Distributed systems need consensus — a way for multiple nodes to agree on state despite failures and network partitions. Understanding the key algorithms behind consensus is essential for anyone designing reliable systems. Paxos and Its Variants Paxos is the foundational consensus algorithm, proven to tolerate Byzantine failures. It works in three phases: prepare, accept, and…
When should the authors anonymize themselves in a paper submitted to a conference for review? Several general concepts: Peer review is the evaluation of work by one or more people of similar competence to the producers of the work (peers). — Wikipedia Single-blind describes experiments where information that could introduce bias or otherwise skew the…
Deleted photos from your Samsung phone aren’t necessarily gone forever—they remain on disk until overwritten. Here’s how to recover them. Act quickly to preserve data The moment you realize photos are deleted, stop using your phone. Every new photo, message, or app activity risks overwriting deleted data. Turn off WiFi and mobile data to prevent…
Filtering RSS feeds lets you reduce noise and focus on content that actually matters. Whether you want to exclude posts mentioning certain topics or only see items matching specific keywords, there are several practical approaches depending on your setup. Using dedicated feed filtering services Feed43 (https://www.feed43.com/) is one of the most reliable web-based tools for…
Measuring the execution time of a function is useful for profiling and optimization work. OCaml provides straightforward tools for this. Basic approach with Unix.gettimeofday The simplest method uses Unix.gettimeofday(), which returns wall-clock time as a float with microsecond precision: let time f = let t = Unix.gettimeofday () in let res = f () in…
LXTerminal may fail to display Chinese characters correctly if fonts aren’t properly configured. This is typically a font availability or configuration issue rather than a terminal limitation. Check Your Font Setup First, verify that Chinese fonts are installed on your system. Install them if needed: Fedora/RHEL: sudo dnf install fonts-noto-cjk Debian/Ubuntu: sudo apt install fonts-noto-cjk…
iptables remains the standard firewall configuration tool on Linux systems, though many distributions now layer it with ufw or firewalld. Understanding the basics helps you troubleshoot, migrate, or work on systems without those abstractions. Understanding iptables Fundamentals iptables operates on three main chains: INPUT: rules for incoming traffic FORWARD: rules for traffic passing through the…
Logging connections that hit rate-limit rules helps you identify brute force attempts and troubleshoot legitimate clients that are being blocked. The standard approach is to create a dedicated chain that logs packets before dropping them. Create a logging and drop chain First, create a custom chain to handle logging and dropping: iptables -N LOGNDROP iptables…
Listing active services is essential for system monitoring and troubleshooting. Whether you’re investigating a hung process, checking if a daemon started correctly, or auditing what’s actually running on your system, knowing how to query service status quickly saves time. Basic Command The standard way to list running services across all modern Linux distributions is: systemctl…
ELPA (Emacs Lisp Package Archive) packages receive regular updates. Keeping your packages current ensures you have the latest features and bug fixes. Here’s how to upgrade ELPA packages in Emacs. Interactive Upgrade (Recommended) Use Emacs’s built-in package manager: Open the package list: M-x list-packages Press U to mark all upgradable packages Press x to execute…
Rate-limiting SSH brute-force attempts is essential for any server exposed to the internet. Using iptables with the recent module, you can drop connections from IPs that exceed a threshold in a given time window—for example, blocking IPs that attempt more than 6 connections in 60 seconds. Using iptables The recent module tracks connection attempts by…
Making firewall rules persistent across system reboots is essential for any production Linux system. While the original iptables-persistent approach works, modern systems typically use ufw (Uncomplicated Firewall) or firewalld, but understanding the underlying iptables mechanism is still valuable for lower-level control. Using iptables-persistent The iptables-persistent package automatically saves and restores your firewall rules during boot….
musl libc is a lightweight C library implementation that’s useful for creating statically-linked binaries, containerized applications, and embedded systems. It’s the standard C library in Alpine Linux and increasingly common in production environments. Installation from distribution repositories The simplest approach is installing musl from your distribution’s repositories: sudo apt update sudo apt install musl musl-dev…
When managing packages on Ubuntu or Debian systems, knowing what versions are available—and which one will be installed—is essential for dependency management and system stability. The aptitude command provides several ways to inspect package versions. Check all available versions of a package The most straightforward approach is to use the versions subcommand: aptitude versions package-name…
Xterm doesn’t send Alt key escape sequences by default, which breaks Alt-based keybindings in Vim, Emacs, shell readline, and other applications. Here’s how to fix it across different terminal setups. Xterm Configuration Add this to your ~/.Xresources file: xterm*metaSendsEscape: true Then load the changes and restart xterm: xrdb -merge ~/.Xresources xterm & This tells xterm…
When backing up with rsync, you often need to skip directories like cache/, node_modules/, or .git/ that appear at multiple levels in your directory tree. Listing every instance individually is impractical, but rsync’s exclude patterns handle this elegantly. Basic exclude syntax The simplest approach uses –exclude with a directory name pattern: rsync -avxP –exclude=cache/ /path/to/src/directory/…
When you create a new branch locally and try to git pull, you’ll hit this error if the branch doesn’t have upstream tracking configured: You asked me to pull without telling me which branch you want to merge with, and ‘branch.dev-harry.merge’ in your configuration file does not tell me, either. This happens because Git doesn’t…
When you need to audit disk usage or understand directory structure, counting files in each subdirectory is a common task. This is especially useful when dealing with large directory trees where you need a quick overview of distribution. The Basic Approach The simplest method uses a loop with find and wc: for i in */;…
When you run cat /etc/resolv.conf on a modern Linux system, you’ll often see nameserver 127.0.0.1 or 127.0.1.1 pointing to localhost. This doesn’t mean you’re actually using your ISP’s DNS directly — it usually means your system is running a local DNS stub resolver or caching service like systemd-resolved or dnsmasq. To find out which actual…
A USB drive that’s mounted as read-only is frustrating — you can read files but can’t write, delete, or modify anything. This usually happens due to filesystem issues, hardware problems, or missing drivers. Check the Current State First, identify how the drive is mounted and what filesystem it uses: lsblk -f Look for your USB…