If you need direct control over your firewall rules, you can disable firewalld and use iptables instead. This guide covers the setup process and best practices for maintaining persistent rules. Stop and disable firewalld If firewalld is currently running, stop it and prevent it from starting on boot: sudo systemctl stop firewalld sudo systemctl disable…
Parsing directory and filename components from an absolute path is a common task in systems programming. Linux provides dirname() and basename() functions for this purpose, but they have implementation-specific behaviors that can cause bugs if you’re not careful. Using dirname() and basename() The POSIX standard defines both functions, though the implementations vary. Here’s the safest…
When converting PostScript to PDF using ps2pdf with certain PDFSETTINGS options, you may hit this error: GPL Ghostscript 9.10: Set UseCIEColor for UseDeviceIndependentColor to work properly. Unrecoverable error: stackunderflow in .setdistillerparams This occurs when Ghostscript’s internal stack runs out of expected values during PDF distiller parameter processing. The root cause is usually conflicting color space…
When you have shared Makefiles included across multiple projects in different directory structures, relative includes break. If common.mk tries to include release.mk and both files are in a subdirectory like external/, the include fails because Make uses the current working directory, not the location of the including file. For example, this structure works fine: Makefile…
When a disk fills up or you’re doing a cleanup pass, finding the biggest files quickly saves a lot of time. Here are the practical approaches on Linux. Top 10 largest files in the current directory du -ah –max-depth=1 | sort -rh | head -n 10 Breaking this down: du -ah shows sizes for all…
GNOME Shell in GNOME 3 uses a specific font for the top bar, activities overview, and system notifications. You can customize these fonts using GNOME Tweaks or dconf to match your preferences. Using GNOME Tweaks (Recommended) # Install GNOME Tweaks sudo dnf install gnome-tweaks # Fedora sudo apt install gnome-tweaks # Ubuntu Open GNOME Tweaks…
Broken symbolic links accumulate over time and can cause confusion or errors when scripts rely on their targets. Identifying and cleaning them up is a regular maintenance task. Basic approach Use find with the -xtype l test to locate broken symlinks: find /path/to/directory -xtype l The -xtype l flag specifically matches symbolic links that point…
The passwd command is the standard tool for changing your password on Linux systems. It works across all distributions and doesn’t require administrative privileges for changing your own password. Basic password change Log in to your Linux system and run: passwd You’ll be prompted for: Your current password (to verify your identity) Your new password…
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 you faster provisioning, atomic snapshots, and…
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 repository configuration file: sudo tee…
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 file, use df: df -B1 /mnt/logs/app-log.log | tail -1…
Installing WordPress in a subdirectory keeps your site root cleaner and makes it easier to manage core files separately from content. Here’s how to configure WordPress so the admin and core files live in /wordpress while the site appears at your domain root. Creating the Subdirectory Structure First, create the WordPress directory and set proper…
MySQL replication lets you maintain synchronized copies of your database across multiple servers. This is essential for high availability, read scaling, and backups. Here’s how to configure it properly. Prerequisites You need at least two MySQL instances: a primary (source) and one or more replicas. Both should run the same or compatible MySQL versions. MySQL…
This error occurs when Fedora’s Anaconda installer cannot properly configure the bootloader, typically when it encounters conflicts between EFI and legacy boot modes or when the partition table format doesn’t match the system firmware expectations. Root Cause The error “you have not created a bootloader stage1 target device” usually indicates one of these issues: UEFI…
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…
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…
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…
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…
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. This is the problematic…
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 your system package manager or…