When troubleshooting wireless performance, you need to know both the negotiated link speed and actual throughput. ethtool won’t help here — it’s for wired interfaces. For wireless adapters, you’ll need different tools depending on what information you’re after. Using iwconfig for link speed The iwconfig command shows the currently negotiated link rate between your adapter…
When you need to verify the current link speed of a network interface — whether it’s running at 10Mbps, 100Mbps, 1Gbps, or higher — ethtool is the standard tool for the job. Using ethtool to check interface speed The basic command is straightforward: ethtool eth0 Replace eth0 with your actual interface name. Here’s sample output:…
SSH performs reverse DNS lookups on connecting clients by default. If your DNS infrastructure is slow or misconfigured, this can add several seconds to every login attempt. Disabling this lookup is a straightforward performance optimization, especially in cloud environments where internal IPs often lack valid PTR records. Disable the UseDNS Setting Edit /etc/ssh/sshd_config: sudo nano…
The glibc implementation of strstr() is a practical case study in algorithm selection. Rather than a naive O(n*m) search, it uses the Two-Way string matching algorithm for better performance on both short and long needles. The Basic Approach The strstr() function in glibc (found in string/strstr.c) starts with a quick check: it scans forward comparing…
After installing Xen on AMD systems, you may see continuous “powernow-k8 transition frequency failed” messages on the console. This happens because the powernow_k8 driver (AMD CPU power management) is incompatible with Xen’s CPU handling and tries to manage frequencies that Xen controls. Quick Fix The simplest solution is to unload the conflicting module: sudo rmmod…
The “rtnetlink answers: File exists” error typically occurs when restarting network interfaces on Linux, particularly after switching from DHCP to static IP configuration. This happens because the kernel’s routing table has stale entries that conflict with the new configuration you’re trying to apply. Why This Error Occurs When you change network settings and restart the…
Gmail’s SMTP service is widely used for automated mail sending, but it enforces strict rate limits to prevent abuse. Understanding these limits is critical when building mail applications or batch sending systems. Official Rate Limits Google’s official documentation on sending limits is at https://support.google.com/mail/answer/22839. The key constraints are: 500 recipients per day maximum: Sending to…
If you’re stuck at the Ubuntu login screen with errors like “Could not write bytes: Broken Pipe” or “Check Battery State,” the display manager is likely corrupted or misconfigured. This typically indicates a problem with LightDM, Ubuntu’s default display manager since 12.04. Understanding the Problem LightDM (the lightweight X display manager) manages your login session…
When processing delimited data in Bash, you often need to drop the last N fields from each line without knowing the total field count. The naive cut -d’.’ -f1 approach fails immediately when field counts vary. Given input like: systemd.3.gz systemd.mount.3.gz systemd.mount.f.3.gz You want to remove the last 2 fields (.3.gz) to get: systemd systemd.mount…
Vim is fast by default, but plugins can introduce noticeable lag during startup or while editing. Finding the culprit requires systematic profiling of both startup time and runtime behavior. Profile Vim startup time The quickest way to identify slow plugins is to measure how long Vim takes to initialize: vim –startuptime profile.log This creates a…
Xen hypervisor command line options are kernel parameters passed during boot that control how the Xen hypervisor initializes and operates. These affect CPU scheduling, memory management, virtualization features, debugging, and more. Finding Xen Command Line Options The official documentation is the authoritative source for Xen hypervisor parameters. For your installed Xen version, consult: Official Xen…
YouCompleteMe’s installation script fails on Fedora with a CMake error about missing PYTHON_LIBRARIES and PYTHON_INCLUDE_DIRS, even when Python is already installed. The error looks like this: CMake Error at /usr/share/cmake/Modules/FindPythonLibs.cmake:201 Could NOT find PythonLibs (missing: PYTHON_LIBRARIES PYTHON_INCLUDE_DIRS) The issue is that you have the Python runtime libraries installed but not the development headers needed for…
Finding and sorting files by modification time across directories is a common task for log rotation, cleanup scripts, and audit purposes. Here are the most practical approaches. Using find with printf (simplest method) The find command with -printf is the fastest and most portable approach: find . -type f -printf ‘%T@ %p\n’ | sort -rn…
EPS (Encapsulated PostScript) files are vector graphics commonly used in academic papers, technical documentation, and professional publishing. If you need to modify an EPS file, you have several options depending on your workflow and the complexity of edits required. Using Inkscape Inkscape is the most straightforward tool for editing EPS files on Linux. It’s a…
Double-blind peer review is a standard evaluation process used by many academic conferences and journals, particularly in computer science. Understanding how it works is essential before submitting your paper. What is Double-Blind Review? Double-blind review means that reviewers and authors remain anonymous to each other throughout the evaluation process. Neither party knows the identity of…
When you change thumbnail dimensions in WordPress, existing images won’t automatically resize to match. You need to regenerate them — either through a plugin or command line. Using a Plugin The easiest approach is the Regenerate Thumbnails plugin. Install it from WordPress.org, then activate it. Once activated: Navigate to Tools → Regenerate Thumbnails Click the…
Google Custom Search Engine (now part of Programmable Search Engine) lets you offload search functionality to Google’s infrastructure. Redirecting WordPress search queries to CSE can improve search quality, especially for large sites with poor built-in search performance. How it works WordPress uses the s query parameter by default when processing searches from the search form….
When your C: drive fills up with user profile data, moving the entire user directory to another drive is a legitimate solution—but it requires careful execution and understanding of the tradeoffs involved. Why This Matters User profiles contain everything: Documents, Desktop, Downloads, AppData, and all application settings. On a full C: drive, this can easily…
When your application fails to bind to a port, you need to identify what’s already using it. This is one of the most common debugging tasks in Linux system administration. Using ss (Modern Approach) The ss command has largely replaced netstat in modern Linux distributions. It’s faster, more efficient, and provides clearer output: ss -ltnp…
VirtualBox’s scaled mode stretches the guest display to fill your host window, but it can distort the image or make it harder to work with. If you need to switch back to normal windowed mode, you have a few options. Using the Keyboard Shortcut The quickest way to exit scaled mode is with the keyboard…