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Web Development

Customizing the WordPress HTML Editor with Custom Buttons
ByQ A Mar 24, 2018Apr 13, 2026

WordPress’s Text/HTML editor can be extended with custom buttons for frequently used code snippets or shortcodes. This is useful for inserting boilerplate markup, custom shortcodes, or formatting helpers without manually typing them each time. Basic Implementation Add this code to your theme’s functions.php or a custom plugin: function add_custom_quicktags() { wp_add_inline_script( ‘quicktags’, “QTags.addButton(‘wiki_button’, ‘Wiki’, ‘[yadawiki…

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Web Development

Remove WordPress Canonical Tags from HTML Head
ByQ A Mar 24, 2018Apr 12, 2026

WordPress has included automatic canonical URL generation since version 2.9. While this is usually beneficial for SEO, certain scenarios require disabling it — for example, when forum plugins generate incorrect canonical URLs that point all threads to a single page. The Problem Canonical URLs tell search engines which version of a page is authoritative. When…

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Linux & Systems Administration

Installing noip2 on Linux: A Setup Guide
ByQ A Mar 24, 2018Apr 12, 2026

No-IP provides dynamic DNS service for systems that don’t have static IP addresses. The noip2 client daemon monitors your system’s IP and automatically updates your No-IP domain when changes occur. Here’s how to set it up properly. Prerequisites You’ll need: A No-IP account with at least one hostname configured Root or sudo access A Linux…

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Scripting & Utilities

Running Firefox Remotely Over SSH
ByQ A Mar 24, 2018Apr 13, 2026

X11 forwarding over SSH lets you run graphical applications on remote systems and display them locally. Firefox is a common use case, though it requires careful configuration to avoid crashes and permission issues. Basic Setup The simplest approach uses X11 forwarding: ssh -X remotehost The -X flag enables trusted X11 forwarding. For untrusted forwarding (more…

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Linux & Systems Administration

Installing Dropbox on Linux
ByQ A Mar 24, 2018Apr 13, 2026

Dropbox on Linux has two main approaches: the official daemon (headless) or the sync client with GUI. Which you choose depends on your use case. Official Dropbox Daemon (Recommended for Servers) The daemon is lightweight and works well on headless systems. Download and extract it: cd ~ && wget -O – “https://www.dropbox.com/download?plat=lnx.x86_64” | tar xzf…

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Testing & DevOps

Efficiently Copy Large Sparse Files with SEEK_HOLE and SEEK_DATA
ByEric Ma Mar 24, 2018Apr 12, 2026

Archiving or copying a 1TB sparse file containing only 32MB of actual data is impractical with naive approaches—you’ll waste time and I/O bandwidth copying zeros. The solution is using SEEK_HOLE and SEEK_DATA flags with lseek(), which allow tools to skip over hole regions entirely. How SEEK_HOLE and SEEK_DATA work The Linux kernel provides two additional…

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Development Best Practices

.NET Core 2.1: What’s New in 2018
ByJohnnymorgan Nov 21, 2017Apr 13, 2026

This post covers .NET Core 2.1, which released in May 2018. Some of the predicted features below didn’t materialize as described; we’ll clarify what actually landed versus what was speculated. What is .NET Core? .NET Core is Microsoft’s open-source, cross-platform runtime for building applications in C#, F#, and Visual Basic. Unlike the monolithic .NET Framework…

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Linux & Systems Administration

x86-64 Instruction Encoding: From Assembly to Machine Code
ByEric Ma Sep 9, 2017Apr 12, 2026

Before encoding instructions, you need to understand the two assembly syntaxes you’ll encounter—they differ fundamentally in operand order and addressing format. Intel syntax (Intel/AMD manuals): Operand order: destination, source Memory addressing: [base+offset] Example: add r8, [rdi+0xa] AT&T syntax (GNU toolchains on Linux): Operand order: source, destination Memory addressing: offset(%base) Example: addq 0xa(%rdi), %r8 For most…

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Systems & Architecture

HDFS NameNode Metadata Checkpointing: Resolving Sync Issues
ByEric Ma Sep 9, 2017Apr 12, 2026

The Secondary NameNode periodically merges the fsimage and edits log files to keep the edits log manageable and consolidate metadata. When this checkpointing fails, you’ll see errors like: ERROR org.apache.hadoop.hdfs.server.namenode.SecondaryNameNode: Exception in doCheckpoint java.io.IOException: Inconsistent checkpoint fields. This typically indicates a mismatch between the NameNode and Secondary NameNode metadata states, often from unclean shutdowns or…

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Systems & Architecture

QEMU/KVM Networking: TAP, virtio, and vhost Explained
ByWeiwei Jia Aug 26, 2017Apr 12, 2026

QEMU/KVM networking operates across multiple layers — TAP devices, QEMU’s packet queuing, virtio descriptors, and kernel bypass mechanisms. Understanding this stack is essential for debugging connectivity issues and tuning performance in production environments. TAP Device Fundamentals TAP (TUN/TAP) devices create a bridge between the guest and host network stack. A typical QEMU/KVM configuration looks like:…

