Sending POST Requests in Go
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Querying Maximum Temperature Across Linux Server Sensors
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EncFS on Android: Setup and Usage Guide
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Looking up Hostnames from IP Addresses in /etc/hosts on Linux
When you need to reverse-lookup an IP address against your local /etc/hosts file, several tools can help. This is different from a full DNS reverse lookup — you’re checking only against the static mappings on your local system. Why this matters By default, most hostname resolution tools check /etc/hosts first before querying DNS servers. If…
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Limit SQL Query Results to N Rows in MySQL
The LIMIT clause in MySQL lets you control how many rows a SELECT query returns. This is essential for pagination, performance tuning, and working with large datasets. Basic LIMIT Syntax To return only the first N rows from a table: SELECT * FROM qa_users LIMIT 10; This returns the first 10 rows from the qa_users…
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Configuring Zimbra Web Service Hostname and Port
Zimbra’s web interface needs proper hostname and port configuration to function correctly, especially when you’re deploying behind load balancers, reverse proxies, or in clustered environments. Viewing Current Configuration Check your current Zimbra web service hostname and port settings: zmprov getServer $(zmhostname) zimbraMailPort zmprov getServer $(zmhostname) zimbraMailSSLPort zmprov getServer $(zmhostname) zimbraAdminPort You can also query the…
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Getting Your Zimbra Version
The most direct way to check your Zimbra installation version is through the zmcontrol utility: zmcontrol -v This returns the version string of your Zimbra deployment. Run this command on any Zimbra server in your environment — the output will be identical across all nodes in a cluster. Alternative Methods If zmcontrol isn’t available or…
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Disabling DHCP in dnsmasq on Linux
If you’re running dnsmasq primarily for DNS resolution and don’t need its DHCP server capabilities, you’ll want to disable DHCP while keeping DNS functional. This is a common configuration for DNS-only setups or when another service handles DHCP. Default dnsmasq behavior By default, dnsmasq ships with DHCP disabled. However, many distributions include preconfigured DHCP settings…
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Getting the Hostname in Go
Go’s os package provides a straightforward function to retrieve the system’s hostname: package main import ( “fmt” “os” ) func main() { hostname, err := os.Hostname() if err != nil { fmt.Println(“Error:”, err) return } fmt.Println(“Hostname:”, hostname) } The os.Hostname() function returns a string containing the hostname and an error value. Always check the error—it…
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Getting a Node’s Hostname in Python
There are several ways to retrieve the hostname of the current machine in Python, each with different use cases. Using socket.gethostname() The simplest and most common approach is the socket module, which is part of Python’s standard library: import socket hostname = socket.gethostname() print(hostname) This returns the hostname as a string. On most systems, this…
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Getting the Current Epoch Timestamp in Java
Java provides multiple ways to get the current time as an epoch value. The right approach depends on whether you need milliseconds, seconds, or nanosecond precision, and whether you’re working with UTC or time zones. Using Instant for UTC timestamps The most straightforward method is Instant.now(): Instant now = Instant.now(); long epochSeconds = now.getEpochSecond(); long…
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Java REPL Tools: A Practical Comparison
Java has several solid REPL implementations available. Here are the main options and how to use them. jshell (Official) The best choice for most users is jshell, included in JDK 9+. It’s the official interactive shell for Java and comes with every modern Java installation. Start it immediately: jshell Basic usage: jshell> long ts =…
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Cannot Start VM: Missing Default Network
After a libvirt upgrade, VMs fail to start with the error: error: Failed to start domain kvm1 error: Network not found: no network with matching name ‘default’ This happens when the default NAT network (virbr0) isn’t automatically created during the upgrade. Quick fix: Restore the default network The fastest solution is to recreate the default…
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Ubuntu GUI Performance Slowdown: Causes and Fixes
When running Ubuntu on older servers like Dell PowerEdge systems with legacy graphics cards (Matrox G200eR2, etc.), you may encounter extremely slow desktop performance. The issue typically stems from the X server falling back to unoptimized drivers or incorrect video mode detection. Identifying the problem First, check your current graphics configuration: lspci | grep -i…
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Redirect Non-WWW URLs to WWW with .htaccess
The most common approach is using Apache’s mod_rewrite module. Add this to your .htaccess file in your document root: <IfModule mod_rewrite.c> RewriteEngine On RewriteCond %{HTTP_HOST} !^www\. [NC] RewriteCond %{HTTP_HOST} !^$ RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [L,R=301] </IfModule> This uses a 301 permanent redirect, which tells browsers and search engines that the www version is canonical. The conditions…
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Handling Spaces in File Paths with rsync
Spaces in file and directory paths are a common source of rsync failures. When paths contain spaces, the shell interprets them as argument separators unless you properly escape or quote them. Here’s how to handle this correctly. The core issue When rsync receives an unquoted path with spaces, the shell splits it at each space….
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How to Install aria2 on CentOS 7
aria2 is a lightweight, multi-protocol download manager that supports HTTP(S), FTP, BitTorrent, and Metalink protocols. It’s particularly useful for resumable downloads, parallel connections, and command-line automation. Prerequisites You’ll need root or sudo access. This guide covers CentOS 7, CentOS Stream, and Rocky Linux 8+. For older systems still on CentOS 7, package availability may be…
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Connecting to a Remote Server with VNC
VNC (Virtual Network Computing) provides a graphical remote desktop connection to Linux servers. It’s straightforward to set up and useful when you need GUI access to a headless or distant system. Installation On the server side, install a VNC server package. TigerVNC is the most reliable choice across distributions: Debian/Ubuntu: sudo apt install tigervnc-server tigervnc-common…
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Installing SSHFS on CentOS 7
SSHFS isn’t available in the default repositories on most RHEL-based distributions. If you try to install it directly, you’ll get an error: # yum install sshfs No package sshfs available. Error: Nothing to do The package lives in EPEL (Extra Packages for Enterprise Linux), so you need to enable that repository first. Enable EPEL For…
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Configuring CONFIG_HZ in the Linux Kernel
CONFIG_HZ sets the kernel’s internal timer interrupt frequency (measured in Hz). This determines how often the kernel’s scheduler runs and how fine-grained process preemption can be. The default value is typically 250 Hz on most distributions, though some set it to 1000 Hz for lower latency workloads. Higher CONFIG_HZ values (like 1000 Hz) reduce scheduling…