Questions and answers.
RSA (Rivest–Shamir–Adleman) underpins SSH authentication, TLS certificates, code signing, and encryption across most Linux systems. OpenSSL is the standard tool for generating and managing these keys. Verify OpenSSL Installation OpenSSL is bundled with virtually all distributions. Check your version: openssl version If it’s missing: # Ubuntu/Debian sudo apt-get install openssl # RHEL/CentOS/Fedora sudo dnf install…
SSH keys provide secure, password-less authentication to remote systems. Choosing the right algorithm matters for security, compatibility, and operational stability. Generate an Ed25519 Key Pair Ed25519 is the modern standard for SSH key generation. It offers stronger security properties than RSA, faster operations, and smaller key sizes. ssh-keygen -t ed25519 -C “your_email@example.com” You’ll be prompted…
You don’t need to fully extract a .tar archive just to read one file inside it. The tar command can stream individual files directly to stdout, which saves time and disk space—especially useful for large archives. Basic syntax tar -xOf archive.tar path/to/file.txt The flags break down as: -x: Extract mode -O: Write to stdout instead…
Wget is a reliable command-line tool for downloading entire websites for offline viewing, archival, or testing. It preserves the full site structure—HTML, images, CSS, JavaScript—and maintains the original directory layout. Basic Mirroring Command The core command to mirror a website: wget –mirror –convert-links –adjust-extension –page-requisites –no-parent https://example.com Flag Breakdown –mirror: Enables recursive downloading with time-stamping…
By default, rsync connects as your standard user. When you need to write to protected directories like /etc, /var/www, or other root-owned locations, use the –rsync-path option to invoke rsync with sudo privileges on the remote side. Basic syntax rsync -avz –rsync-path=”sudo rsync” local-file user@remote:/protected/path This tells the remote server to execute rsync under sudo….
You opened a system config file in Vim without sudo, made changes, and hit :w to save. Permission denied. Retyping everything isn’t happening. The Solution: :w !sudo tee % From Vim’s normal mode, type: :w !sudo tee % This pipes your buffer through tee running as root: :w — write the current buffer ! —…
Renaming a Git branch involves three steps: rename locally, push the new branch, and delete the old remote branch. How you do this depends on whether you’re working from the command line or your Git hosting platform’s UI. Rename the branch locally The simplest command renames a branch in your local repository: git branch -m…
By default, GNOME Shell restricts theme customization to GTK application themes. To modify the shell itself — the top bar, Activities overview, lock screen, and system UI elements — you need the User Themes extension. This remains the primary method for shell theming across Ubuntu and GNOME. Installation and Setup Install the required packages: sudo…
The simplest way to display the date and time in a different timezone is with the TZ environment variable: TZ=’America/New_York’ date This temporarily sets the timezone for that single command execution without affecting your system settings. The change applies only to that invocation. Chain multiple timezone checks easily: TZ=’America/New_York’ date TZ=’Europe/London’ date TZ=’Asia/Tokyo’ date Custom…
Emoji rendering at incorrect sizes in Thunderbird usually comes down to font configuration. Unlike browsers that inherit system emoji rendering, Thunderbird manages its own font stack, which can drift out of sync with your system fonts or get corrupted in Thunderbird’s cache. Install a Color Emoji Font Start by ensuring you have a proper color…
Plymouth manages the splash screen (boot logo) displayed during Ubuntu startup and shutdown. Switching themes involves selecting a Plymouth theme, regenerating the initramfs, and verifying the change takes effect on reboot. List available themes Check what Plymouth themes are installed and available: apt search plymouth-theme To see only installed themes: apt list –installed | grep…
GNOME’s natural scrolling setting can be frustrating — especially when the GUI option is missing or doesn’t apply to your mouse while leaving your touchpad alone. The issue usually comes down to your session type, GNOME version, and how input devices are registered on your system. Check your session type first Before troubleshooting, verify whether…
Ubuntu MATE ships with the MATE desktop environment, but you might prefer GNOME’s modern interface and tighter integration with system tools. Installing GNOME alongside MATE is straightforward and lets you switch between them at login without removing either one. Installation Update your package list and install the GNOME desktop package: sudo apt update sudo apt…
Zlib is a foundational open-source compression library implementing the DEFLATE algorithm. It powers gzip, PNG, HTTP compression, and countless applications. While Ubuntu’s package repositories provide pre-built binaries, compiling from source lets you use the latest version, customize the installation path, enable specific compile-time features, and maintain multiple versions simultaneously. This guide covers building zlib on…
Linux input method frameworks have matured significantly over the past few years. Ubuntu offers two solid options: IBus (integrated into GNOME by default) and Fcitx5 (more feature-rich and actively maintained). This guide covers both approaches and helps you choose the right one for your setup. IBus: Quick Setup for Basic Use IBus comes pre-installed on…
Both FS_IOC_GETFLAGS and FS_IOC_FSGETXATTR retrieve inode attributes, but they differ in scope, design, and what they’re meant to expose. Understanding which to use depends on your filesystem, compatibility requirements, and what metadata you actually need. Historical context and design constraints FS_IOC_GETFLAGS originated with ext2/ext3 as a simple interface to query inode flags. It became so…
Local port forwarding on the same host requires understanding how netfilter processes packets based on their origin. The critical distinction: traffic from external sources hits the PREROUTING chain, but packets originating locally traverse the OUTPUT chain instead. Miss either one, and your forwarding won’t work. The core problem When you forward UDP port 500 to…
Traditionally, tools like strace used ptrace to monitor system calls. While effective for development debugging, ptrace stops the entire process for every syscall, causing 2-10x slowdown. This makes it unsuitable for production workloads where you need real-time visibility without tanking performance. Modern Linux offers significantly faster alternatives through eBPF (Extended Berkeley Packet Filter), which runs…
PHP lets you call functions dynamically when you don’t know the function name until runtime. This is essential for plugin systems, routing handlers, API dispatchers, and configuration-driven logic. The approach you choose affects both performance and safety. Direct Variable Function Invocation The simplest approach treats a string variable as a callable: $func = ‘strlen’; echo…
The built-in pdb module is Python’s equivalent to gdb — a command-line debugger that lets you step through code, set breakpoints, inspect variables, and control execution flow. It’s essential for server-side debugging and situations where IDE graphical debuggers aren’t available. Starting a pdb Session Run a script through pdb directly: python -m pdb prog.py arg1…