Vim’s regex engine is powerful but requires understanding its syntax rules, which differ significantly from standard POSIX extended regex. Whether you’re doing basic substitutions or complex text transformations, knowing how Vim handles regex patterns will save you hours of frustration. Vim Regex Basics Vim supports multiple regex engines, controlled by the magic setting. By default,…
To replace strings across one or more columns in MySQL tables, use the REPLACE() function with an UPDATE statement. This is useful when migrating domains, fixing URLs, updating API endpoints, or correcting data patterns at scale. Basic Syntax UPDATE table_name SET column_name = REPLACE(column_name, ‘old_string’, ‘new_string’) WHERE column_name LIKE ‘%old_string%’; The WHERE clause isn’t required,…
You’re seeing fatal errors because PHP has hit its default resource constraints: PHP Fatal error: Maximum execution time of 30 seconds exceeded PHP Fatal error: Allowed memory size of 268435456 bytes exhausted These limits exist to prevent runaway scripts from consuming server resources. Here’s how to increase them. Via php.ini (Global Configuration) The most reliable…
To check which storage engine a table uses, query the information_schema database: SELECT ENGINE FROM information_schema.TABLES WHERE TABLE_SCHEMA = ‘database_name’ AND TABLE_NAME = ‘table_name’; Replace database_name and table_name with your actual values. You can also use the SHOW TABLE STATUS command for a quicker view: SHOW TABLE STATUS FROM database_name WHERE Name = ‘table_name’\G The…
Install the required LAMP stack components. Fedora 41 and later use dnf instead of yum: sudo dnf install httpd php php-mysqli php-gd mariadb-server Note that php-mysql is deprecated; use php-mysqli instead for modern MySQL/MariaDB connections. Start and enable the services to run on boot: sudo systemctl start mariadb httpd sudo systemctl enable mariadb httpd Using…
Several native options now exist for annotating PDFs directly on Linux, though each has trade-offs between features and ease of use. Native Linux Tools Okular is the most straightforward choice for basic annotations. It’s lightweight, fast, and saves markups directly into the PDF: sudo apt install okular okular document.pdf Okular supports highlighting, underlining, strikethrough, freehand…
HP printers work well on Fedora when you install the right packages and drivers. Here’s what you need to do to get a USB or network-connected HP printer working reliably. Install HPLIP and Related Packages Start by installing the HP Linux Imaging and Printing (HPLIP) suite: sudo dnf install hplip hplip-gui hpijs On modern Fedora…
If gnuplot or ps2epsi fails to run or produces excessive warnings on modern Fedora systems, you’re likely hitting a fontconfig deprecation issue. The symptom is repeated warnings like: Fontconfig warning: “/etc/fonts/conf.d/50-user.conf”, line 14: reading configurations from ~/.fonts.conf is deprecated. This happens because /etc/fonts/conf.d/50-user.conf still includes a deprecated reference to ~/.fonts.conf. While the warning alone doesn’t…
If you need basic image editing without installing software or paying Photoshop’s subscription, several solid online options exist. Here’s what works well in 2026. Pixlr Pixlr remains a solid choice for straightforward editing. The web-based editor handles layers, filters, and common adjustments without much friction. Free tier covers most basic work, though premium features unlock…
Database corruption happens. Whether it’s from unexpected shutdown, filesystem errors, or hardware issues, knowing how to recover from backups is essential sysadmin knowledge. When to Use Backups vs. Native Repair Tools Before jumping to restore from backup, consider your options: Native repair tools (REPAIR TABLE, CHECK TABLE) are faster and preserve recent data Backup restoration…
The –no-print-directory flag suppresses make’s default behavior of printing messages when entering and leaving subdirectories. If you invoke make frequently with recursive calls or have a deeply nested project structure, these messages clutter your output. Rather than passing the flag on every invocation, you can set it once in your Makefile. Add this line near…
Choosing the right number of mappers and reducers directly impacts Hadoop job performance. This isn’t a set-and-forget configuration—it depends on your cluster characteristics, data size, and task complexity. Mapper Configuration The number of mappers is primarily determined by the number of HDFS blocks in your input files. Each block typically generates one map task by…
Handling Ctrl-C gracefully in a Bash script is essential when you need to perform cleanup operations, save state, or notify users before exiting. The trap builtin makes this straightforward. Basic Trap Setup The fundamental approach uses the trap command to catch the INT signal (which Ctrl-C generates): trap ctrl_c INT function ctrl_c() { echo “Ctrl-C…
When standard reboot commands fail to work, the Magic SysRq key provides a kernel-level mechanism to force a reboot or shutdown. This works even when the system is mostly unresponsive. Prerequisites Magic SysRq must be enabled at runtime or in the kernel configuration. Most modern distributions enable it by default, but you can verify and…
Spawning background processes in Bash is straightforward with the & operator, but there are several nuances depending on your use case. Basic approach The simplest method is appending & to your command: for i in $(cat ./all-hosts); do ssh “$i” “ifconfig | grep Link” & done Each & launches the process in the background and…
Facebook’s engineering team has long been vocal about their heavy reliance on MySQL to power one of the world’s largest platforms. Understanding their approach offers valuable insights for anyone managing databases at scale. Storage Engine Philosophy Facebook treats MySQL as a generic data manipulation and storage engine rather than a monolithic application database. This architectural…
Facebook operates two distinct caching systems, each designed for different access patterns and consistency requirements. Memcache serves as a lookaside cache where the intelligence resides primarily on the client side. This architecture means applications are responsible for cache invalidation, consistency checks, and determining what data to cache. Memcache is stateless and horizontally scalable, making it…
If you’re seeing elevated TCP segment retransmission counts on Xen VMs, this typically signals network congestion, packet loss, or CPU contention. Here’s how to identify the root cause and fix it. Check Your Current Retransmission Rate Start by gathering baseline metrics: ss -s Look for the retransmit counters: TCP: established 45 tw 3 alloc 48…
Chrome on iOS implements aggressive caching to improve browsing performance, but this can prevent you from seeing the latest versions of pages, stylesheets, and scripts. Unlike Safari’s convenient long-press refresh button, Chrome’s cache management is less intuitive. The Nuclear Option: Clear All Cache The most straightforward approach is clearing all cached data: Open Chrome Tap…
When your distro’s package repositories lag behind, installing Scala directly from the official release is straightforward. This approach works on any Linux system with Java already installed. Prerequisites You’ll need a JDK installed. On most systems: # Debian/Ubuntu apt install default-jdk # RHEL/Fedora/CentOS dnf install java-17-openjdk-devel # Alpine apk add openjdk17 Verify your Java installation:…