Why Use LVM for libvirt Storage By default, libvirt stores VM images as files in /var/lib/libvirt/images/. While functional, this approach limits flexibility. LVM (Logical Volume Management) provides better control over disk space, snapshots, and performance tuning. Using LVM volumes as libvirt storage pools lets you manage VM storage like block devices rather than files, giving…
Debugging Stack Overflow Exceptions in OCaml When your OCaml program crashes with Fatal error: Exception “Stack_overflow” but doesn’t tell you where the problem originated, you need to enable backtrace reporting. The process is straightforward but requires recompilation. Enable Debug Symbols and Backtraces First, recompile your program with the -g flag to include debug information: ocamlopt…
Installing sbt on Fedora Linux sbt (Scala Build Tool) isn’t available in the default Fedora repositories, though Scala itself is. Here’s how to install it properly. Using the Official Repository The most reliable approach is to add sbt’s official repository to your system. This gives you automatic updates and avoids manual RPM downloads. Create the…
Finding and Configuring Linux Timer Sources Linux systems can have multiple timer sources available, and the kernel selects one as the active clocksource. Understanding what’s available and how to view or change the current source is essential for performance tuning and troubleshooting timing-related issues. View the Current Timer Source Check which clocksource is currently in…
utop is an improved OCaml REPL with line editing, history, context-sensitive completion, and syntax highlighting. While powerful, its key bindings differ from standard GNU readline, which can be jarring if you’re used to standard shell behavior. Getting the key bindings list The simplest way to see all available bindings is to run the #utop_bindings directive…
Removing Trailing Whitespace from Files Trailing spaces and tabs at the end of lines are common annoyances in source code and configuration files. They’re invisible, waste space, and can cause issues with certain tools or version control systems. Here’s how to remove them efficiently. Using sed The most straightforward approach with sed: sed ‘s/[[:space:]]*$//’ your_file…
Converting Evolution Mail to Thunderbird and Syncing with IMAP If you have emails stuck in Evolution’s local directory structure that you want to move to an IMAP account via Thunderbird, you’ll need to convert them to a format Thunderbird can import, then push them to your mail server. Step 1: Prepare Your Evolution Mail Directory…
Xen HVM DomU Configuration Xen HVM (Hardware Virtual Machine) guests require a configuration file that defines virtual hardware, networking, and boot parameters. Here are practical examples for common scenarios. Installation Configuration Use this configuration when installing a guest OS from an ISO: name=”10.0.1.235″ vcpus=2 memory=2048 shadow_memory=8 disk=[‘file:/lhome/xen/vm-10.0.1.235/vmdisk0,xvda,w’, ‘file:/lhome/Linux-x86_64-DVD.iso,xvdc:cdrom,r’] vif=[‘bridge=xenbr0′] kernel=’/usr/lib/xen/boot/hvmloader’ builder=’hvm’ device_model=’/usr/lib64/xen/bin/qemu-dm’ vnc=1 vnclisten=”0.0.0.0″ vncpasswd=’your-secure-password’…
Data Recovery from Decommissioned Linux VMs When deprovisioning Linux VMs in public cloud environments, disk blocks may be reallocated to other customers if the provider doesn’t properly wipe storage. This is a legitimate concern for security audits, compliance validation, and understanding data exposure risks. Quick Recovery Method The most straightforward approach uses dd and strings…
Removing a Disk from an LVM Group You have an LVM physical volume (PV) you need to remove from a volume group (VG), but the data needs to be preserved and moved to other available PVs. This is a straightforward but important operation that requires careful execution. Prerequisites Before starting, verify: The VG has sufficient…
Setting up OCaml auto-indentation in Vim Vim’s default OCaml indentation is limited and doesn’t handle the language’s syntax well. You’ll want to use ocp-indent, a dedicated indentation tool built specifically for OCaml that understands the language’s scoping and structure rules. Installing ocp-indent First, install the tool via OPAM (OCaml Package Manager): opam install ocp-indent If…
Linux gives you top and htop to monitor CPU and memory by process, but network traffic is different. You need specific tools designed to show which processes are consuming bandwidth. Here are the practical options. nethogs nethogs remains the most straightforward tool for real-time network usage per process: sudo nethogs It displays incoming and outgoing…
Attaching and Mounting Xen DomU Disks in Dom0 There are times when you need direct access to a DomU’s disk from Dom0—for recovery, backup, or maintenance. This is straightforward with Xen’s block device tools, though the commands have evolved depending on your Xen version. Attaching the Disk The method depends on which Xen toolstack you’re…
Finding available disk space for a file on Linux When a program appends data to a file, you need to know how much space remains on the partition containing that file. This determines whether the file can grow or if you’re about to hit a capacity limit. Quick answer To find available space for a…
Padding Integers with Leading Zeros in Bash When you need to format an integer with leading zeros in bash, printf is the standard approach. This is useful for generating zero-padded IDs, filenames, or any formatted output. Using printf The basic syntax mirrors C’s sprintf: n=42 str=$(printf “%08d” “$n”) echo “$str” # Output: 00000042 Here, %08d…
Converting LaTeX to single-page HTML Converting LaTeX documents to HTML is useful for web publishing. Two main tools handle this conversion effectively: htlatex and latex2html. Both produce valid HTML output, though they have different strengths and limitations. Using htlatex htlatex is part of the tex4ht package and is generally more robust for modern LaTeX documents….
Converting HTML to text on Linux You have several options for converting HTML files to plain text, each with different strengths depending on your use case. html2text The most straightforward tool is html2text, available on most distributions: html2text input.html The converted text prints to stdout. Redirect to a file if needed: html2text input.html > output.txt…
Setting up ibus for Chinese input in Cinnamon on Fedora By default, ibus isn’t automatically started on Fedora with Cinnamon. You might try launching the daemon manually: ibus-daemon This starts the ibus service and adds an icon to your system tray, but you’ll find that Chinese input doesn’t work even when enabled through the tray…
Converting Unix Timestamps to Human-Readable Dates The Unix epoch (January 1, 1970 00:00:00 UTC) is the standard reference point for timestamps across Linux systems. When you need to convert a timestamp like 1349361711.169942 into a readable date, the date command is your primary tool. Basic Conversion The simplest approach uses date with the @ prefix:…
Replacing GDM with LightDM on Fedora GDM (GNOME Display Manager) can cause compatibility issues with Cinnamon, particularly around graphics rendering and session management. LightDM is a lightweight alternative that works better with Cinnamon and other desktop environments that don’t depend on GNOME’s ecosystem. Install LightDM First, install LightDM and the GTK greeter if not already…