Jan 192015

Other posts in this blog have already covered the procedure to add an interactive map to a web page either using the Google Maps API or else the HERE Maps API.

Leaflet is an open source alternative equally valid to put a map on a page. The Leaflet API allows adding our own information layers to the map, customize the design, and adapt the map to our requirements in other ways.

This post provides an introduction to the main characteristics and functionality of Leaflet.

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 Posted by at 6:28 pm
Jan 182015

Sometimes, while editing a text file with the vim editor, we might need to enter, search and/or replace characters not available in our keyboard, such as æ, å, ě, … or non-printable characters such as controls characters ^A, ^B, … or characters with hexadecimal codes between 0x7F and 0xFF.

This post goes through some of the possibilities in vim to work with those characters.

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 Posted by at 8:20 pm
Jan 152015

Any server connected to internet will sooner or later become the target of hackers, that will try every possible vulnerability to break in and take control of it, to use it for their own purposes.

To protect the server as much as possible, it is common using some kind of firewall. In cases where an external firewall is not feasible or affordable, the iptables package that comes as default in most linux distros is one good choice to implement this functionality.

This post explains how to install and configure iptables on a Debian/Ubuntu system, together with fail2ban, that automates the detection and handling of brute force attacks.

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 Posted by at 9:01 am
Jan 062015

Nowadays, the webmasters of most websites must take into account the growing number of users browsing the web from mobile devices, smartphones and tablets.

The screen size and resolution of these devices is generally much smaller than that in the desktop and laptop devices that were taken as reference at the time the design of most websites was created.

Ideally, the design of a web site should be responsive, detecting the characteristics (screen size, resolution) of the device and adapting the layout consequently. The first step in this direction was the specification of the viewport meta tag, thas has already been explained in other articles in this blog. Currently, a more precise control on the responsive layout can be achieved using CSS media queries. This technique allows the designer to setup sets of CSS rules specific for different screen resolutions, device orientations, etc. In this way, the design can be made to adapt to different devices using the same HTML code for the page.

This post gives an overview of the usage of CSS media queries in the design of a web site.

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 Posted by at 10:12 pm
Jan 042015

With the arrival of the smartphones, that allow the user to navigate the internet, the way new websites are designed has changed. Most of new designs are “responsive”, that is, they adapt their layout to the dimensions of the screen where they are being displayed.

But, for many of the websites that existed previously, the change to a responsive design is not an easy task. Nevertheless, there are some minor changes that can be done to a non-responsive design, that may improve the rendering of a site on screens that are smaller than the target resolution of the original design.

This post explains some of the possible design changes that can be done on a non-responsive website.

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 Posted by at 8:52 pm
Dec 292014

Sometimes, a process that we have started from a terminal might be taking longer to complete than what we had estimated. The process has already been running for a long time, and we want it to continue executing, but we need to detach the process from the terminal to close the interactive session.

This post explains how to detach from the terminal a process that has been started from a bash shell on a linux system.

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 Posted by at 1:47 pm
Dec 032014

A web site that delivers any type of service, might need to implement some kind of user signup / login functionality. In this way, registered users could be granted access to extra functionalities not available to anonymous users.

In a previous post we have already covered a possible implementation of this signup / login functionality on a generic web server, using a set of PHP scripts. This post focuses on the specific case of a standalone WordPress installation.

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 Posted by at 3:37 pm
Nov 202014

Most email services implement several verification procedures on incoming email to ensure that it is legitimate, and prevent their users’ inboxes from being flooded with unwanted email (spam).

For instance, Google Gmail, among other tests, verifies that the incoming email is signed with DKIM. Servers sending email to gmail users that do not implement this signing may find that the emails sent are flagged as spam by Google Gmail servers, are delivered to the spam folder of the recipient, or are just discarded.

This post goes through the details of the implementation of the DKIM digital signature on a Postfix mail server running on a linux Debian machine. It also covers briefly SPF and other email authentication mechanisms.

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 Posted by at 9:32 am