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xterm

Provides a terminal emulator for the X Window System. Note: The xterm command is ported from the Massachusetts Institute of Technology (MIT) X Window System, Version 11, Release 6 with no functional enhancements. The xterm command does not have support for globalization. For the localized and internationalized terminal emulator, the user can use the aixterm  Full Article…

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ntpq

ntpq – standard NTP query program   The ntpq utility program is used to monitor NTP daemon ntpd operations and determine performance. The program can be run either in interactive mode or controlled using command line arguments. Type the following command $ ntpq -pn OR $ ntpq -p Sample outputs: remote refid st t when  Full Article…

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Install RHEL 7.2

Red Hat Enterprise Linux (RHEL) is a Linux operating system developed by Red Hat. RHEL is mainly aimed at commercial organisations. Red Hat Enterprise Linux is available for multiple platforms including x86, x86_64, PowerPC, IBM pSeries and IBM System z (Mainframe). RHEL 7.2 is the latest version available from Red Hat (released November 2015). RHEL  Full Article…

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GARP Generic Attribute Registration Protocol

GARP (Generic Attribute Registration Protocol) is a local area network (LAN) protocolthat defines procedures by which end stations and switches can register and de-register attributes, such as network identifiers or addresses, with each other. Every end station and switch thus has a record, or list, of all the other end stations and switches that can  Full Article…

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How to Install an SSL Certificate

An SSL Certificate is a text file with encrypted data that you install on your server so that you can secure/encrypt sensitive communications between your site and your customers. After you create a CSR (certificate signing request) and purchase a certificate, our Validation team validates and processes your certificate request. Once validated, we issue your  Full Article…

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What does RSA stand for?

RSA encryption is a public-key encryption technology developed by RSA Data Security. The RSA algorithm is based on the difficulty in factoring very large numbers. Based on this principle, the RSA encryption algorithm uses prime factorization as the trap door for encryption. Deducing an RSA key, therefore, takes a huge amount of time and processing  Full Article…

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VMware Admin Interview Questions & Answers.

1. VMWare Kernel is a Proprietary Kenral and is not based on any of the UNIX operating systems, it’s a kernel developed by VMWare Company. 2. The VMKernel can’t boot it by itself, so that it takes the help of the 3rd party operating system. In VMWare case the kernel is booted by RedHat Linux  Full Article…

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Top 15 VMWare Interview Questions

1) Mention what is VMware and what are their benefits? VMware provides different applications and software for virtualization.  VMware products are categorized in two levels, desktop applications, and Server applications.  It is useful for Running multiple operating systems and applications on a single computer Consolidate hardware to get vastly higher productivity form fewer servers Save  Full Article…

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VMWare Administrator Interviews

VMware Administrator Levels:   Level 1 Engineers:  Fresher’s or newbie to VMware Level 2 Engineers:  Experienced VMware administrators   Level 1 Engineers:  Fresher’s or newbie to VMware   It’s essential to be prepared with some basic OS, domain, Servers, Network and other technological or conceptual level questions as all these are required to build any  Full Article…

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100 REAL TIME VMWARE interview Questions and Answers List of top 100 vmware interview questions and answers,vmware tutorials for freshers beginners and experienced pdf free download. vmware interview Question

List of top 100 vmware interview questions and answers,vmware tutorials for freshers beginners and experienced pdf free download. vmware interview Questions and Answers :- 1. What is VMware and what are their Uses? 2. What is HA? 3. What are the different types of server software does VMware provides? vmware interview Questions and Answers 22.  Full Article…

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Interview Questions on VMware ESXi with Answers

What is a Hypervisor? It is a program that allows multiple operating systems to share a single hardware host. Each operating system appears to have the host’s processor, memory, and other resources all to itself. However, the hypervisor is actually controlling the host processor and resources, allocating what is needed to each operating system in  Full Article…

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How BGP works

You need to understand that what follows is a gross simplification of BGP so you have to take it that way. BGP is actually very similar to RIP. In its core, just like RIP, it learns routes from different neighbors (in BGP called peers), adds its own routes, decides what path toward a particular destination  Full Article…

