How to set up Apt caching server on Ubuntu or Debian

If you often create guest VMs or containers on your Linux computer, you will go through package installation many times across different VMs/containers. In that case, your time may be better spent on something more productive than just waiting to finish installing packages. While server provisioning tools like Puppet, Chef or Ansible can automate the […]
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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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How to search multiple pdf documents for words on Linux

When it comes to searching text within a PDF document, pretty much every PDF reader supports it. However, it becomes tricky when there are more than one PDF document to search. While the official Adobe Reader offers multiple PDF search functionality (i.e., searching all PDF files in a directory), it has discontinued on Linux. None […]
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How to access Amazon Cloud Drive from the command line on Linux

In today’s online retail market dominated by cut throat competitions, one player stands in the forefront, leaving the pack far behind, and that is Amazon. Amazon has been judiciously expanding its business model to satisfy consumer appetites, and I think Amazon Prime membership lies in the center of its expanding business model. Starting out as […]
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What is good stock portfolio management software on Linux

If you are investing in the stock market, you probably understand the importance of a sound portfolio management plan. The goal of portfolio management is to come up with the best investment plan tailored for you, considering your risk tolerance, time horizon and financial goals. Given its importance, no wonder there are no shortage of […]
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How to use KVM from the command line on Debian or Ubuntu

There are different ways to manage virtual machines (VMs) running on KVM hypervisor. For example, virt-manager is a popular GUI-based front-end for VM management. However, if you would like to use KVM on a headless server, GUI-based solutions will not be ideal. In fact, you can create and manage KVM VMs purely from the command […]
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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 secure your Linux environment with Nitrokey USB smart card

With the mounting online security risks, simple one-step security no longer suffices, and people resort to multiple layers of security to thwart increasingly sophisticated attacks on their digital assets and online privacy. An advanced form of security defense often employed in financial sectors and other corporate environments is hardware-based protection, where a tamper-proof physical security […]
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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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