Saturday, August 14, 2010

Linux Interview Questions For software QA Engineers

Q: How do you display your running kernel version? (Solaris, AIX, Linux)
A: Linux # uname –r , Solaris # showrev

Q: Which command do you use to display a table of running processes? (Solaris, AIX, Linux)
A: Linux # ps –ef and top , Solaris # prstat

Q: Which file do you modify to configure a domain name resolver? (Solaris, AIX, Linux)
A: Linux # /etc/resolv.conf , Solaris # /etc/resolv.conf

Q: Which file contains a list of locally defined hostnames and corresponding IP addresses? (Solaris, AIX, Linux)
A: Linux # /etc/hosts , Solaris # /etc/hosts and linked file /etc/inet/hosts

Q: How do you display a routing table? (Solaris, AIX, Linux)
A: Linux # ip route show or #netstat –nr or #route –n and Solaris # netstat –nr and #route -n

Q: Which command would you use to view partitions and their sizes on Solaris?
A: # df -kh

Q: Which OpenBoot command would you use to print/view OpenBoot environment variables on a SUN server?
A: #printenv

Q: What does ”ypwhich” command do? (Solaris, AIX, Linux)
A: # Will display NIS server to which client is connected to and which NIS Server is master for particular map specified with this command

Q: which command would you use to create an OS user on Solaris and Linux?
A: Linux # useradd and Solaris #useradd

Q: Which file contains passwords for local users on Solaris, Linux and on AIX?
A: Linux #/etc/shadow and Solaris # /etc/shadow

Q: Which command would you use to list partitions on Linux?
A: Linux # mount –l or # df -kh

Q: Which command/commands would you use to manage installed packages on RedHat Linux?
A: Linux # rpm

Q: What is the default port for SSH server?
A: 22

Q: Which command/commands would you use to manage installed packages on Solaris?
A: #pkginfo #pkgrm # pkgadd #pkgchk

Q: What command would you use to install an OS patch on Solaris?
A: #showrev –p and #patchadd -p

Q: Which Veritas command would you use to display a list of Veritas volumes?
A: # vxprint

Q: Which Veritas command would you use to display a list of disks on a system?
A: # vxdx list

Q: What is the main system configuration utility in AIX?

Q: Which file has a list of filesystems to be mounted at boot time on Solaris, Linux and AIX?
A: Linux # /etc/fstab and Solaris #/etc/vfstab

Q: Which Veritas Cluster Server command would you use to display the status of a cluster and it’s resources?
A: clustat and to manage the cluster configruation use clusvcadm

Q: Which command would you use to rename a disk for VMware Guest virtual machine on ESX server 3 storage volume?
A: the best way is clone vm to different datastore or in the same datastore with different name
vmkfstools -i \\vmfs\old_vm.vmdk \\vmfs\new_vm.vmdk
this will take care of it all

Q: Which command would use on VMware ESX 3 server to display virtual switch configuration?
A: esxcfg-vswitch -l or user esxcfg-vswitch -help to see all options 

Software testing - Questions and Answers - Linix / Unix

1. Q. How do you list files in a directory?
   A. ls  - list directory contents
   ls �l (-l  use a long listing format)

2. Q. How do you list all files in a directory, including the hidden files?
   A. ls -a  (-a, do not hide entries starting with .)

3. Q. How do you find out all processes that are currently running?
   A. ps -f (-f does full-format listing.)

4. Q. How do you find out the processes that are currently running or a particular user?
   A. ps -au Myname   (-u by effective user ID (supports names)) (a - all users)

5. Q. How do you kill a process?
   A. kill -9  8 (process_id 8) or kill -9  %7  (job number 7)
      kill -9 -1  (Kill all processes you can kill.)
      killall - kill processes by name most (useful - killall java)

6. Q. What would you use to view contents of the file?
   A. less filename
      cat filename
      pg filename
      pr filename
      more filename
      most useful is command: tail file_name - you can see the end of the log file.

