Interview questions 3 for Linux System Administrator

Q:16 What are the default ports used for SMTP,DNS,FTP,DHCP,SSH and squid ?

  SMTP         25
  DNS           53
  FTP            20 (data transfer) , 21 ( Connection established)
  DHCP        67/UDP(dhcp server) , 68/UDP(dhcp client)
  SSH           22
  Squid         3128


Q:17 How to check default route and routing table ?

Ans: Using the Commands ‘netstat -nr’ and ‘route -n’ we can see the default route and routing tables.


Q:18 How to check which ports are listening in my Linux Server ?

Ans:  Use the Command ‘netstat –listen’ and ‘lsof -i’


 
Q.19. How to install rpm?
 
Ans: rpm -ivh ***.rpm

 
Q20. How to add or delete a route in your System?
 
Ans: route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.254
    route del -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.254

 
Q21. How to give all permission for all user of a file?
 
    Ans: chmod 777 filename

 
Q22. How to check whether pptpd rpm installed or not?
 
     Ans: rpm -qa|grep pptpd

      Interview Questions 1 for Linux System              Interview Questions 2 for Linux System

Interview questions 2 for linux system administrator

Q:9 What is umask ?

 
Ans: umask stands for ‘User file creation mask’, which determines the settings of a mask that controls which file permissions are set for files and directories when they are created.

Q:10 How to set the umask permanently for a user?
Ans: To set this value permanently for a user, it has to be put in the appropriate profile file which depends on the default shell of the user.

Q:11 How to change the default run level in linux ?
Ans: To change the run level we have to edit the file “/etc/inittab” and change initdefault entry ( id:5:initdefault:). Using ‘init’ command we change the run level temporary like ‘init 3’ , this command will move the system in runlevl 3.

Q.12 What is SeLinux?
SELinux is an acronym for Security-enhanced Linux. It is an access control implementation and security feature for the Linux kernel. It is designed to protect the server against misconfigurations and/or compromised daemons. It put limits and instructs server daemons or programs what files they can access and what actions they can take by defining a security policy.

Q.13 Explain virtual desktop.

This serves as an alternative to minimizing and maximizing different windows on the current desktop. Using virtual desktops, each desktop is a clean slate where you can open one or more programs. Rather than minimizing/restoring all those programs as needed, you can simply shuffle between virtual desktops with programs intact in each one.

Q.14 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.

Q.15 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.

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Interview question 1 for linux system administrator

Q:1 Name the Linux services which provides network printing.

CUPS provide network printing between Linux systems. It can be used with Samba service to extend network printing to windows systems.

Q2. Which Linux service is used to provide network file storage ?

NFS service is used to provide file sharing. 

Q:3 Why LVM is required ?

Ans: LVM stands for Logical Volume Manager , to resize filesystem’s size online we required LVM partition in Linux. Size of LVM partition can be extended and reduced using the lvextend & lvreduce commands respectively.

Q:4 How To check Memory stats and CPU stats ?

Ans:  Using ‘free’ & ‘vmstat’ command we can display the physical and virtual memory statistics respectively.With the help of ‘sar’ command we see the CPU utilization & other stats.

Q:5 What is LILO?

LILO is a boot loader for Linux. It is used mainly to load the Linux operating system into main memory so that it can begin its operations.

Q:6 What is a swap space?

A swap space is a certain amount of space used by Linux to temporarily hold some programs that are running concurrently. This happens when RAM does not have enough memory to hold all programs that are executing.

Q:7 How to increase the size of LVM partition ?

Ans: Below are the Logical Steps :

– Use the lvextend command (lvextend -L +100M /dev/<Name of the LVM Partition> , in this example we are extending the size by 100MB.

– resize2fs /dev/<Name of the LVM Partition>

– check the size of partition using ‘df -h’ command

Q:8 Where the kernel modules are located ?

Ans: The ‘/lib/modules/kernel-version/’ directory stores all kernel modules or compiled drivers in Linux operating system. Also with ‘lsmod’ command we can see all the installed kernel modules.

