Category: system admin

WordPress: a recipe for switching from Apache to Nginx.

Posted by – Monday 2016-05-23

This blog runs on a bunch of software items, among them an instance of the WordPress content management system and a web server. For years I have trusted on the Apache HTTP server, despite I never liked it. Recently I switched to Nginx, a web server that is gaining a lot of traction, particularly among the busiest web sites [1, 2].

Why did I do this switch? For some reason unknown to me, some weeks ago Apache’s appetite for RAM memory went through the roof. None of the solutions I tested worked, including an update from version 2.2 to 2.4. Thus, I had a blog that was unusable: almost every request raised a HTTP 500 error. The following data provides some context: this blog is a low traffic one – it serves an average of 70 pages per day – and it is hosted on an inexpensive VPS that has 512 MB of RAM memory.

The solution I took was switching to Nginx, and it worked.

LEMP: Linux + Nginx + MySQL + PHP

This post is a quick-and-dirty recipe for switching an existing WordPress blog from the Apache web server to Nginx in a machine running a Debian 7 operating system. There is no original research: the instructions given here are taken from several web pages about Nginx, PHP and WordPress and put together here; and it is likely that there is room for improvement.


Revisiting ECW support to GDAL via plugins: a patch.

Posted by – Wednesday 2012-05-02

In the blog post “Adding ECW support to GDAL via plugins” (February 2011) I shared the experiences I had to get the GDAL library able to work with this proprietary format.

Some days ago I had to repeat the task, and that recipe did not work. Under Debian 6 I was unable to build libecwj2-3.3.tar.gz for GDAL 1.6.3 using GCC 4.4.5. One year ago the environment was different: Debian 5, GDAL 1.5.2 and GCC 4.3.2.

Fortunately, via Google I found “Patch to build libecwj2-3.3.tar.gz with GCC 4.1” on OSGeo’s gdal-dev mailing list, which gave me a clue to solve the problem.


Adding a Fibre Channel disk to a Debian Linux server.

Posted by – Sunday 2012-04-29

Spanish economy is not doing well; actually, it is sinking. Budgets are shrinking and therefore in many organizations reusing old computers has become mandatory for IT staffs.

Giving old computers a new life may raise some curious problems. At my work place we decided to reuse a HP Proliant server which was bought circa year 2005. It has a four-core Itanium processor and a decent amount of RAM memory, making it suitable for a task like serving web pages dynamically generated. The problem is its small storage capacity by today’s standards: only two hard disks, each one having 36 GB of storage.

QLogic Fibre Channel

Fortunately, the server has two HP QLogic ISP2312 Fibre Channel adapters. Thus storage shortage can be solved without buying additional hard disks (assuming they are available for sale). Instead, the needed storage is added via Fibre Channel (FC).


A short note about setting Apache Tomcat 7 environment variables under Debian 6.

Posted by – Sunday 2012-04-22

In this post we will see a way of setting Apache Tomcat, version 7, environment variables when running under Debian 6.

Let’s suposse that Apache Tomcat – Tomcat for short – has been installed in the directory TOMCAT_DIR and that we want to set the used Java virtual machine and the amount of used RAM memory.


Adding ECW support to GDAL via plugins.

Posted by – Sunday 2011-02-27

In this post we will see how to add to the Geospatial Data Abstraction Library [1] (GDAL) library limited support [note 1] for ER Mapper’s Enhanced Compression Wavelet (ECW) format[2]. The environment will be an Ubuntu Linux operating system.

The ECW format has become very popular because it achieves high compression ratios at the expense of small amounts of RAM memory and computing time. Another remarkable feature of this format is selective decompression, that is, it is “able to selectively decompress a portion of digital imagery while viewing the image, and to selectively decompress the image at different levels of detail (as the user zooms in or out the image view)” [3]. Other popular compression formats like TIFF or JPEG do not feature selective decompression; the whole image must be decompressed before viewing it, a seriuos issue when working with gigabyte sized images like orthophotographs.

The ECW format is propietary and, thus Linux distros like Debian or Ubuntu do not provide support for ECW in GDAL, even in their selections of non-free packages. That is the reason of the ‘install recipes’ shown in this post.

In the first section we will see how to compile this library, creating a .deb package useful for future installations. In the second section we will see how to install the GDAL’s ECW plugin, also needed to get GDAL able to read ECW files.

Come abilitare il supporto ai file ECW in GDAL e visualizzarli in GRASS e QGIS“, written in Italian language, is the article this one is based on.