Sysadmins of the North

Technical blog, where topics include: computer, server, web, sysadmin, MySQL, database, virtualization, optimization and security

Author: Jan Reilink (page 6 of 15)

Optimize WordPress MySQL tables through Cron, behind the scenes

To regularly optimize my WordPress database tables, I created a small plugin that utilizes the WordPress Cron feature. This comes in handy to perform database optimization for WordPress on a regular basis, without forgetting about it. Just activate and enjoy. And here is the plugin code …

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HackRepair.com’s Bad Bots .htaccess in web.config for IIS

Jim Walker from HackRepair.com posted a 2016 version of his Bad Bots .htaccess on Pastebin. I offered Jim to translate his Bad Bots .htaccess to web.config, to be used with Windows Server IIS. And here it is, learn to protect your WordPress website with this web.config file!

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IIS URL Rewrite “Rewrite Module error: Expression contains a repeat expression”

How to fix the URL Rewrite Module error “Rewrite error: Expression contains a repeat expression” on Windows Server IIS.

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Cracking PHP rand()

Sjoerd Langkemper writes about Cracking PHP rand(): Webapps occasionaly need to create tokens that are hard to guess. For example for session tokens or CSRF tokens, or in forgot password functionality where you get a token mailed to reset your password. These tokens should be cryptographically secure, but are often made by calling rand() multiple times and transforming the output to a string. This post will explore how hard it is to predict a token made with rand().

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Recursive scp and symlinks

Recursive scp without following symbolic links. TL;DR: when using recursive scp, symbolic links aren’t preserved and are copied as if they are normal directories. So you have to look for another solution to recursively transfer symlinks over ssh. Here is one: Tar over ssh!

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Deny vulnerable WordPress plugins using Windows Server File Server Resource Manager’s File Screens

Using Windows Server File Server Resource Manager‘s File Screens you can block vulnerable WordPress plugins from being saved on your IIS web server. In the following example, you’ll learn how to block WP DB Backup plugin system-wide on Windows Server, read on…

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Install Varnish Cache on CentOS 6.7

In this article I’ll show you how to install Varnish Cache on CentOS, version 6.7 in this case. Varnish is a web application accelerator also known as a caching HTTP reverse proxy. You install it in front of any server that speaks HTTP and configure it to cache the contents. Because Varnish Cache is really, really fast, web applications like WordPress, Drupal and Joomla can greatly benefit from Varnish Cache.

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Install Elasticsearch on CentOS 6.7

How to install Elasticsearch on CentOS 6.7. Elasticsearch is a highly scalable open-source full-text search and analytics engine. It allows you to store, search, and analyze big volumes of data quickly and in near real time. In this article we’ll go over the steps to install Elasticsearch on CentOS 6.7.

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Minify WP-Super-Cache HTML cache files: WPSCMin a WP-Super-Cache plugin

The WordPress WP-Super-Cache cache plugin doesn’t minify HTML cache files, which I find a disadvantage. Knowing minify libraries, I went looking for an existing solution (why reinvent the wheel?), and found one: WPSCMin. Read on …

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SQL Server versions list

How to Identify Your SQL Server version and edition.

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Generate pseudo-random passwords with OpenSSL

OpenSSL comes in handy when you need to generate random passwords, for example for system accounts and services. In this short post I’ll give you a quick example on how to generate random passwords with OpenSSL in Linux (Bash), Windows and PHP…

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Always_populate_raw_post_data setting in PHP 5.6 & Magento 2.0

Does Magento 2 throw an error about always_populate_raw_post_data being set to 0? And are you having problems installing or updating Magento with PHP 5.6 and PHP 7? Then read on, because here is how to fix upgrades to Magento 2.0 in PHP 5.6 and higher: PHP 7+.

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PowerShell return value, exit code, or ErrorLevel equivalent

Here is how you can verify whether an external command in PowerShell was executed successfully or not by its errorlevel. Simply by verifying PowerShell’s return value, or exit code…

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RewriteProxy with .htaccess in IIS

Rewrite and proxy HTTP requests in IIS using a .htaccess

In my case scenario, I had to proxy requests in IIS, because a website was moved from web server A to B, and the DNS wasn’t updated yet. All HTTP requests for the moved website are handled in IIS’ Default Web Site; that’s the wildcard host, and the original host no longer existed there. We needed to match our website and proxy those requests to the new IIS web server. This can either be done using a proxy with URL Rewrite, IIS Application Request Routing (ARR), or a .htaccess file handled by Helicon Ape.

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Get Hyper-V guest serial number with PowerShell

How to retrieve the Hyper-V virtual machine’s serial number with PowerShell? Sometimes you need to have the serial number of a Hyper-V virtual machine (VM, or guest). We, for instance, use this serial number in our automatic, unattended deployment of the guest operating system. But then you need to know how to find this serial number…

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