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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OSPF EIGRP Redistribution

R2#show interface s0/0/0

Write down these 5 parameters, notice that we have to divide the Delay by 10 because the metric unit is in tens of microsecond. For example, we get Bandwidth=1544 Kbit, Delay=20000 us, Reliability=255, Load=1, MTU=1500 bytes then we would redistribute as follows:

R2#config terminalR2(config)# router ospf 24
R2(config-router)# redistribute eigrp 100 metric-type 1 subnetsR2(config-router)#exitR2(config-router)#router eigrp 100R2(config-router)#redistribute ospf 24 metric 1544 2000 255 1 1500

R3#show interface fa0/0

For example we get Bandwidth=10000 Kbit, Delay=1000 us, Reliability=255, Load=1, MTU=1500 bytes

R3#config terminal
R3(config)#router ospf 34
R3(config-router)#redistribute eigrp 100 metric-type 1 subnets
R3(config)#exit
R3(config-router)#router eigrp 100
R3(config-router)#redistribute ospf 34 metric 10000 100 255 1 1500

OSI Layer tutorial

    Introduction to OSI Layer


In the beginning the development of networks the bad part was that one vendor’s solution was not compatible with another vendor’s solution. This is where the idea for the OSI model was born, having a layered approach to networks our hardware vendors would design hardware for the network, and others could develop software for the application layer. Using an open model which everyone agrees on means we can build networks that are compatible with each other.


To fix this problem the International Organization for Standardization (ISO) researched different network models and the result is the OSI-model which was released in 1984.

Layers are :


Layer 7 – Application layer

This is the closest layer to the end user. It provides the user interface between the applications.  Telnet, FTP, email client (SMTP), HyperText Transfer Protocol (HTTP) are examples of Application layer.


Layer 6 – Presentation layer

 This layer ensures the presentation of data, that the communications passing through are in the appropriate form for the recipient. In general, it acts as a translator of the network.

Character code translation: for example, ASCII to EBCDIC.

Data conversion: bit order, CR-CR/LF, integer-floating point, and so on.

Data compression: reduces the number of bits that need to be transmitted on the network.

Data encryption: encrypt data for security purposes. For example, password encryption.


Layer 5 – Session layer

Layer 5 establishes, maintains and ends communication with the receiving device.


Layer 4 – Transport layer

 Data is reffered here as a segment. This layer maintains flow control of data and provides for error checking and recovery of data between the devices. The most common example of Transport layer is Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). Data is reffered here as a segment


Layer 3 – Network layer

  Data is reffered here as a packet. This layer provides logical addresses which routers will use to determine the path to the destination. In most cases, the logic addresses here means the IP addresses (including source & destination IP addresses).


Layer 2 – Data Link Layer

Data is reffered here as a frame. The Data Link layer formats the message into a data frame, and adds a header containing the hardware destination and source address to it. This header is responsible for finding the next destination device on a local network.

Notice that layer 3 is responsible for finding the path to the last destination (network) but it doesn’t care about who will be the next receiver. It is the Layer 2 that helps data to reach the next destination.

This layer is subdivide into 2 sub-layers: logical link control (LLC) and media access control (MAC).

The LLC functions include:

+ Managing frames to upper and lower layers
+ Error Control
+ Flow control

The MAC sublayer carries the physical address of each device on the network. This address is more commonly called a device’s MAC address. MAC address is a 48 bits address which is burned into the NIC card on the device by its manufacturer.

Layer 1 – Physical layer

Data is send here as a bit. The Physical Layer defines the physical characteristics of the network such as connections, voltage levels and timing.

Database basic questions part 1

DDL

Data Definition Language (DDL) statements are used to define the database structure or schema. Some examples:

• CREATE - to create objects in the database
• ALTER - alters the structure of the database
• DROP - delete objects from the database
• TRUNCATE - remove all records from a table, including all spaces allocated for the records are removed
• COMMENT - add comments to the data dictionary
• RENAME - rename an object

DML

Data Manipulation Language (DML) statements are used for managing data within schema objects. Some examples:

• SELECT - retrieve data from the a database
• INSERT - insert data into a table
• UPDATE - updates existing data within a table
• DELETE - deletes all records from a table, the space for the records remain
• MERGE - UPSERT operation (insert or update)
• CALL - call a PL/SQL or Java subprogram
• EXPLAIN PLAN - explain access path to data
• LOCK TABLE - control concurrency

DCL

Data Control Language (DCL) statements. Some examples:

• GRANT - gives user's access privileges to database
• REVOKE - withdraw access privileges given with the GRANT command

TCL

Transaction Control (TCL) statements are used to manage the changes made by DML statements. It allows statements to be grouped together into logical transactions.

