Unix/Linux programming interview questions and asnwers

Question 1: What is the major advantage of a hash table?
Answer: The major advantage of a hash table is its speed. Because the hash function is to take a range of key values and transform them into index values in such a way that the key values are distributed randomly across all the indices of a hash table.

Question 2: What are the techniques that you use to handle the collisions in hash tables?
Answer: We can use two major techniques to handle the collisions. They are open addressing and separate chaining. In open addressing, data items that hash to a full array cell are placed in another cell in the array. In separate chaining, each array element consist of a linked list. All data items hashing to a given array index are inserted in that list.

Question 3: In Unix OS, what is the file server?
Answer: The file server is a machine that shares its disk storage and files with other machines on the network.

Question 4: What is NFS? What is its job?
Answer: NFS stands for Network File System. NFS enables filesystems physically residing on one computer system to be used by other computers in the network, appearing to users on the remote host as just another local disk.

Question 5: What is CVS? List some useful CVS commands.
Anser: CVS is Concurrent Version System. It is the front end to the RCS revision control system which extends the notion of revision control from a collection of files in a single directory to a hierarchical collection of directories consisting of revision controlled files. These directories and files can be combined together to form a software release. There are some useful commands that are being used very often. They are
cvs checkout cvs update cvs add cvs remove cvs commit

Linux admin interview questions

1. How do you take a single line of input from the user in a shell script?
2. Write a script to convert all DOS style backslashes to UNIX style slashes in a list of files.
3. Write a regular expression (or sed script) to replace all occurrences of the letter ‘f’, followed by any number of characters, followed by the letter ‘a’, followed by one or more numeric characters, followed by the letter ‘n’, and replace what’s found with the string “UNIX”.
4. Write a script to list all the differences between two directories.
5. Write a program in any language you choose, to reverse a file.
6. What are the fields of the password file?
7. What does a plus at the beginning of a line in the password file signify?
8. Using the man pages, find the correct ioctl to send console output to an arbitrary pty.
9. What is an MX record?
10. What is the prom command on a Sun that shows the SCSI devices?
11. What is the factory default SCSI target for /dev/sd0?
12. Where is that value controlled?
13. What happens to a child process that dies and has no parent process to wait for it and what’s bad about this?
14. What’s wrong with sendmail? What would you fix?
15. What command do you run to check file system consistency?
16. What’s wrong with running shutdown on a network?
17. What can be wrong with setuid scripts?
18. What value does spawn return?
19. Write a script to send mail from three other machines on the network to root at the machine you’re on. Use a ‘here doc’, but include in the mail message the name of the machine the mail is sent from and the disk utilization statistics on each machine?
Why can’t root just cd to someone’s home directory and run a program called a.out sitting there by typing “a.out”, and why is this good?
20. What is the difference between UDP and TCP?
21. What is DNS?
22. What does nslookup do?
23. How do you create a swapfile?
24. How would you check the route table on a workstation/server?
25. How do you find which ypmaster you are bound to?
26. How do you fix a problem where a printer will cutoff anything over 1MB?
27. What is the largest file system size in solaris? SunOS?
28. What are the different RAID levels?