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Understanding RIP Routing

RIP, like all routing protocols, is designed to disseminate network information pertinent to routers. At the most basic level, routers need to know what networks are reachable and how far away they are. RIP does this, and it’s still widely used today. Remember, we said that RIP is a distance-vector protocol. The distance part is  Full Article…

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Understanding OSPF Routing

Open Shortest Path First is a robust link-state interior gateway protocol (IGP). People use OSPF when they discover that RIP just isn’t going to work for their larger network, or when they need very fast convergence. To understand the design needs for areas in OSPF, let’s start by discussing how OSPF works. There’s some terminology  Full Article…

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BGP Routing

The Border Gateway Protocol (BGP) is the routing protocol of the Internet, used to route traffic across the Internet.   BGP is the path-vector protocol that provides routing information for autonomous systems on the Internet via its AS-Path attribute. BGP is a Layer 4 protocol that sits on top of TCP. It is much simpler  Full Article…

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Basic Interview Questions and Answers

VMWare Top Interview Questions with Answers 1) Explain about your production environment? How many cluster’s, ESX, Data Centers, H/w etc ? 2) How does VMotion works? What’s the port number used for it? ANS–> TCP port 8000 3) Prerequisites for VMotion? Ans–> 1)ESX Servers must be configured with VMkenerl ports enabled for vmotion and on  Full Article…

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Top 50 VMware vSphere Interview Questions Answers

Explain what is VMware? VMware, Inc. is an American company that provides cloud and virtualization software and services, and claims to be the first to successfully virtualize the x86 architecture commercially. Founded in 1998, VMware is based in Palo Alto, California. What is virtualization? Virtualization is a proven software technology that makes it possible to  Full Article…

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01.0.1 Environment Variables, Aliases And Shell Configuration Files

01.0.1 Environment Variables, Aliases And Shell Configuration Files customize comand prompt global configuration file is inside /etc /etc/ bash.bashrc apply to anyuser   export EDITOR=”vi” export EDITOR=”nano” echo $EDITOR echo $PS1 export PS1=”\[\u@awesome]$”   global configuration file inside etc/ vi  bash.basrc   01.02. Modifying Bash Shell Configuration Files or profile.d/ bash folder/ ls | grep  Full Article…

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linux-sysadmin-interview-questions-1

Using the OSI model, which layer has the responsibility of making sure that the packet gets where it is supposed to go? What is the subnet mask, network address and broadcast address for the following address: 123.65.47.62/22? What command is used to show all open ports and/or socket connections on a machine? What is NAT?  Full Article…

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Number of Processes

ps ax | wc -l | tr -d ” ” OR ps ax | wc -l | awk ‘{print $1}’ OR ps ax | wc -l | sed -e “s: ::g”. In each case, tr or awk or sed is used to remove the undesirable whitespace. Relative speed: any one of these variants takes about  Full Article…

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Total Bytes in the Current Directory

If you want to know how much space the contents of the current directory take up, you can use something like the following: let TotalBytes=0 for Bytes in $(ls -l | grep “^-” | awk ‘{ print $5 }’) do let TotalBytes=$TotalBytes+$Bytes done # The if…fi’s give a more specific output in byte, kilobyte, megabyte,  Full Article…

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Cloning an Encrypted Ubuntu System

Creating a System Clone: Overview So, to create a clone of an existing installed system, one simply needs to recreate the above configuration, copy all of the files to it, change some configuration files (particularly those dealing with the UUIDs of the filesystems), and make sure that grub and the initrd images are configured properly.  Full Article…

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linux clone encrypted drive to smaller drive

I’m going to answer the question myself, but a general note: Maybe its fastest just to start from scratch, the steps are complicated and timeconsuming! Make Backup using your favourite disk cloning/backup tool Follow the Ubuntu Wiki Article about ResizeEncryptedPartions Make sure the partitions matches exactly the size of your smaller disk (so the free  Full Article…

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What is noatime and how does it work?

Linux records information about when files were created and last modified as well as when it was last accessed. There is a cost associated with recording the last access time. ext2/ext3 file systems have an attribute that allows the super-user to mark individual files such that their last access time is not recorded. This may  Full Article…

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What are the process states in Unix?

