GNU/Linux, Open Source, Cloud Computing, DevOps and more...

How to enlarge the size of an EBS volume in AWS and extend an ext4 partition

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Logo AWS EBSWhen we completely fill up an ext4 filesystem mounted on a partition hosted in an EBS volume of Amazon Web Services and we can not do anything to free space because we do not want to lose any of the stored data, the only solution is to grow up the volume and extend the associated partition up to 100% of its capacity to obtain free space again.

DanielHow to enlarge the size of an EBS volume in AWS and extend an ext4 partition

Unlock Linux command line after pressing Ctrl+s in Bash

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Ctrl+SSince the key combination Control+s is widely used as a shortcut to save files in GUI applications such as text editors, image editors, web browsers, etc. sometimes you are betrayed by your subconscious when you are working from the Linux command line and you use that same key combination when you are for example editing a Vim document when trying to save it. Then you notice that no key answers, the shell is locked and you can no longer do anything else in it.  Even worse, you get a cold sweat because you can’t continue editing your document and you can’t save the changes.

DanielUnlock Linux command line after pressing Ctrl+s in Bash

Speed up your website with a SUPERLIGHT Facebook “Like” button

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facebook-like-buttonIt is often common to embed a Facebook “Like” button on your website so that on the one hand you show the number of followers of your Facebook page and on the other hand you invite the user to click on it to start following your page. However, this type of buttons tend to overload a website quite a lot because they consist of Javascript code that dynamically generates the button with the updated number of followers and the functionality needed to give a “Like”. This means that every time you load a page of your website you have to send 11 extra requests to the Facebook servers to download all the necessary elements. Given that these servers are currently located on the west coast of the United States and are not available through any CDN or similar service, depending on where the user is located, it is likely that each of these requests will have to cross half the globe to complete the download. All this causes your website to slow down unnecessarily and its loading speed is affected, which is quite negative in multiple aspects.

What if you could replace the button provided by Facebook with a single and simple image of the same button showing up-to-date number of followers of your Facebook page? It would be fantastic for website performance optimization or WPO, because it would only require a single additional request to the server, and it could be served and cached quickly from a CDN very close to the user’s geographic location. In this way you could ensure that the loading speed of your website would remain very high and without performance penalties.

How can this be achieved? It seems a win-win solution too good to be true… Well, it can be achieved in a much simpler way than you think thanks to the Imagemagick library and a simple Bash script. Read on…

DanielSpeed up your website with a SUPERLIGHT Facebook “Like” button

How to get a permanent token to access a Facebook page

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Through the following instructions you can easily get a permanent access_token to automatically connect your applications to a Facebook page and be able to obtain for example your number of followers periodically, get new likes or comments in real time, publish new entries in the timeline, or any of the possibilities offered by the Facebook Pages API.

DanielHow to get a permanent token to access a Facebook page

Web application for live onsite and online car auctions

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This was a very interesting project related to the automotive business in which I led a technical team of 4 people in the design and development of a complete software intended for conducting live car auctions both onsite and online in a large industrial building especially conditioned for this kind of events. Unfortunately, despite the beauty of the project and being a startup with great potential and highly talented team of almost 20 people, the application could not finally be used in a real scenario because the company wound up before it could actually start due to various commercial and management issues.

However, at the technical level the application was implemented and deployed completely, fulfilling very satisfactorily the requirements and objectives initially set out. Our application was mainly inspired by the BCA and Autorola car auction softwares, and also others like CarsOnTheWeb, ManheimEurocarBidSubastacarSubasto mi Coche, etc. I humbly believe that we managed to improve them in several ways.

DanielWeb application for live onsite and online car auctions

What is the true meaning of system average load and CPU utilization in Linux?

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The CPU average load value is a very important metric to understand the behavior of a Linux system, and especially its current and recent past status. Many times there is confusion between this term and percentage of CPU usage, but differences are important. In this article I will try to explain the true meaning of both and how to tell if a Linux box is overloaded or underutilized.

DanielWhat is the true meaning of system average load and CPU utilization in Linux?

The importance of properly partitioning a disk in Linux

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Linux disk partitionI am a strong supporter of simplicity and the principle that less is more, but as far as security and performance of information systems is concerned, we must be able to strike a balance between keeping things simple and exposing ourselves as little as possible to potential threats while trying to obtain the maximum performance of all system elements involved.

It is a common practice that the various distributions of Linux, and even the images used to launch Linux virtual server instances as in the case of AWS AMI’s, implement by default an extremely simple partitioning scheme consisting in a single partition that covers the entire disk. It is in this only partition where the root filesystem (/) is mounted and in which all the directories that configure the file hierarchy of a Linux operating system are placed.

But one of the features of Linux is precisely that it allows you to be highly flexible in placing each of these directories on different partitions or on different disks if necessary.

DanielThe importance of properly partitioning a disk in Linux

Differences between physical CPU vs logical CPU vs Core vs Thread vs Socket

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When we try to know a computer’s architecture and performance at CPU level using Linux commands like nproc or lscpu, we often find out that we are not able to properly interpret their results because we confuse terms such as physical CPU, logical CPU, virtual CPU, core, thread, socket, etc. If we add concepts like HyperThreading (not to be confused with multithreading), we are in a situation where we can not be sure how many cores our box has, we don’t understand why commands like htop indicate that we have 8 cpus when we thought we had bought a single quad-core processor, etc. In short, it’s a mess.

DanielDifferences between physical CPU vs logical CPU vs Core vs Thread vs Socket