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Interview Question for Networking Job

       10.  What are the concerns of the Physical Layer?

         Network Selection, Logical Addressing, Routing

       11.    What are the responsibilities of Transport Layer?

A end to end delivery of the entire message.
b. Segmentation and reassembly
c. Connection Control
d. Flow Control
e. Error Control

       12.     What are the responsibilities of Session Layer?

A establishes, maintains and terminate the connection
a. Dialog control
b. Synchronization

 

       13.   What are the responsibilities of Presentation Layer?

A The Presentation layer is concerned with the syntax and semantics of the information  exchanged between two systems.
a. Translation
b. Encryption
c. Compression\

 

       14.   Which layer is concerned about Application Layer?

Application Layer. FTP,TELNET,HTTP etc
  
 15. GRE works on which Layer?

Transport Layer

16. NFS works on which Layer?

Session Layer
 

Interview question for Network Engineer

      1. What will be the new subnet mask of the IP 192.168.1.1/24  if we divide it to two networks

          

               It will be 255.255.255.128

      2.    What do you call a communication system in which data cannot be sent in both directions at the same time?

         Half duplex

3.    3.    Private IP range

               Class A:- 10.0.0.1 to 10.255.255.254                    

               Class C:- 192.168.0.1 to 192.168.255.254

               Class B  :- 172.16.0.1 to 172.31.255.254

       4.   Which  devices breaks up a Broadcast Domain by default?

           Answer: Router

       5.  What is a gateway or Router?

             A Device that is connected to two or more networks is commonly called as router or    
             Gateway. It generally forwards                  message from one network to another.

      6.   What are the key elements of protocols?

            The key elements of protocols are
             a. Syntax
                It refers to the structure or format of the data, that is the order in which they are presented.
             b. Semantics
              It refers to the meaning of each section of bits.
              c. Timing
            Timing refers to two characteristics: When data should be sent and how fast they can be sent.

      7.  What is bandwidth?

             Network performance is measured in Bandwidth (throughput) and Latency (Delay). Bandwidth in a  network is the number   of bits that can be transmitted over the network in a certain period of time. In plain English it may be capacity of a link

      8.  What are the concerns of the Physical Layer?

          Physical characteristics of interfaces and media
                a. Representation of bits
                b. Data rate
               c. Synchronization of bits
               d. Line configuration
               e. Physical topology
               f. Transmission mode.

      9.  What are the concerns of the Physical Layer?

                 a Framing
                b. Physical Addressing
                c. Flow Control
                d. Error Control
                e. Access Control

10. Basically why we need to use VLAN in Switch?
      
               For increasing the number of Broadcast Domain.

Interview question for network engineer and System Engineer

      1. What types of network do you have experience with?

         

      It may be cisco or microtik or etc with which environment (linux or windows)

 

     2. What can you tell me about the OSI Reference Model?

       It provides a framework for discussing network design and operations. It groups communication  functions into 7 logical layers.

      3. What monitoring tools or approaches do you rate?

        It may be nagios, Cacti, observium, Solarwinds etc.

      4. What are the benefits of subnetting?

      Subnetting reduce the size of the routing tables. It’s also provide security to network traffic by isolating it from the rest of the network. 

       5. Why we use Tracert/traceroute command  and what protocol does it use?

         We use this command to trace the path where the problem occur and we can tell exactly where the chain of connections stop. It also use ICMP protocols like ping.

       6.  Whats the difference between Hub,Switch and Router.

         It may be “the biggest difference between hub and switch is not on the outside, but on the inside in the way that they handle connections. In the case of a hub, it broadcasts all data to every port. This can make for serious security and reliability concerns, as well as cause a number of collisions to occur on the network. Where as switch uses the table to select the port connected to destination.

       Router is different from hub and switch. It  drops the request which has no destination in routing table.

       7. What is DNS.

         It may be “ In plain English it is internet phone book. We can easily remember the name of website instead of IP address. For this we use Domain Name System.

       8. Tell Some utility tools or Programs by which we can remote login?

          It may be SSH,Telnet etc
  
       9. Router, Switch, Hub, Firewall works in which Layer. 

           Router - Layer 3.
           Switch - Layer 2.
           Hub     - Layer 1
           Firewall-Layer 3,4 

      10. Port number of ftp, ssh, telnet, dns, smtp, pop3
          
          FTP    = 21,
         SSH    = 22
         Telnet  = 23 
         dns      = 53
         smtp   = 25
         pop3   = 110
         http     = 80
        




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