7. Q. What would you use to edit contents of the file?
   A. vi  screen editor or jedit, nedit or ex  line editor

8. Q. What would you use to view contents of a large error log file?
   A. tail  -10 file_name   ( last 10 rows)

9. Q. How do you log in to a remote Unix box?
   A. Using telnet server_name or ssh -l ( ssh - OpenSSH SSH client (remote login program))

10.Q. How do you get help on a UNIX terminal?
   A. man command_name
      info command_name (more information)

11.Q. How do you list contents of a directory including all of its
  subdirectories, providing full details and sorted by modification time?
   A. ls -lac
      -a all entries
      -c by time

12.Q. How do you create a symbolic link to a file (give some reasons of doing so)?
   A. ln /../file1 Link_name
Links create pointers to the actual files, without duplicating the contents of
the files. That is, a link is a way of providing another name to the same file.
There are two types of links to a file:Hard link, Symbolic (or soft) link;

13.Q. What is a filesystem?
   A. Sum of all directories called file system.
      A file system is the primary means of file storage in UNIX.
      File systems are made of inodes and superblocks. 

14.Q. How do you get its usage (a filesystem)?
   A. By storing  and manipulate  files.

15.Q. How do you check the sizes of all users� home directories (one command)?
   A. du -s

The du command summarizes disk usage by directory. It recurses through all subdirectories and shows disk usage by each subdirectory with a final total at the end.

   Q. in current directory
   A. ls -ps (p- directory; s - size)

16.Q. How do you check for processes started by user 'pat'?

   A. ps -fu pat   (-f -full_format u -user_name )

17.Q. How do you start a job on background?

   A. bg  %4  (job 4)

18 Q. What utility would you use to replace a string '2001' for '2002' in a text file?

   A. Grep,  Kde( works on Linux and Unix)

19. Q. What utility would you use to cut off the first column in a text file?
    A. awk, kde

20. Q. How to copy file into directory?
    A. cp  /tmp/file_name . (dot mean in the current directory)

21. Q. How to remove directory with files?
    A. rm -rf directory_name

22. Q. What is the difference between internal and external commands?
    A. Internal commands are stored in the; same level as the operating system while external
commands are stored on the hard disk among the other utility programs.

23. Q. List the three main parts of an operating system command:
    A. The three main parts are the command, options and arguments.

24  Q. What is the difference between an argument and an option (or switch)?
    A. An argument is what the command should act on: it could be a filename,
directory or name. An option is specified when you want to request additional
information over and above the basic information each command supplies.

25. Q. What is the purpose of online help?
    A. Online help provides information on each operating system command, the
syntax, the options, the arguments with descriptive information.
26.  Q. Name two forms of security.
    A.  Two forms of security are Passwords and File Security with permissions specified.

27. Q. What command do you type to find help about the command who?
    A. $ man who

28. Q. What is the difference between home directory and working directory?
    A. Home directory is the directory you begin at when you log into the
system. Working directory can be anywhere on the system and it is where you are currently

29. Q. Which directory is closer to the top of the file system tree, parent directory or current directory?
    A. The parent directory is above the current directory, so it is closer to
the root or top of the
file system.

30. Q. Given the following pathname:
$ /business/acctg/payable/supplier/april
a) If you were in the directory called acctg, what would be the relative
pathname name for the file called april?
b) What would be the absolute pathname for april?
a) $ payable/supplier/april
b) $ /business/acctg/payable/supplier/april

31. Q. Suppose your directory had the following files:
help. 1 help.2 help.3 help.4 help.O1 help.O2
aid.O1 aid.O2 aid.O3 back. 1 back.2 back.3
a) What is the command to list all files ending in 2?
b) What is the command to list all files starting in aid?
c) What is the command to list all "help" files with one character extension?
a) ls *2
b) ls aid.*
c) ls help.?

32. Q. What are two subtle differences in using the more and the pg commands?
    A.  With the more command you display another screenful by pressing
 the spacebar, with pg you press the return key.
      The more command returns you automatically to the UNIX
shell when completed, while pg waits until you press return.

33. Q. When is it better to use the more command rather than cat command?
    A. It is sometimes better to use the more command when you are viewing
 a file that will display over one screen.

34. Q. What are two functions the move mv command can carry out?
    A. The mv command moves files and can also be used to rename a file or directory.

35. Q. Name two methods you could use to rename a file.
    A. Two methods that could be used:
a. use the mv command
b. copy the file and give it a new name and then remove the original file if no longer needed.

