Top interview question and answers for Linux administrator Part - 4

31) What is the pwd command?

The pwd command is short for print working directory command. It’s counterpart in DOS is the cd command, and is used to display the current location in the directory tree.

32) What are daemons?

Daemons are services that provide several functions that may not be available under the base operating system. Its main task is to listen for service request and at the same time to act on these requests. After the service is done, it is then disconnected and waits for further requests.

33) How do you switch from one desktop environment to another, such as switching from KDE to Gnome?

Assuming you have these two environments installed, just log out from the graphical interface. Then at the Log in screen, type your login ID and password and choose which session type you wish to load. This choice will remain your default until you change it to something else.

34) What are the kinds of permissions under Linux?

There are 3 kinds of permissions under Linux:
– Read: users may read the files or list the directory
– Write: users may write to the file of new files to the directory
– Execute: users may run the file or lookup a specific file within a directory

35) How does case sensitivity affect the way you use commands?

When we talk about case sensitivity, commands are considered identical only if every character is encoded as is, including lowercase and uppercase letters. This means that CD, cd and Cd are three different commands. Entering a command using uppercase letters, where it should be in lowercase, will produce different outputs.

36) What are environmental variables?

Environmental variables are global settings that control the shell’s function as well as that of other Linux programs. Another common term for environmental variables is global shell variables.

37) What are the different modes when using vi editor?

There are 3 modes under vi:
– Command mode – this is the mode where you start in
– Edit mode – this is the mode that allows you to do text editing
– Ex mode – this is the mode wherein you interact with vi with instructions to process a file

38) Is it possible to use shortcut for a long pathname?

Yes, there is. A feature known as filename expansion allows you do this using the TAB key. For example, if you have a path named /home/iceman/assignments directory, you would type as follows: /ho[tab]/ice[tab]/assi[tab] . This, however, assumes that the path is unique, and that the shell you’re using supports this feature.

39) What is redirection?

Redirection is the process of directing data from one output to another. It can also be used to direct an output as an input to another process.

40) What is grep command?

grep a search command that makes use of pattern-based searching. It makes use of options and parameters that is specified along the command line and applies this pattern into searching the required file output.

41) What could possibly be the problem when a command that was issued gave a different result from the last time it was used?

One highly possible reason for getting different results from what seems to be the same command has something to do with case sensitivity issues. Since Linux is case sensitive, a command that was previously used might have been entered in a different format from the present one. For example, to lists all files in the directory, you should type the command ls, and not LS. Typing LS would either result in an error message if there is no program by that exact name exist, or may produce a different output if there is a program named LS that performs another function.

42) What are the contents in /usr/local?

It contains locally installed files. This directory actually matters in environments where files are stored on the network. Specifically, locally-installed files go to /usr/local/bin, /usr/local/lib, etc.). Another application of this directory is that it is used for software packages installed from source, or software not officially shipped with the distribution.

43) How do you terminate an ongoing process?

Every process in the system is identified by a unique process id or pid. Use the kill command followed by the pid in order to terminate that process. To terminate all process at once, use kill 0.

44) How do you insert comments in the command line prompt?

Comments are created by typing the # symbol before the actual comment text. This tells the shell to completely ignore what follows. For example: “# This is just a comment that the shell will ignore.”

45) What is command grouping and how does it work?

You can use parentheses to group commands. For example, if you want to send the current date and time along with the contents of a file named OUTPUT to a second file named MYDATES, you can apply command grouping as follows: (date cat OUTPUT) > MYDATES

46) How do you execute more than one command or program from a single command line entry?

You can combine several commands by separating each command or program using a semicolon symbol. For example, you can issue such a series of commands in a single entry:

ls –l cd .. ls –a MYWORK which is equivalent to 3 commands: ls -l cd.. ls -a MYWORK

47) Write a command that will look for files with an extension “c”, and has the occurrence of the string “apple” in it.

Answer: ls -a -l *.txt

49) Write a command that will do the following:
-look for all files in the current and subsequent directories with an extension c,v
-strip the,v from the result (you can use sed command)
-use the result and use a grep command to search for all occurrences of the word ORANGE in the files.

Ans:-

Find ./ -name “*.c,v” | sed ‘s/,v//g’ | xargs grep “ORANGE”

50) What, if anything, is wrong with each of the following commands?
a) ls -l-s
b) cat file1, file2
c) ls – s Factdir

Answers:
a) there should be space between the 2 options: ls -l -s
b) do not use commas to separate arguments: cat file1 file2
c) there should be no space between hyphen and option label: ls –s Factdir

51) What is the command to calculate the size of a folder?

To calculate the size of a folder use the command du –sh folder1.

52) How can you find status of a process?

Use the command

ps ux

53) How can you check the memory status ?

You can use the command

free -m  to display output in MB

free -g  to display output in GB

54) Explain how to color the Git console?

To color the Git console  you can use the command git config—global color.ui auto.  In the command, the color.ui variable sets the default value for variable such as color.diff and color.grep.

55) How can you append one file to another in  Linux?

To append one file to another in Linux you can use command cat file2 >> file 1.  The operator >> appends the output of the named file or creates the file if it is not created.  While another command cat file 1 file 2 > file 3 appends two or more files to one.

56) Explain how you can find a file  using Terminal?

To find a file  you have to use command, find . –name “process.txt” .  It will look for the current directory for a file called process.txt.

57) Explain how you can create a folder using Terminal?

To create a folder, you have to use command mkdir.  It will be something like these :  ~$ mkdir Rohittomar007

58)  Explain how you can view the text file using Terminal?

To view the text file, go to the specific folder where the text files are located by using the command cd and then type less filename.txt.

59) Explain how to enable curl on Ubuntu LAMP stack?

To enable curl on Ubuntu , first install libcurl, once done use following command sudo/etc/init .d /apache2 restart or sudo service apache2 restart.

60) Explain how to enable root loging in Ubuntu?

The command which enables root loging is

#sudo sh-c ‘echo “greater-show-manual-login=true” >>/etc/lightdm/lightdm.conf’

61) How you can run an Linux program in the background simultaneously when you start your Linux Server?

By using nohup.  It will stop the process receiving the NOHUP signal and thus terminating it you log out of the program which was invoked with.  & runs the process in the background.

62) Explain how to uninstall the libraries in Linux?

To uninstall the libraries in Linux, you can use command  sudo apt – get remove library_name