• COMMIT - save work done
• SAVEPOINT - identify a point in a transaction to which you can later roll back
• ROLLBACK - restore database to original since the last COMMIT
• SET TRANSACTION - Change transaction options like isolation level and what rollback segment to use

Trigger : 
    A database trigger is procedural code that is naturally executed in light of specific occasions on a specific table or view in a database. The trigger is generally utilized for keeping up the uprightness of the data on the database. For instance, when another record (speaking to another laborer) is added to the workers table, new records ought to likewise be made in the tables of the charges, get-aways and pay rates. Triggers can likewise be utilized to log recorded information, for instance to monitor representatives' past compensations 

RDMS 

     RDBMS Database is a relational database. It is the standard dialect for relational database administration systems.Data is put away as lines and segments in RDBMS. The relations among tables are additionally put away as the table SQL (Structured quiry Language) is a programming Language used to perform undertakings, for example, refresh information on a database, or to recover information from a database. Some normal relational database administration frameworks that utilization SQL are: Oracle, Sybase, Microsoft SQL Server, Access, and so on.

 Schema
   
    A database schema is a approach to logically group objects such as tables, views, stored procedures etc. Think of a schema as a container of objects.You can assign a user login permissions to a single schema so that the user can only access the objects they are authorized to access.

Schemas can be  made and modified in a database, and users can be granted access to a schema. A schema can be owned by any user, and schema ownership is transferable. 

What will we do for getting Job in IT Sector.

What will we do for getting Job in IT Sector.

This article is for them who is searching for IT Jobs. There are some field in IT segment where we need to pick just a single of those. The Fields are

1. Programming/Developing
2. Database Administrator
2. Network Engineer
4. System Engineer
5. Hardware Engineer

Nobody is accessible who is master in the greater part of the fields. We discover inquiries of all subject or field in IT related occupation exam. It is affirm that he can not do well in systems administration who can do well in database or he can do well in programming who can not do well in hardware part. Be that as it may, he will be succeed who does well at least 2 or more than 2 fields. Its not suggested that he will be solid in networking who is solid in programming. Yet, I propose those software engineer who isn't intrigued to other field to do well in any of those field and it will be better for him in the event that he learn database too.

I can share my experience of pubali bank job exam. There were 100 questions in that exam where 80 was on IT and rest of the questions were on English. These 80 marks was separated in severel field.

Programming 10
Database 10
Information Structure and Algorithm 10
Systems administration 20
Linux System 15
Hardware,testing and others 15

I have done more well in Networking and Linux System. I had taken some fundamental thought of Database like DDL,DML,DCL,TCL, some essential query,table joining and so forth and Data Structure and Algorithm and so on. So I mostly  covered these field and after all I got opportunity to join there. I have discovered same kind of questions in Rupali bank, Janata Bank. Presently we see some general knowledge and also math in Bank exam. So we will read increasingly and take in more and finaly be allowed in exam InshahAllah.

Have a good journey.

Static vs Dynamic Routing

In static routing, network administrator manually enters entries to the routing tables. But in dynamic routing, network administrator does not have to enter any entries as the entries are auto generated.

• For static routing, the action is to just do a lookup on a table and hence does not need any processing making the hardware less costly. But, dynamic routing algorithms involves a lot of calculations. Hence, it requires much processing capabilities. As a result, the hardware would be costly. 

 In dynamic routing, routing entries are generated using complex routing algorithms. In static routing, no such algorithms are involved.

• In static routing, routers do not advertize or broadcast any information about the links to other routers. But, in dynamic routing, tables are generated using such information advertised by routers.
In static Routing need to set destination network in routing table with gateway.
 

   Router configuration( Static Routing):
   
   R1
   ******
   #configure terminal
   #ip route 192.168.3.0 255.255.255.0 192.168.2.2

   R2
   ******
   #configure terminal
   #ip route 192.168.1.0 255.255.255.0 192.168.2.1

   Router configuration( Dynamic Routing RIP):
   R1
   ******
   #configure terminal
   #router rip
   #version 2
   #network 192.168.1.0   
   #network 192.168.2.0

   R2
   ******
   #configure terminal
   #router rip
   #version 2
   #network 192.168.3.0
   #network 192.168.2.0

In Dynamic Routing We just entry the connected network to share with other router.

In Dynamic Routing no need to set destination network in routing table. Dynamic Routing Protocols
help the network administrator manage the time-consuming and exacting process of configuring and
maintaining static routes.

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.