36. The soccer league consists of boy and girl teams. The boy file names begin
with B, the girl teams begin with G. All of these files are in one directory
called "soccer", which is your current directory: Bteam.OOl Bteam.OO2 Bteam.OO4 Gteam.OOl Gteam.OO2 Gteam.OO3
Write the commands to do the following:
a) rename the file to Bteam.OO3.
b) erase the file Gteam. win after you have viewed the contents of the file
c) make a directory for the boy team files called "boys", and one for the girl team files
called" girls"
d) move all the boy teams into the "boys" directory
e) move all the girl teams into the "girls" directory
f) make a new file called Gteam.OO4 that is identical to Gteam.OOl
g) make a new file called Gteam.OO5 that is identical to Bteam.OO2
a) mv Bteam.OO3.
b) cat -or- more
rm Gteam. win
c) mkdir boys
mkdir girls
d) mv Bteam* boys
e) mv Gteam* girls
f) cd girls
cp Gteam.OO1 Gteam.OO4
g) There are several ways to do this. Remember that we are currently in the directory
cp ../boys/Bteam.OO2 Gteam.OO5
cd ../boys
cp Bteam.OO2 ../girls/Gteam.OO5

37. Q. Draw a picture of the final directory structure for the "soccer"
directory, showing all the files and directories.

38. Q. What metacharacter is used to do the following:
1.1 Move up one level higher in the directory tree structure
1.2 Specify all the files ending in .txt
1.3 Specify one character
1.4 Redirect input from a file
1.5 Redirect the output and append it to a file
1. 1.1 double-dot or ..
1.2 asterisk or *
1.3 question or ?
1.4 double greater than sign: >>
1.5 the less than sign or <

39. Q. List all the files beginning with A
    A. To list all the files beginning with A command: ls A*

40. Q. Which of the quoting or escape characters allows the dollar sign ($) to retain its special meaning?
    A. The double quote (") allows the dollar sign ($) to retain its special meaning.
Both the backslash (\) and single quote (') would remove the special meaning of the dollar sign.

41. Q. What is a faster way to do the same command?
mv fileO.txt newdir
mv filel.txt newdir
mv file2.txt newdir
mv file3.txt newdir
    A. A shortcut method would be:   mv file?.txt newdir

42. Q. List two ways to create a new file:
a. Copy a file to make a new file.
b. Use the output operator e.g. ls -l > newfile.txt

43. Q. What is the difference between > and >> operators?
    A. The operator > either overwrites the existing file (WITHOUT WARNING) or creates a new file.
The operator >> either adds the new contents to the end of an existing file or creates a new file.

44. Write the command to do the following:
44.1 Redirect the output from the directory listing to a printer.
44.2 Add the file efg.txt to the end of the file abc.txt.
44.3 The file testdata feeds information into the file called program
44.4 Observe the contents of the file called xyz.txt using MORE.
44.5 Observe a directory listing that is four screens long.
44.1 ls > lpr
44.2 cat efg.txt >> abc.txt
44.3 program < testdata
44.4 more < xyz.txt
44.5 ls > dirsave | more 

45. Q. How do you estimate file space usage
    A. Use du command (Summarize disk usage of each FILE, recursively for
directories.) Good to use arguments du -hs
(-h, --human-readable print sizes in human readable format (e.g., 1K 234M 2G)
(-s, --summarize display only a total for each argument)

46. Q. How can you see all mounted drives?
    A. mount -l

47. Q. How can you find a path to the file in the system?
    A. locate file_name (locate - list files in databases that match a pattern)

48. Q. What Linux  HotKeys do you know?
    A. Ctrl-Alt-F1 Exit to command prompt
       Ctrl-Alt-F7 or F8    Takes you back to KDE desktop from command prompt
       Crtl-Alt-Backspace Restart XWindows
       Ctrl-Alt-D Show desktop

49. Q. What can you tell about the tar Command?
    A. The tar program is an immensely useful archiving utility. It can combine
an entire directory tree into one large file suitable for transferring or

50.  Q. What types of files you know?
     A. Files come in eight flavors:
Normal files
Hard links
Symbolic links
Named pipes
Character devices
Block devices

51.  Q. How to copy files from on PC to another on the same network
     A. Use the following command:scp yur_file you_login@your_IP
example: copy .conf file from your PC  to alex computer-
 scp /etc/X11/xorg.conf alex@