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Web Development

HTML Entity Reference Guide
ByDavid Yang Apr 20, 2017Apr 12, 2026

HTML entities represent characters that either have special meaning in HTML or benefit from explicit encoding. You have three syntax options: Named entity: &name; (e.g., ©) Decimal numeric: &#number; (e.g., ©) Hexadecimal numeric: &#xhexcode; (e.g., ©) With UTF-8 encoding (the only sensible choice in 2026), most special characters can be typed directly. However, certain characters…

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Languages & Frameworks

HTML5 Canvas: Drawing Graphics with JavaScript
ByColin Apr 18, 2017Apr 12, 2026

The HTML5 <canvas> element lets you draw graphics programmatically using JavaScript. Unlike static images or SVG, canvas renders raster (bitmap) graphics directly to a 2D or 3D surface, making it ideal for animations, games, real-time visualizations, and interactive graphics that need frequent updates. This guide covers canvas fundamentals and practical examples for sysadmins and developers…

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Linux & Systems Administration

USB Standards in Linux: Speeds and Driver Troubleshooting
ByEric Ma Apr 9, 2017Apr 12, 2026

USB technology continues evolving with each generation delivering significant speed improvements. Linux provides comprehensive kernel support across all modern standards through dedicated drivers. USB 2.0 Speed: 480 Mbps (theoretical ~60 MB/s) Status: Legacy but still common. Nearly all systems retain USB 2.0 ports for backward compatibility. Linux support: Built-in via the ehci-hcd driver in all…

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Linux & Systems Administration

Building and Installing a Linux Kernel from Source
ByEric Ma Mar 18, 2017Apr 12, 2026

Grab a release from kernel.org. Recent stable versions (6.x and later) are recommended for production systems: wget https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.12.tar.gz tar xf linux-6.12.tar.gz cd linux-6.12/ If wget isn’t available, use curl: curl -O https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.12.tar.gz Verify the tarball Always verify the kernel’s integrity using checksums and signatures published on kernel.org. This is essential for production systems: wget https://www.kernel.org/pub/linux/kernel/v6.x/linux-6.12.tar.gz.asc…

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Linux & Systems Administration

Mastering Vim: A Practical Guide to vimtutor
ByEric Ma Dec 31, 2016Apr 12, 2026

vimtutor is the most practical way to learn Vim. It’s an interactive lesson built directly into your editor that teaches through practice rather than passive reading. You launch it from the terminal with no setup required, and you get immediate feedback on every command you type. Running vimtutor From any terminal: vimtutor This opens an…

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Languages & Frameworks

Building Java CLI Applications with Spring Shell 3.x
ByJohnnymorgan Dec 23, 2016Apr 12, 2026

Spring Shell is a framework for building command-line interfaces (CLIs) in Java applications. It provides structured command definition, argument parsing, tab completion, and history management—all integrated with the Spring ecosystem. Requirements and Setup Spring Shell 3.2+ requires Java 17+ and Spring Boot 3.2+. If you’re still on older versions, Spring Shell 2.x supports Java 8…

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Linux & Systems Administration

Reducing QEMU/KVM Lock Contention with IOThreads and Dataplane
ByWeiwei Jia Dec 18, 2016Apr 12, 2026

QEMU/KVM uses global locks to synchronize threads, which is necessary for correctness but causes performance problems at scale. When multiple I/O requests and vCPU threads contend for the same lock, you get lock contention that manifests as scheduling jitter, reduced system scalability, and degraded I/O performance. IOThreads (the modern implementation of dataplane) address this by…

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Linux & Systems Administration

Measuring CFS Scheduler Timeslices in Linux
ByWeiwei Jia Dec 5, 2016Apr 12, 2026

CFS (Completely Fair Scheduling) is the default process scheduler in modern Linux kernels. Understanding actual timeslice allocation—how long a process runs before being context-switched out—is essential for performance debugging, verifying fairness assumptions, and identifying scheduling anomalies. The challenge is that /proc interfaces and ps commands show scheduling policy but not the actual on-CPU duration per…

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Linux & Systems Administration

How the CFS Scheduler Controls Process Timeslices and Preemption
ByWeiwei Jia Dec 1, 2016Apr 12, 2026

The Completely Fair Scheduler (CFS) is the default process scheduler in Linux kernels since 2.6.23. It allocates CPU time proportionally based on process priority, but the actual timeslices and preemption behavior depend on three key tunable parameters: sched_latency_ns, sched_min_granularity_ns, and sched_wakeup_granularity_ns. Understanding how these work together is essential for tuning scheduler behavior on production systems….

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Linux & Systems Administration

How Linux Kernel Migration Threads Work
ByWeiwei Jia Nov 19, 2016Apr 12, 2026

In computer systems, resources must be balanced across available hardware to maximize performance. The Linux kernel runs migration threads as per-CPU daemons to handle this work. These threads manage task migration between CPUs, CPU hotplug operations, and stop-machine synchronization. You can observe migration threads on any modern system: $ ps aux | grep migration root…

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