System Administrator | HA Proxy setup and configuration

When an application becomes popular, it sends an increased number of requests to the
application server. A single application server may not be able to handle the entire load
alone. We can always scale up the underlying hardware, that is, add more memory and
more powerful CUPs to increase the server capacity; but these improvements do not
always scale linearly. To solve this problem, multiple replicas of the application server
are created and the load is distributed among these replicas. Load balancing can be
implemented at OSI Layer 4, that is, at TCP or UDP protocol levels, or at Layer 7, that
is, application level with HTTP, SMTP, and DNS protocols.

In this recipe, we will install a popular load balancing or load distributing service,
HAProxy. HAProxy receives all the requests from clients and directs them to the actual
application server for processing. Application server directly returns the final results to
the client. We will be setting HAProxy to load balance TCP connections.

haproxy

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Linux System Administrator | Squid Proxy Server- Installation & Configuration

The term proxy is generally combined with two different terms: one is forward proxy and the other is reverse proxy.

When we say proxy, it generally refers to forward proxy. A forward proxy acts as a
gateway between a client’s browser and the Internet, requesting the content on behalf of
the client. This protects intranet clients by exposing the proxy as the only requester. A
proxy can also be used as a filtering agent, imposing organizational policies. As all
Internet requests go through the proxy server, the proxy can cache the response and
return cached content when a similar request is found, thus saving bandwidth and time.

A reverse proxy is the exact opposite of a forward proxy. It protects internal servers
from the outside world. A reverse proxy accepts requests from external clients and
routes them to servers behind the proxy. External clients can see a single entity serving
requests, but internally, it can be multiple servers working behind the proxy and sharing
the load.

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DNS in Linux for System Administrator | Part 2

In today’s article we will show you how to install, configure and administer BIND 9 as a private DNS server.If you are interested in understanding the basic working of a DNS query and how a server responds to that query, or in other words, if you want to understand how a computer uses a DNS server to resolve domain names to IP addresses, then i will recommend reading previous blog.

Based on working method types of DNS are there, few are mentioned below

  1. Primary / Master DNS
  2. Slave DNS
  3. Forwarding DNS
  4. Caching DNS
  5. Authoritative-Only DNS

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DNS in Linux for System Administrator

Why is DNS important?

DNS is like a phone book for the Internet. If you know a person’s name but don’t know their telephone number, you can simply look it up in a phone book. DNS provides this same service to the Internet.

When you visit http://facebook.com in a browser, your computer uses DNS to retrieve the website’s IP address of 31.13.69.228. Without DNS, you would only be able to visit our website (or any website) by visiting its IP address directly, such as http://31.13.69.228.

rupin@L687:~$ ping facebook.com
PING facebook.com (31.13.69.228) 56(84) bytes of data.
64 bytes from edge-star-mini-shv-01-iad3.facebook.com (31.13.69.228): icmp_seq=1 ttl=42 time=347 ms

When a linux computer looks for another computer IP it looks for the information in two files : /etc/hosts and /etc/resolv.conf. The order in which the files are consulted is configured on /etc/nsswitch.conf:

$ cat /etc/nsswitch.conf
hosts: files,dns

Search first on files (/etc/hosts) and then on dns (/etc/resolv.conf).

/etc/hosts:
This file is a simple database that relates a numeric IP with a hostname. It can be edited as a normal file with ‘vi’ command in order to add more information.

# cat /etc/hosts
 127.0.0.1 localhost.localdomain localhost
 192.168.1.1 rupin.server.com server

The first line maps the 127.0.0.1 IP to the hostnames localhost, short hostname, and localhost.localdomain, FQHN hostname. The second line maps the 192.168.1.1 IP to server and rupin.server.com hostname.

/etc/resolv.conf:
In order to configure a linux computer as a DNS client the file /etc/resolv.conf must be used.

# cat /etc/resolv.conf 
 search info.net
 nameserver 192.168.1.1 

In this case all DNS queries launched from the computer will be addressed to the nameserver on 192.168.1.1. If a short hostname is provided it will be complemented automatically with ‘info.net’ domain.

Note: By default if a DNS query is done and can be answered from /etc/hosts the nameserver configured on /etc/resolv.conf is not consulted. Only the information obtained from /etc/hosts is taken as valid.

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WordPress-installation-using-bash-script-with-nginx-web-server

What is WordPress?

WordPress is a free and open-source content management system (CMS) based on PHP and MySQL.[5] WordPress is installed on a web server that is either part of an Internet hosting service or a network host in its own right. The first case may be a service like WordPress.com, for example, and the second case could be a computer running the software package WordPress.org.[6] A local computer may be used for single-user testing and learning purposes.

WordPress has a web template system using a template processor. Its architecture is a front controller, routing all requests for non-static URIs to a single PHP file which parses the URI and identifies the target page. Once downloaded, WordPress installation files have a size of about 20 MB.

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setup free DDns for your home pc using no-ip and router setting for no-ip

———————-Theory——————

Dynamic DNS (DDNS or DynDNS) is a method of automatically updating a name server in the Domain Name System (DNS), often in real time, with the active DDNS configuration of its configured hostnames, addresses or other information.

Your IP address is just like your phone number, but it is your computers personal phone number on the internet. It is used by your Internet Service Providers to connect your computer to the Internet. Your computer doesn’t have the same number every day, it has a dynamic IP address, meaning it changes. It could change once a month, once a week, or even a few times a day, but it does change. Dynamic IP addresses are very common since they are cost effective for ISPs.

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Setup local Environment using vagrant

Introduction:-

Vagrant is an open source tool for building a complete virtual development environment. Very often, a test environment is required for testing the latest release and new tools. Also, it reduces the time spent in re-building your OS. By default, vagrant uses virtualbox for managing the Virtualization. Vagrant acts as the central configuration for managing/deploying multiple reproducible virtual environments with the same configuration.

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