52.  Q. Please describe information below:

-rw-rw-r--    1 dotpc    dotpc         102 Jul 18  2003 file.buf
drwxr-xr-x    9 dotpc    dotpc        4096 Oct 21 09:34 bin
lrwxrwxrwx    1 dotpc    dotpc          20 Mar 21 15:00 client -> client-2.9.5
drwxrwxr-x   11 dotpc    dotpc        4096 Sep  2  2005 client-2.8.9
drwxrwxr-x    7 dotpc    dotpc        4096 Dec 14 12:13 data
drwxr-xr-x   12 dotpc    dotpc        4096 Oct 21 09:41 docs
drwxr-xr-x    5 dotpc    dotpc        4096 Dec  7 14:22 etc
drwxr-xr-x   11 dotpc    dotpc        4096 Mar 21 15:54 client-2.9.5
-rw-r--r--    1 dotpc    dotpc      644836 Mar 22 09:53 client-2.9.5.tar.gz

     A. This is a result of command $ls -l
we have two files, 6 directories and one link to client-2.9.5 directory.
There is number of files in every directory, size and data of last change.

53. Q. If you would like to run two commands in sequence what operators you can use?

     A. ; or && the difference is:
if you separate commands with ; second command will be run automatically.
if you separate commands with && second command will be run only in the case
 the first was run successfully.

54.  Q. How you will uncompress the file?
      A. Use tar command (The GNU version of the tar archiving utility):
tar -zxvf file_name.tar.gz

55. Q.How do you execute a program or script, my_script in your current directoty?
    A. ./my_script

56. Q.How to find current time configuration in the file my_new.cfg
    A. grep time my_new.cfg
Grep  searches the named input files (or standard input if
no files are named, or the file name - is given) for lines
containing a match to the given pattern.

Q. What does grep() stand for?
A. General Regular Expression Parser.

57. Q. What does the top command display?
     A. Top provides an ongoing look at processor activity in real
       time.   It  displays  a  listing of the most CPU-intensive
       tasks on the system, and can provide an interactive inter­
       face for manipulating processes. (q is to quit)

58. Q. How can you find configuration on linux?
    A. by using /sin/ifconfig
If no arguments are given, ifconfig displays the  status  of  the  cur-
rently  active interfaces.  If a single interface argument is given, it displays the status of the given interface only; if a single  -a  argu-
ment  is  given,  it  displays the status of all interfaces, even those
that are down.  Otherwise, it configures an interface.

59.  Q. How to find difference in two configuration files on the same server?
     A. Use diff command that is compare files line by line
diff -u /usr/home/my_project1/etc/ABC.conf /usr/home/my_project2/etc/ABC.conf

60.  Q. What is the best way to see the end of a logfile.log file?
     A. Use tail command - output the last part of files
tail -n file_name ( the last N lines, instead of the last 10 as default)

61.  Q. Please write a loop for removing all files in the current directory that contains a word 'log'
     A. for i in *log*; do rm $i; done

62.  Question: How to switch to a previously used directory?
     Answer:   cd -

1.   Q.How many VI editor modes do you know?
     A.Three modes -
Command mode: letters or sequence of letters interactively command vi.
Insert mode: Text is inserted.
Command line mode: enter this mode by typing ":"  and entry command line  at the foot of the screen.

2.   Q. How can you terminate VI session?
  • Use command: ZZ that is save changes and quit.
  • Use command line: ":wq" that is write changes and quit.
  • Use command line: ":q!" to ignore changes and quit. 3. Q. How can you copy lines into the buffer in command mode? A. yy - copy a single line defined by current cursor position 3yy - copy 3 lines. Current line and two lines below it.
    1. Explain booting process of linux.
    2. Explain the NFS Daemons.
    3. What is the difference between soft & hard links
    4. If a  remote server having a nfs share mounted is not coming up after reboot .  What could be the problem?  How will you troubleshoot and fix it.
    5. Explain the 5th & 6th field in /etc/fstab file
    6. After an unclean shutdown of a linux box, kernel initiates file system checks on the file system(s).  From where kernel identify that the last system shutdown/reboot was unclean.
    7. What is grub.
    8. Explain the procedure to install rpm package with all dependency packages using rpm command.
    9. How to check where a particular package installed it’s configuration files
    10. How to you check status of nfs server from a client system.
    11. What is the Journaling.
    12. What are the types of Journaling.
    13. Explain difference between moduler & monolytic kernel
    14. Explain kernel compilation steps.
    15. Which file stores kernel configuration details.
    16. How to check the currently configured kernel parameters on a linux server.
    17. Explain semaphore settings
    18. How to check how much memory is used by a particular process in KB’s
    19. How to check the shared memory used by any particular application
    20. What is shared memory
    21. What is the use of shared memory
    22. What is the difference between passive & active ftp
    23. Explain setuid, setgid & sticky bit.
    24. How to check the free inodes in a file system
    25. How to  troubleshoot if the root file system space is increasing very fast in reach more than 95 %
    26. What do you mean by zombie process
    27. How will you kill the zombie processes
    28. How to check what system calls a particular script or program is executing in the background.

