How to set up Zimbra mail server on CentOS

In this tutorial, we will examine the process of installing Zimbra mail server in CentOS Linux environment. Zimbra is my personal favorite when it comes to open-source mail servers as it comes with a number of useful features such as built-in calendar support, email filtering rules, a modern interface for both users and admins, spam […]
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How to migrate Cacti to a new server

Cacti is a popular network graphing tool widely used by many service providers. For those of you who have been using Cacti to visualize the performance of various elements of your network, it is sometimes necessary to migrate Cacti and all its graph datasets from one server to another. Why? The current server may be […]
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How to enable incremental file sync for many users on Linux

Suppose you as a software developer has set up daily builds of your software for testing purposes. Every day you make a new build, users have to re-download the updated build to evaluate it. In this case you may want to enable differential downloads, so that users can download only difference between two builds, thereby […]
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How to connect your LAN to Amazon Virtual Private Cloud

If you have a lot of your services hosted in the Amazon AWS public cloud, and are looking for ways to access your leased AWS resources in a secure way, this article is for you. Initially you started out accessing Amazon AWS over the public Internet. Over time, you have migrated more and more services […]
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How to monitor OpenFlow messages with packet sniffer

As a key enabler for software-defined networking (SDN), OpenFlow was initially introduced in the academia as a way to enable innovation on production networks which had traditionally been built with closed and proprietary networking hardware. OpenFlow offloads the high-level routing/forwarding decisions (control plane) from networking devices such as switches, and moves the control plane on […]
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What are good web server benchmarking tools for Linux

As far as web server performance is concerned, there are many different factors at play, e.g., front-end application design, network latency/bandwidth, web server configuration, server-side in-memory cache, raw hardware capability, server load of shared hosting, etc. To compare and optimize web server performance under such a wide array of factors, we often perform load test […]
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How to disable Network Manager on Linux

Network Manager is a feature-rich network configuration service which is used by default in most Linux desktop environments nowadays. It provides automatic configuration of (wired/wireless) network interfaces, as well as VPN, mobile broadband and even Bluetooth connections. Network Manager is smart enough to automatically switch to the best (or the most recent) connection network, and […]
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How to block network traffic by country on Linux

As a system admin who maintains production Linux servers, there are circumstances where you need to selectively block or allow network traffic based on geographic locations. For example, you are experiencing denial-of-service attacks mostly originating from IP addresses registered with a particular country. In other cases, you want to block SSH logins from unknown foreign […]
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How to use Mutt email client with encrypted passwords

Mutt is an open-source email client written for Linux/UNIX terminal environment. Together with Alpine, Mutt has the most devoted followers among Linux command-line enthusiasts, and for good reasons. Think of anything you expect from an email client, and Mutt has it: multi-protocol support (e.g., POP3, IMAP and SMTP), S/MIME and PGP/GPG integration, threaded conversation, color […]
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How to send email notifications using Gmail SMTP server on Linux

Suppose you want to configure a Linux app to send out email messages from your server or desktop. The email messages can be part of email newsletters, status updates (e.g., Cachet), monitoring alerts (e.g., Monit), disk events (e.g., RAID mdadm), and so on. While you can set up your own outgoing mail server to deliver […]
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