Linux related articles, news, information, etc

Release hold queue email in Postfix – postsuper

How to flush Postfix’ mail queue from the command line? Easy, use the Postfix postsuper command as explained in this post. The postsuper command controls different types of queues in the Postfix mail system, like the deferred or hold queue. This post shows you some Postfix queue operations to maintain your mail servers.

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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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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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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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Turn off swap

How to turn off swap in Linux. Not every Linux server I administer needs to have a swap partition and to start swapping. For instance, the MySQL servers I maintain all have more than enough RAM on board to do their work. Yet, when a swap partition is enabled Linux starts swapping, which may degrade MySQL database performance…

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New Open-Xchange merger: PowerDNS

Open-Xchange stays on the takeover path: On stage live at World Hosting Day in Rust today Rafael Laguna (CEO, Open-Xchange) had the privilege of announcing that we’ve done it again – we’re merging with another pioneer in the open source and domain communities, Netherlands-based software company PowerDNS.

Read the announcement: Open-Xchange Power-ing up

Monit monitoring on Ubuntu 14.04 VM on Hyper-V

Monit monitoring for websites and services, on an Ubuntu 14.04 LTS VM, hosted on a Windows Server 2012 R2 or Windows 8.1 Hyper-V. This post is about setting up a Monit monitoring service. Monit is a free and open source service monitoring application which can perform various event-based actions. Monit can send email notifications, restart a service or application, or take other responsive actions. We set Monit up on a Ubuntu 14.04 VM, built on Hyper-V. And we use Monit to monitor several websites, and send out notifications on downtime.

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How to restore a deleted Open-Xchange context?

How to restore, or recover, an accidentally deleted OX context. If you’ve accidentally deleted an Open-Xchange context (contextid), then that is bad… Here is how to recover a deleted OX context and filestore… Assuming you make backups of course.

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Convert decimal to hex in Bash?

A quicky for my archives: Convert decimal to hex in Bash, and hexadecimal to decimal. In mathematics and computing, hexadecimal (also base 16, or hex) is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0-9 to represent values zero to nine, and A, B, C, D, E, F (or alternatively a-f) to represent values ten to fifteen. If you want to convert hexadecimal values to decimal and decimal values to hexadecimal, here’s how. All on the bash prompt…

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Sysadmins of the North goes global!

How to set up a global Geolocation DNS load balancing Varnish Cache Content Delivery Network with Bind9, geo-ip database, Varnish Cache and DigtalOcean. DIY High-Availability for your website!

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How to delete all MAILER-DAEMON emails in Postfix queue

How to delete all MAILER-DAEMON emails from your Postfix queue, when it matches a sender or recipient email address condition. When a large scale spam run was sent through your mail servers, you need to clean up and remove those spam messages. Doing so guarantees normal, valid email messages being sent quickly, and the spam messages never leave your queue. In Postfix, there are various similar commands to delete messages from the Postfix mail queue. Based on the Message-ID and/or email address…

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Ssh shorthand name for hostnames

Ssh shorthand name for hostnames. How to use shorthand names for hostnames with ssh? You don’t always want to typ in complete hostnames when using ssh to remote hosts. Here is how to configure and use shorthand hostnames with ssh.

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Redirect HTTP to HTTPS on Apache 2.4

The last few day’s I’ve been toying with Nagios, setting up a monitoring system. An Apache redirect to HTTPS was one of the tasks I wanted to accomplish. This would redirect the Nagios vhost from HTTP to HTTPS using an Apache 2.4.6 VirtualHost, and no resource expensive rewrite would be necessary.

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Mount an Open-Xchange InfoStore on Linux

Open-Xchange is an all-in-one Groupware solution, providing not only email, but also a CalDAV calendar, tasks, file- or InfoStore and an online document editor. All shareable with other users. The InfoStore is used to save documents online, in the cloud. This article is about accessing and mounting your Open-Xchange remote WebDAV InfoStore file share, on Linux with mount.davfs or Dolphin GUI file manager.

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