When you connect an external hard drive with LVM volumes to a RHEL, CentOS, or Rocky Linux system, the logical volumes don’t automatically appear in /dev. Unlike some distributions that handle this automatically, you need to manually activate them using vgchange. Activating LVM Volumes First, plug in your external drive. Then activate all logical volumes…
When you run a curl GET request with spaces in the query string, the shell interprets the space as a separator and truncates the URL: curl “http://example.com/send?msg=hello world” The space causes the shell to treat world as a separate argument, so only hello gets sent. You need to properly URL-encode the space (and other special…
When you compile or run screen on a remote host where you lack root privileges, you’ll often hit this error: Cannot make directory ‘/var/run/screen’: Permission denied This happens because screen needs a socket directory to manage sessions, and /var/run/screen is owned by root. If screen isn’t already installed system-wide, you can’t create this directory without…
When sending POST requests through a Squid proxy with curl, you may encounter a proxy error that blocks the request, even though the same request works fine with GET. The issue typically appears as: ERROR The requested URL could not be retrieved The root cause is the Expect: 100-continue header that curl automatically adds to…
Lightning cables are everywhere, but not all of them work reliably with iPhones. If you’ve bought a cheap third-party cable that stopped working or wouldn’t charge properly, you’ve hit the core problem: counterfeit and non-certified cables are rampant online and in retail stores. The safest approach is buying directly from Apple, but that’s not always…
Many legacy projects require specific GCC versions that differ from your system default. Ubuntu makes this straightforward through the package manager and the update-alternatives system. Check available GCC versions First, see what versions are available in your distribution’s repositories: apt-cache search ^gcc- | grep -E ‘^\s*gcc-[0-9]’ For Ubuntu 20.04 and later, you’ll typically find GCC…
When you see output like this from hdfs dfsadmin -report, you need to understand what each metric means and how to respond: Under replicated blocks: 139016 Blocks with corrupt replicas: 9 Missing blocks: 0 Understanding block states in HDFS is essential for cluster health. The distinction between these categories determines how urgent your response needs…
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:…
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…
If you’re running AdSense responsive ads on a content area narrower than full viewport width, you’ve probably noticed the ads default to horizontal (leaderboard) formats instead of the vertical rectangle ads that typically perform better. You can control which ad sizes appear by modifying the ad format parameter. The Problem with Auto Format When you…
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…
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 “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…
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…
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…
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…
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…
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…
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…