a system? 

Level: Low 

Expected answer: Use the "who am i" command. 

15. What is the finger command? 

Level: Low 

Expected answer: The finger command uses data in the passwd file to give information on system users. 

16. What is the easiest method to create a file on UNIX? 

Level: Low 

Expected answer: Use the touch command 

17. What does >> do? 

Level: Intermediate 

Expected answer: The ">>" redirection symbol appends the output from the command specified into the file specified. The file must already have been created.

18. If you aren?t sure what command does a particular UNIX function what is the best way to determine the command? 

Expected answer: The UNIX man -k command will search the man pages for the value specified. Review the results from the command to find the command of interest.