As a process executes it changes state according to its circumstances. Unix processes have the following states: Running* : The process is either running or it is ready to run . Waiting* : The process is waiting for an event or for a resource. Stopped* : The process has been stopped, usually by receiving a signal. Zombie* : The  Full Article…

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How to Setup network on centos 7

Setup network on centos 7 let’s start, Type “nmcli d” command in your terminal for quick identification of Ethernet cards installed in your machine. Here we have 2 interfaces named “enp0s17” and “enp0s18” . it might be different in your case ( Eg: em1 or p4p1 ). GUI Mode Recommended for beginners Step 1 »  Full Article…

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What is Dead Lock

Dead-Lock is occurred in multiple users Computing Environment. As we know that there is Many Number of users those are going to perform their Transactions. Dead-Lock has occurred when two or More Users are requesting for data item or for a Resource of System for example two or more users Request for the Printers at  Full Article…

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Differentiate between RAM and ROM?

RAM: Read / Write memory, High Speed, Volatile Memory. ROM: Read only memory, Low Speed, Non Voliate Memory. 1. When power is lost or turned off, a ROM chip will keep the information stored on it. In contrast, a RAM chip is volatile and requires a constant source of power to retain information. 2. A  Full Article…

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What is cache memory?

Cache memory is a small high-speed memory. It is used for temporary storage of data & information between the main memory and the CPU (center processing unit). Thecache memory is only in RAM.

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TCP Three way handshake

The TCP three-way handshake in Transmission Control Protocol (also called the TCP-handshake; three message handshake and/or SYN-SYN-ACK) is the method used by TCP set up a TCP/IP connection over an Internet Protocol based network. TCP’s three way handshaking technique is often referred to as “SYN-SYN-ACK” (or more accurately SYN, SYN-ACK, ACK) because there are three  Full Article…

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What is boot strap protocol

The Bootstrap Protocol (BOOTP) is a computer networking protocol used in Internet Protocol networks to automatically assign an IP address to network devices from a configuration server. The BOOTP was originally defined in RFC 951. BOOTP was largely replaced by the more efficient Dynamic Host Configuration Protocol (DHCP), which has more options and flexibility. However,  Full Article…

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IPTABLES  Interview Questions 

How to disable IPTABLES ? ================== # service iptables save # service iptables stop # chkconfig iptables off How To clear IP rules in IPTABLES use below commands: ===================================== # iptables -F # iptables -X # iptables -t nat -F # iptables -t nat -X # iptables -t mangle -F # iptables -t mangle -X  Full Article…

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YUM Interview Questions and Answers

1.What is yum  ? Answer: yum is “yellow update manager” which is a front end tool for package management. All the rpm commands activity can be carried out using yum command in automated way. Yum mechanism will automatically resolve the dependencies unlike rpm commands. 2.How to install packages using yum ? Answer:yum install package_name 3.How  Full Article…

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LDAP Server Interview Questions And Answers

Q 1 : – Is there Graphical editors for LDAP ? Yes, Following are some GUI based tools for LDAP – GQ – Java LDAP Browser/Editor – Softerra LDAP Browser Q 2 : – What can i do if my application doesn’t speak to LDAP ? Gateway that translate one directory access protocol into another.  Full Article…

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Apache Interview Questions

1) What’s the command to stop Apache? kill the specific process that httpd is running under, or killall httpd. If you have apachectl installed, use apachectl stop. 2) How do you set up a virtual host in Apache? <VirtualHost www.amitmaheshwari.in> ServerAdmin admin@amitmaheshwari.in DocumentRoot /home/apache/share/htdocs/hostedsites ServerName www.amitmaheshwari.in ErrorLog /home/apache/logs/error/hostedsites/error_log TransferLog /home/apache/logs/access/hostedsites/access_log </VirtualHost> 3) What is mod_vhost_alias?  Full Article…

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SSH Login Without Password

1. Create an SSH Key Use the ssh-keygen command to create an SSH key.  Accept all the defaults by pressing ENTER at every prompt.  You’ll want to leave the passphrase empty. linuxsvr01$ ssh-keygen Generating public/private rsa key pair. Enter file in which to save the key (/home/user/.ssh/id_rsa): Enter passphrase (empty for no passphrase): Enter same  Full Article…