    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?
    20. 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?
    21. What is the difference between UDP and TCP?
    22. What is DNS?
    23. What does nslookup do?
    24. How do you create a swapfile?
    25. How would you check the route table on a workstation/server?
    26. How do you find which ypmaster you are bound to?
    27. How do you fix a problem where a printer will cutoff anything over 1MB?
    28. What is the largest file system size in solaris? SunOS?
    29. What are the different RAID levels?
    30. Advantages/disadvantages of script vs compiled program.
    31. Name a replacement for PHP/Perl/MySQL/Linux/Apache and show main differences.
    32. Why have you choosen such a combination of products?
    33. Differences between two last MySQL versions. Which one would you choose and when/why?
    34. Main differences between Apache 1.x and 2.x. Why is 2.x not so popular? Which one would you choose and when/why?
    35. Which Linux distros do you have experience with?
    36. Which distro you prefer? Why?
    37. Which tool would you use to update Debian / Slackware / RedHat / Mandrake / SuSE ?
    38. You’re asked to write an Apache module. What would you do?
    39. Which tool do you prefer for Apache log reports?
    40. Your portfolio. (even a PHP guest book may work well)
    41. What does ‘route’ command do?
    42. Differences between ipchains and iptables.
    43. What’s eth0, ppp0, wlan0, ttyS0, etc.
    44. What are different directories in / for?
    45. Partitioning scheme for new webserver. Why?

    Unix/Linux administration interview questions

    What is LILO?
    LILO stands for Linux boot loader. It will load the MBR, master boot record, into the memory, and tell the system which partition and hard drive to boot from.
    What is the main advantage of creating links to a file instead of copies of the file?
    A: The main advantage is not really that it saves disk space (though it does that too) but, rather, that a change of permissions on the file is applied to all the link access points. The link will show permissions of lrwxrwxrwx but that is for the link itself and not the access to the file to which the link points. Thus if you want to change the permissions for a command, such as su, you only have to do it on the original. With copies you have to find all of the copies and change permission on each of the copies.
    Write a command to find all of the files which have been accessed within the last 30 days.
    find / -type f -atime -30 > December.files
    This command will find all the files under root, which is ‘/’, with file type is file. ‘-atime -30′ will give all the files accessed less than 30 days ago. And the output will put into a file call December.files.
    What is the most graceful way to get to run level single user mode?
    A: The most graceful way is to use the command init s. If you want to shut everything down before going to single user mode then do init 0 first and from the ok prompt do a boot -s.
    What does the following command line produce? Explain each aspect of this line.
    $ (date ; ps -ef | awk ‘{print $1}’ | sort | uniq | wc -l ) >> Activity.log
    A: First let’s dissect the line: The date gives the date and time as the first command of the line, this is followed by the a list of all running processes in long form with UIDs listed first, this is the ps -ef. These are fed into the awk which filters out all but the UIDs; these UIDs are piped into sort for no discernible reason and then onto uniq (now we see the reason for the sort – uniq only works on sorted data – if the list is A, B, A, then A, B, A will be the output of uniq, but if it’s A, A, B then A, B is the output) which produces only one copy of each UID.
    These UIDs are fed into wc -l which counts the lines – in this case the number of distinct UIDs running processes on the system. Finally the results of these two commands, the date and the wc -l, are appended to the file “Activity.log”. Now to answer the question as to what this command line produces. This writes the date and time into the file Activity.log together with the number of distinct users who have processes running on the system at that time. If the file already exists, then these items are appended to the file, otherwise the file is created.