Xen remains in production use across several platforms (AWS EC2, Citrix Hypervisor), though KVM has become the default hypervisor for most Linux distributions. This approach is most relevant if you’re managing legacy Xen infrastructure or working with providers that standardize on it. When managing multiple Xen DomU virtual machines with similar configurations, creating individual configuration…
Accessing a remote desktop environment on a Linux server securely requires proper tunneling. While SSH X11 forwarding works for single applications, VNC provides a full graphical desktop session. By combining VNC with an SSH tunnel, you encrypt all traffic and can work around firewall restrictions that only allow port 22. Why VNC Over SSH? VNC…
DNS caching helps reduce lookups but sometimes you need to clear it after DNS changes, certificate updates, or to troubleshoot resolution issues. Modern Linux with systemd-resolved Most contemporary Linux distributions use systemd-resolved as the default DNS resolver. Flush the cache with: sudo systemctl restart systemd-resolved Or use the resolvectl command: sudo resolvectl flush-caches To verify…
Xen remains in active production use—particularly in cloud infrastructure like AWS EC2 and Citrix Hypervisor—though KVM has become the standard hypervisor for most Linux distributions. If you’re managing legacy Xen deployments, this guide covers the essential steps for cloning VBD-based DomU instances. Prerequisites Before starting, ensure: The source VM is powered off (critical to avoid…
Git and SSH integrate seamlessly for version control infrastructure. An SSH-based Git server works well for small teams where all members are trusted and have administrator-level access to all repositories. This approach is straightforward to deploy, but lacks fine-grained access control. For teams that need role-based repository access or audit trails, consider dedicated tools like…
ISO images are sector-by-sector copies of optical media stored as binary files. They’re useful for archiving DVDs or creating portable copies without keeping physical disks around. On Linux, several tools can accomplish this—dd is the simplest, but modern alternatives offer better features. Using dd to Create an ISO Image The most straightforward approach uses dd:…
DNS lookups can be a bottleneck in Firefox browsing performance. Here are practical methods to optimize DNS resolution and related network behavior. Disable IPv6 (if not needed) If your network doesn’t use IPv6, disabling it can eliminate unnecessary lookup delays. In Firefox, navigate to about:config and set these preferences: network.dns.disableIPv6 → true This prevents Firefox…
To connect to HKUST’s sMobileNet wireless network via NetworkManager, you’ll need to configure WPA2 Enterprise authentication with PEAP. This guide covers the required settings. Network Settings Configure the following parameters in NetworkManager: Basic Settings: SSID: sMobileNet Wireless security: WPA & WPA2 Enterprise Authentication method: Protected EAP (PEAP) Authentication Details: Anonymous identity: (leave empty) PEAP version:…
Mounting an ISO on Linux requires a loop device. Modern systems support this directly with mount: sudo mount -o loop /path/to/image.iso /mnt/mount-point Or use the -t iso9660 option for explicit filesystem specification: sudo mount -t iso9660 -o loop /path/to/image.iso /mnt/mount-point To unmount: sudo umount /mnt/mount-point For temporary mounts that don’t require persistence across reboots, consider…
After running on MediaWiki, we migrated back to WordPress. Both platforms have their strengths, but WordPress proved to be the better fit for our site’s goals. What WordPress Does Better for This Site Plugin Ecosystem and Content Discovery WordPress’s plugin landscape is significantly deeper than MediaWiki’s. The YARPP (Yet Another Related Posts) plugin and its…
Crontab controls what runs and when. Each crontab entry has this format: .—————- minute (0-59) | .————- hour (0-23) | | .———- day of month (1-31) | | | .——- month (1-12) OR jan,feb,mar,apr … | | | | .—- day of week (0-6) (Sunday=0 or 7) OR sun,mon,tue … | | | | |…
File compression is a routine task in Linux administration. You’ll encounter several tools, each with different tradeoffs between compression ratio, speed, and compatibility. This guide covers the most common compression formats: gzip, bzip2, 7z, xz, and zip. The examples below assume you’re compressing a directory called dir. Each tool supports compression level options — you…
TeraSort is Hadoop’s standard benchmark for measuring distributed sorting performance across clusters. It consists of three components: TeraGen generates random input data, TeraSort performs the distributed sort, and TeraValidate confirms the output is globally sorted. Modern Hadoop deployments typically run on Hadoop 3.x or higher, with improvements in YARN resource management, better performance tuning options,…
Modern datacenters rely on distributed storage and processing systems designed to handle massive datasets across clusters of commodity hardware. Understanding these systems is essential for anyone working with infrastructure at scale. Here’s an overview of the major architectures and implementations you’ll encounter. Storage Systems Google File System (GFS) and successors GFS established the foundation for…
Hadoop 1.x reached end-of-life in 2014 and is no longer maintained. This post documents a deprecated architecture for historical reference only. For new deployments, use Hadoop 3.x+ with YARN, which offers significant improvements in resource management, multi-tenancy, and reliability. See the Apache Hadoop documentation for current versions. For managed services, consider AWS EMR, Google Dataproc,…
Gitosis provides a lightweight way to manage Git repositories and user access on a self-hosted server. This post covers user management, repository configuration, and access control. For initial server setup, refer to your Gitosis installation documentation. Adding a New User Each user needs an SSH key pair for authentication. The user generates their key locally:…
Gitosis is unmaintained and shouldn’t be used for new deployments. Use Gitolite or Forgejo instead. This guide covers Gitolite, which provides fine-grained access control, is actively maintained, and handles multiple repositories under a single system user. Prerequisites A server running Linux (Debian, Ubuntu, CentOS, or similar) SSH access to the server with sudo privileges A…
Hadoop daemons communicate over specific TCP ports that you’ll need to know for cluster setup, firewall configuration, and application development. These ports are configurable but come with sensible defaults in Hadoop 3.x. HDFS Ports Service Port Configuration Property Purpose Namenode HTTP UI 9870 dfs.namenode.http-address Web UI and metadata operations Namenode HTTPS UI 9871 dfs.namenode.https-address Secure…
Running benchmarks after a Hadoop installation helps validate that your cluster works correctly and gives you baseline performance metrics. The Sort benchmark is a standard test that exercises the MapReduce execution engine and HDFS, making it useful for stress-testing both the distributed storage layer and computation framework. What the Sort Benchmark Does The Sort benchmark…
Hadoop 3.x remains the current stable version with YARN improvements, HDFS federation, and erasure coding. Hadoop 1.x and 2.x are no longer maintained. For new deployments, evaluate whether Hadoop fits your needs or if managed services like AWS EMR, Google Dataproc, or Azure HDInsight better suit your infrastructure. This post covers common configuration mistakes and…