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OSI model

  In order to help you understand the OSI Model, I am going to briefly describe how each layer functions in a Building Automation System framework: Physical Layer- This is the media you use to communicate (RS-485/Ethernet ect). Data Link Layer– This is the subnet communication, or for example, the communication of MS/TP on a  Full Article…

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Find where inodes are being used

So I received a warning from our monitoring system on one of our boxes that the number of free inodes on a filesystem was getting low. df -i output shows this: Filesystem Inodes IUsed IFree IUse% Mounted on /dev/xvda1 524288 422613 101675 81% / As you can see, the root partition has 81% of its  Full Article…

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Understanding TCP/IP Subnets

A TCP/IP subnet is a segment of a network where all of the computers on that segment can communicate with each other without having to go through a router.  The computers on the subnet will have IP addresses that are within a given range of addresses, and those addresses will all have the same network  Full Article…

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bc

bc, for basic calculator   bc takes the following options from the command line: -h, –help Print the usage and exit. -l, –mathlib Define the standard math library. -w, –warn Give warnings for extensions to POSIX bc. -s, –standard Process exactly the POSIX bc language. -q, –quiet Do not print the normal GNU bc welcome.  Full Article…

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Configure TCP/IP from the Command Prompt – Windows

In order to configure TCP/IP settings such as the IP address, Subnet Mask, Default Gateway, DNS and WINS addresses and many other options you can use Netsh.exe. Netsh.exe is a command-line scripting utility that allows you to, either locally or remotely, display or modify the network configuration of a computer that is currently running. Netsh.exe  Full Article…

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Configure Static IP Address in CentOS

The following steps will show configuration of static IP address in CentOS machine. Files needed for network configuration are under /etc/sysconfig/network-scripts. So open the file with editor like nano or vi. Here I will use nano editor. After you start your server running CentOS enter root user credentials and get in. Type the command, #  Full Article…

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DATACENTER TIER CLASSIFICATIONS

The overall design of a datacenter is often classified as belonging to “Tier I–IV” Tier I datacenters have a single path for power and cooling distribution, without redundant components. Tier II adds redundant components to this design (N + 1), improving availability. Tier III datacenters have multiple power and cooling distribution paths but only one  Full Article…

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You’ve got nothing but a laptop that’s been assigned a DHCP address and no other special privileges. Explain the steps you would take to discover the network topology from there

Now, this is a loaded question. Practically speaking, there is a limited amount of network that can be discovered if it’s even vaguely secure, but an engineer that’s been around the block will come up with hopefully several of the following answers. Running a ping sweep against a range of addresses. Running a packet analyzer  Full Article…

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Kernel Using PXE Boot

So, here’s the plan: Set up a PXE environment. Find the minimal kernel config that exhibits the issue. Create a custom initrd containing all the tools needed to detect whether an issue is there. Create a script that can be reliably used by git bisect to make it all run automatically. PXE PXE is a  Full Article…

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Fiber Optic Cable Types

Fiber Optic Cable Types   Simplex Cable Single strand of fiber surrounded by a 900 um buffer then a layer of Kevlar and finally the outer jacket.   Available in 2mm or 3mm Plenum or Riser Jacket.   Plenum is stronger and made to chare in fire versus riser is made to melt in fire.  Full Article…

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Fiber Optic Tutorial – Commonly Used Fiber Connectors

  What are Fiber Optic Cables? Fiber optic cables consist of a glass core and cladding, buffer coating, Kevlar strength members and a protective outer jacket. Fiber optic cables use light pulses as opposed to electrical signals to send information. How are Fiber Optic Cables used? Fiber optic cables can be plugged into communications equipment  Full Article…

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Tehnical Interview

What are all the components in a PC or Server? PC: chassi, system board, psu, cpu, ram, hdd, fans, cables, graphics card, dvd, monitor, keyboard/mouse Server: same with deduction of a extra graphics card (is one on the system board), and addition of hdd controller, possibly backplane, no cd/dvd, extra nic, double cpu, ram, psu,  Full Article…

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