Force Linux to reboot 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…
Diagnosing High TCP Retransmission Rates in Virtual Machines 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…
Installing Scala from the official distribution 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…
Install Java Scala runs on the JVM, so you need Java installed first. Install the default JDK with: sudo dnf install java-latest-openjdk java-latest-openjdk-devel On Fedora, this installs OpenJDK to /usr/lib/jvm/java-*-openjdk-* and symlinks it as /usr/lib/jvm/java. Verify the installation: java -version javac -version Install Scala Scala is available in the Fedora repository. Install it with: sudo…
Excluding repositories in dnf/yum You’ll sometimes need to exclude specific repositories from package operations—typically when multiple repos provide the same package, mirror connectivity is unreliable, or you want to force installation from a trusted source. The –disablerepo flag lets you skip repos on a per-command basis. Basic syntax dnf –disablerepo=repoid1 –disablerepo=repoid2 install package-name Add –disablerepo…
Getting Assembly Code from OCamlopt To generate native assembly code (x86-64 asm, ARM64, etc.) from OCaml’s native compiler, use the -S flag along with other optimization-related options: ocamlopt -S -inline 20 -nodynlink not.ml -o not.opt This produces a .s file containing the generated assembly. The flags break down as: -S — Stop after assembly generation…
Customizing Question2Answer RSS feeds to show excerpts Question2Answer’s RSS feed configuration includes a toggle for “Include full text in feeds” but offers no built-in option to display excerpts instead of full content. If you need excerpt functionality, you’ll need to modify the feed generation code. This approach works with Question2Answer 1.5.4+. The method involves creating…
MySQL Table Corruption: Detection and Repair A MySQL table marked as crashed typically occurs after unclean shutdowns, power failures, or server crashes. Error 145 indicates the table structure is corrupted and needs repair before queries can proceed. Checking Table Status Before attempting repair, check the table status: CHECK TABLE mybb_sessions; This returns detailed information about…
Understanding the Content-Type Issue When you pipe a plain text file to mailx, it analyzes the content to determine the MIME type. If it detects non-standard characters (anything other than newlines and horizontal tabs), it defaults to application/octet-stream and base64-encodes the message. Most email clients then treat this as an attachment rather than inline content….
Storage of routing table entries Linux routing tables exist in kernel memory during runtime. To persist routes across reboots, you need to store them on disk and have them reloaded during system startup. The mechanism varies depending on your network management setup. systemd-networkd and netplan (modern systems) On contemporary distributions using systemd-networkd or netplan, define…
Saving Word Documents as PDF Converting Word documents to PDF is a fundamental task in most workflows. Modern versions of Office have native PDF export built in, but understanding your options and potential gotchas will save you time. Native PDF Export (Modern Office) If you’re using Office 2010 or later, PDF export is built into…
Using OCaml as a Scripting Language You can run OCaml scripts directly from the command line with a shebang, similar to bash or Python. This requires making the file executable and using the proper interpreter directive. Basic Script Setup Create a file with a .ml extension and add a shebang at the top: #!/usr/bin/env ocaml…
Listing Remote Branches in Git Local branches List all branches on your local repository: git branch This shows only branches that exist locally on your machine. Remote branches To list all branches on the remote server, use the -r flag: git branch -r This displays remote-tracking branches — local references to branches that exist on…
iTunes Backup Locations iTunes backups are stored in device-specific directories. The location depends on your operating system: macOS: ~/Library/Application Support/MobileSync/Backup/ Windows: %APPDATA%\Apple Computer\MobileSync\Backup\ On Windows, the easiest way to navigate there is to press Win + R, type %appdata% and hit Enter, then navigate to Apple Computer\MobileSync\Backup\. Understanding iTunes Backup Files iTunes stores backups as…
Printing Web Pages Effectively Copying webpage content directly into a document often produces poor formatting, missing images, or broken layouts. Here are several practical approaches to get clean, readable output. Browser Print Dialog (Native) Most modern browsers have built-in print functionality that’s worth trying first: Open the page in your browser Press Ctrl+P (Linux/Windows) or…
Booting Fedora with an older kernel in GRUB2 Modern Fedora systems keep multiple kernel versions available, but older kernels are tucked in a submenu rather than appearing as top-level GRUB2 entries. This requires a slightly different approach when setting them as your default boot option. Understanding the GRUB2 submenu structure When you run: grep menuentry…
Loading source files into the OCaml toplevel To load and execute code from a source file in the OCaml interactive toplevel, use the #use directive: #use “file-name”;; This reads, compiles, and executes OCaml phrases from the specified file as if you’d typed them directly into the toplevel. Execution stops at the first error encountered. Common…
Package Management Tools for OCaml Managing OCaml packages effectively depends on your workflow and environment. The current standard is OPAM (OCaml Package Manager), which handles dependency resolution, version switching, and sandboxed environments. OPAM: The Standard Choice OPAM is the de facto package manager for OCaml and is maintained by the OCaml community. Install it using…
Calling C Functions from OCaml OCaml provides robust FFI (Foreign Function Interface) capabilities for calling C code. This is essential when you need to use existing C libraries or write performance-critical sections in C. Using the Unix Module The simplest approach for Unix/Linux system calls is the built-in Unix module, which wraps common POSIX functions…
Setting Chrome proxy settings from the command line on Linux Chrome supports proxy configuration via command-line flags, which is useful for scripting, automation, or testing without touching the GUI settings. This works across all major Linux distributions. Basic proxy configuration Use the –proxy-server flag when launching Chrome: google-chrome –proxy-server=”socks://localhost:8080″ Proxy scheme formats The proxy specification…