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HOW TO SETUP YOUR OWN MAIL SERVER WITH ANTI-SPAM CONFIGURATION

Introduction

This tutorial will teach you how to set up your own robust email server. We are focusing on a small personal server with up to a few email accounts. After following this guide, you will have a fully functional mail server and you can connect with your favourite client to access, read and send emails. The Anti-Spam configuration will drop unwanted messages.

This tutorial will use yourdomain.com as domain name and mail.yourdomain.com as hostname for our mail server. The desired email address will be  This e-mail address is being protected from spambots. You need JavaScript enabled to view it . We assume that our server has the IP address 1.2.3.4.

Software and technologies used

  • Postfix v2.9.6 as SMTP server
  • Dovecot v2.0.19 as IMAP server
  • We will use Unix user accounts and tunnel the SASL authentication through TLS
  • Postgrey v1.34 – to reject spam from the beginning
    (more about postgrey)
  • SPF (Sender Policy Framework) validating to reduce spam
    (more aboutSPF)
  • SPF DNS entry to prevent spoofing
  • DKIM (Domain Keys Identified Mail) to sign our email messages
    (moreabout DKIM)

Read on over here...

 

Install Ajenti Control Panel on CentOS, RedHat and Fedora

Ajenti is a web based control panel for managing systems (like: Webmin, cPanel). It has a very beautiful and user-friendly interface. For personal use Ajenti is freely available for under AGPLv3. For commercial use you have to pay for a small amount regularly.

Below article article will help you to install Ajenti control panel on CentOS, Redhat and Fedora systems.

http://tecadmin.net/install-ajenti-control-panel-on-centos-redhat-fedora/

 

Web Application Development in Linux Environment

Web Application Development

This article is presented by Vijay Web Solutions India Pvt. Ltd., a complete mobile and web application development company in India. The article represents the technologies used for developing web applications focused, comparing open source alternative to proprietary supported in Linux, also commenting on performance and development time.

Comparing Alternative Distribution

Currently there is a wave of development / export of most applications for use on the web. It should be emphasized that one should be careful when doing this as it should analyze the real need of it, so the development of web applications is more complex than the development of executable applications.

Solutions such as application delivery are needed in companies that have branches / points distributed over a considerable distance geographically. Citrix Metaframe is one of the tools that is installed on a Windows server with great performance hardware, allows publishing of any program installed on it. It provides user friendly interface to define which users can access each application published and how many instances of this application can run simultaneously according to the number of licenses. It is a great solution because it works with complex software applications made by going to the DOS platform. Greatest obstacle in such a solution is its cost, it can turn into more than $ 20,000.00 just for this tool with a considerable server hardware.

An alternative would be to develop web applications for use in the browser and distributed via a web server. I have always wondered about what would use more network traffic. Both forms are processed on the server, both using a metaframe as using a web application. But think about how it would be to transfer the image generated by the client instance on the server that is to be transferred to the client metaframe, if it would generate more traffic than sending an HTML document.

Greatest attractive to use the second option is you can use the Unix platform and our old known as Apache web server. For such applications there are several free to use database management systems like PostgreSQL, Firebird or even the most popular MySQL, which is widely used for its integration with PHP. Nor would there be problems in integrating an application that was being published by a Linux server with Apache to access databases on a Windows server, for example.

Database

Applications always require Relational Database Management Systems (RDBMS). Currently, there are several alternatives available in the market, being always hottest, the Oracle, currently at version 12c (c stands for cloud) and Microsoft SQL Server at version 2014. These solutions are great, however cost a bit outside the context of many companies on the rise. Alternatively, the DBMSs appeared attractive for situations like this, because despite being free to use, features stable operation and very good consistency.

There is availability of versions available for various distributions of Linux. Among them we can mention the PostgreSQL, which has characteristics and features that do not want to leave it on business. Firebird which is the freeware version of our renowned Interbase, having the same characteristics and is compatible with the same. But, surely you could not miss the MySQL which despite being the least robust of the three above options is the most used. A lot of web application development companies developing commercial applications working with PostgreSQL, to be the most robust among them and implement a best aspects safety. The Firebird still leaves a bit to be desired in this regard. The adoption of tools like these in projects reduces the cost of deploying the systems in customers. This facilitates their financial customer acceptance which might not be achieved only with the use of these free alternatives.

Technologies for Development

For the development of applications, use some CGI tool able to interpret the scripts on the server and return a default output to the user (HTML), to interact and post this information to be processed on the server, etc... There are several tools available on the market, thus as in the database have the paid and free to use. There are still very large number of servers using ASP which is Microsoft proprietary, which can only be installed on a server running Windows.

In return, we have solutions that are platform as JSP (Java Server Pages), PHP, and ColdFusion, which despite to be paid, and support installation on various distributions of Linux. Initially, in response to the use of ASP, PHP, which has spread a lot and gained a lot of fans is the clear language for programming that supports development with the paradigm of object orientation. The reason both has widespread, because there are several packages and documentation available on the Internet for both of these technologies.

Another tool that has been growing very equaling or even surpassing is JSP, because being originated from Sun's Java technology, it presents as a very consistent solution due to the great support that provides the Java language and how big the opponent group .NET from Microsoft. Also it supports the deployment on a Linux server. A proprietary solution that many are unaware that also supports Linux is Adobe ColdFusion currently at version 11. We will briefly discuss about it in the paragraphs below.

It offers the possibility to run on a Linux server with Apache and consult a base in a MS SQL Server on a Windows server. It is a simple and clear language, with advantages and disadvantages over the others. How big advantage is the ability to rapidly develop, because the language has different tags, such as CFINPUTs, which besides having the same attributes of INPUTs defined in HTML, allow the tag itself set the field validation on the client, messages, etc... without the need to write code in Javascript for this, as it would be in the languages mentioned above.

ColdFusion automatically generates these codes. Allows integration with Java technology since their codes are compiled and these generated classes in Java are used to send the output to the user. Disadvantages are that the cost for its implementation is necessary to acquire a license to power up Install the server and the CF developer community is very small in relation to the other. For example, to generate a PDF document that in the case of PHP and JSP must be native or using packages and libraries in CF only with proprietary solutions support. Notes on a case study that although it consume a considerable amount of RAM memory and other resources, it has a good performance microprocessor Pentium IV 2.4 MHz, 1GB of RAM and a 800MHz local bus without the need for a dual server.

All this with the Apache web server with SSL support. A detail that is worth noting that in this case study that I have seen, opening a series of doors services the CF, the more interesting it would be to place a firewall even before avoid direct external access.

Conclusion:

With this article, we hope to have contributed to the analysis of its structure helping to choose the path you want to follow. Proprietary solutions can be integrated into the Linux platform bringing benefits and reducing the cost. If the company can invest in a solution based on CF aimed at the rapid development of the projects, this can be achieved in the Linux environment.

 

Install EPEL Repo on a CentOS and RHEL 7.x Server

A larger number of packages can be installed from Fedora EPEL repo on a CentOS and Red Hat Enterprise Linux (RHEL) version 7.x. This quick tutorial explains how to enable Fedora EPEL repo on a Red Hat Enterprise Linux server version 7.x or CentOS Linux server version 7.x.

Read more: Install EPEL Repo on a CentOS and RHEL 7.x

 

CentOS and RHEL 7: Install Linux, Apache, MariaDB, PHP (LAMP) Stack

I am new Red Hat Enterprise Linux version 7 user/sysadmin/developer. This version made the big number change for RHEL 7/CentOS 7. How can I install LAMP (Linux, Apache, MariaDB, PHP) stack on a RHEL version 7 or CentOS Linux version 7 using CLI or over ssh based session?

CentOS and RHEL 7: Install Linux, Apache, MariaDB, PHP (LAMP) Stack

 

How to set up KVM Virtualization in RHEL/CentOS 6

Hi Linux fans, I have been using KVM virtualization a lot recently for learning and as a lab set up to try out all my new stuff. I originally started writing articles for KVM in Ubuntu in my Jungle Geek blog. One of my readers wanted to try that out on a CentOS operating system. So I decided to write an article for KVM on CentOS to help him out.

If you are interested in learning about how to setup KVM virtualization on RHEL/CentOS, please visit my blog and the article link is below.

 

Thanks

Venkat Nagappan

 

KVM Virtualization in Ubuntu

Hi Linux Beginners, I have been writing about KVM virtualization in my blog recently. If you are interested in learning more about KVM stuff please visit my blog Jungle Geek.

My recent articles about KVM are at

All articles in KVM category in my blog can be found at

Hope you enjoy reading my articles. Thanks for reading it.

 

Setup Hadoop 2.4 Single Node Cluster on CentOS/Redhat

Apache Hadoop 2.4.0 significant improvements over the previous stable releases. This version has many improvements in HDFS and MapReduce. This how to guide will help you to install Hadoop 2.4.0 on CentOS 6.5 System. This article doesn’t includes overall configuration of hadoop, we have only basicconfiguration required to start working with hadoop. 

Read complete article at Setup Hadoop 2.4 Single Node Cluster - TecAdmin.net

 

Open Source Cloud Banking based on ERP5 released

A version of ERP5 open source ERP dedicated to Banking and hosted on Linux based SlapOS open source cloud has been publicly released. It has been already operated for 6 years in various banks. A minimal banking core setup service costs 10 KEUR with price based on number of transactions.

 

Tips for Cloud Computing Security

    Shared software, shared resources are integral elements of Cloud Computing, which has become a rage today. It’s being used by companies looking for flexibility and scalability. But there are risks involved that you have to keep in mind while using public, private or hybrid cloud computing options. Security of your vital data is of great importance to you and it should be protected while you get the best benefits of cloud computing services. To make effective use of cloud computing and to ensure that data is transferred online securely, there are certain tips you must follow.
 

Know how your data is protected

    Data encryption and firewall security is crucial and you have to know more about these aspects when you sign up with a service provider. Public cloud SaaS solutions make secure encryption practically mandatory. Cloud computing resources should also have an inbound firewall for security reasons. You might be on a cloud but you still have to have strategies in place in case there is an external attack or hostile activity on the system. Service providers that talk about their security measures openly should be given precedence because it enables you to have your own strategies in order. 
 
Read more at YourOwnLinux
Author: Ramya Raju
 

How To Build a Cloud (cluster) Hosting Without Investing a Lot of Money

Three years ago, I had an interesting problem. It was necessary to assemble a platform to combine multiple racks of servers into a single entity for the dynamic allocation of resources between sites, written for the LAMP platform.

However, the budgets were very less so expensive solutions such as Cisco Content Switch or disk shelves with fiber optics were not affordable.

And, besides, of course, in case if one server is down – this should not affect the operation of the platform was my main concern.

In my school time, I read somewhere that “Necessity is the mother of invention”, which is fairly true.

First of all you need to share a platform into subtasks. You have to do something for the synchronization of data as a shared drive is available. In addition, it is necessary to balance the traffic and have at it some statistics. Finally, the automation of providing the necessary resources – is also quite a serious problem.

Let’s start from the beginning…

I had a choice on what to organize a platform. OpenVZ or XEN ? Each has its pluses and minuses. OpenVZ has a lower overhead, work with files and does not block devices, but cannot run anything other than Linux’ovh distributions. XEN allows you to run on Windows, but more difficult work. I’ve been using OpenVZ, as this is more suited for the task, but you can choose the one you like, there is no restriction on choice.

Then I shared the server space for the VDS, one for each core. Servers were different, and therefore I had a set from 2 to 16 and virtual ok on each server. In the “average house” turned out about 150 virtual ok on the counter.

How to synchronize the data?

The next item – this is the early establishment of VDS on demand + protection against breakage of any server. The solution was simple and beautiful.

Each VDS creates the initial image as a file on the LVM partition. This image “spreads” on all servers in the platform. As a result, we have a backup of all the projects on each server (paranoid cry of emotion), and the creation of a new VDS «on demand” has been simplified to a snapshot image and it start the VDS literally in few seconds.

Database and API

If the integrity of the files were all simple, here’s a sync base things were worse. From the beginning I tried a classic example – master-slave, and collided with a classic problem: slave lag behind master.

The next step was to Mysql-Proxy. As a sysadmin, this was very easy to set and forget, but the configuration should be updated while adding / removing new VDS. But developers have had their own opinion. In particular, the fact is that, it is easier to write a PHP class for synchronization of INSERT / UPDATE / DELETE queries than to learn Lua, without which the Mysql-Proxy is useless.

Their work produced a so-called API, which was able to find neighbors of a broadcast sync up to date and to inform the neighbors of any changes to the database.

But still worth exploring Lua and make native mode, where all requests are synchronized with their neighbors.

FreeBSD

Balancer – it can be said that it is a key aspect of the platform. If they fall to balance server, all work will have no meaning.

That is why I used the CARP to create fault-tolerant balancer, choosing FreeBSD as the OS and Nginx as a balancer.

Yes, NLB has been replaced by two weak machines with FreeBSD (marketers in a rage).

And most importantly – how it works

When starting up the platform for each site runs on a single copy and monitor to balanesere watched to ensure that the primary copy has always worked.

In addition, the balancer was installed to analyze statistics Awstats, which provided all the logs in a convenient format, and most importantly – there was a script, polling each VDS via SNMP for its load.

As we remember, I devoted each VDS on one core, so Load Average in a 1 – this is a normal load for the VDS. If LA became 2 or above – the script that creates a copy of the VDS on a random server and put this in its upstream nginx’a. And when the load on extra VDS fell less than 1 -, respectively, all removed.

Summarize

If you take the rack with servers and switches supporting the CARP protocol, to create a ESDS cloud hosting Server, will need to:

  • Explore Lua and adjust transparent synchronization across Mysql-Proxy
  • Screw the billing account for additional copies of the VDS and traffic
  • Write a web interface for managing VDS
  • The filling racks with enough amount of four zeros. Compared with the decisions of the brands, where the price of one stand is the sum of six zeros, counts worth.
 
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