Linux

Bash cheatsheet - Bash shortcuts you have to master

In this article I will present what are in my opinion the most useful and worth learning BASH shortcuts. Learning this bash cheatsheet can substantially make you more productive and work faster with the terminal. This is not intended to be a full list of all possible BASH shortcuts, and if you need it you better check the bash documentation. You can also download a printer-friendly BASH cheat sheet PDF that you can print and keep on your desk. You will find a link to it at the end of the article. Command Editing Shortcuts Shortcut Description Ctrl + a go to the start of… Read More »Bash cheatsheet - Bash shortcuts you have to master

C++ - Simple command line argument manager

Command-line argument management is tricky to get right especially when the number of options that we support and the number of their combination is big. For this kind of applications, there are already a number of very effective libraries and tools supporting the programming in such a scenario. One such library is Boost::program_options which I highly encourage you to use as is it awesome. But there are other cases where we need to quickly write a prototype or when the number of options and possible configuration is small where using Boost could be overkill. In such cases what we usually do is writing ad-hoc command-line… Read More »C++ - Simple command line argument manager

Dynamic Message of the Day - motd - Fedora Linux

HOW-TO: Dynamic Message of the day

This article is  about setting up a dynamic message of the day (possibly informative and fun) as header of each newly opened shell.

The final result will be something like the following:

header_shell

It mixes a fun message using fortune and cowsay which you can install using


sudo dnf install fortune-mod cowsay

utility and some informative info about the status of the system as:

  • System load
  • Ram and Swap available and used
  • Disk space
  • Ip address

 

The script file can be easily configured and extended to suits the your needs. Colors can also be easily customized.

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Distributed Hadoop installation - Fedora Linux

Distributed  Hadoop and HBase installation - Fedora Linux

In this post I will describe how to get started with the latest versions of hadoop and hbase describing all the step to obtain a working hadoop installation. The steps described here can be easily used to perform a working installation on a large cluster (even tough it can requires additional steps as shared filesystem for instance).

Prerequisites

 sudo dnf install openssh openssh-askpass openssh-clients openssh-server 

Don't forget to start the ssh service using the following command:

 sudo service sshd start 

Add a dedicated Hadoop/HBase User (optional but reccomended)

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CUDA - Julia Set example code - Fractals

This article present a CUDA parallel code for the generation of the famous Julia Set. Informally a point of the complex plane belongs to the set if given a function f(z) the serie does not tend to infinity. Different function and different initial condition give raise eventually to fractals. One of the most famous serie is   (the one that generated the video below). Some nice picture may be obtained with the following initial conditions: # dentrite fractal # douady's rabbit fractal # san marco fractal # siegel disk fractal # NEAT cauliflower thingy # galaxies # groovy # frost Here a video, showing a sequence of picture… Read More »CUDA - Julia Set example code - Fractals

Kernel Linux List - An Efficient Generic Linked List

Linux Kernel Linked List

Linux Kernel especially in the past years was plenty of different and replicated implementation of generic data structures such as linked lists, stacks and queues.  Kernel's developers decided to provide a unique set of API for using these kind of software machineries. We will briefly look in this article  at the list.h file (in the linux source tree under /usr/src/linux-headers-`uname -r`/include/) that provides macros and function for utilizing a doubly linked circular list. It is a very smart written piece of code that is worth to take a look at as it is  an opportunity  to improve  C programming skills and at the same time to see an "unconventional" implementation for a common data structure.

From canonical list to Linux kernel linked list

The canonical implementation of a C's linked list consists of a structure and two (for a doubly linked) recursive pointer fields to the structure itself. The links to the previous and subsequent element of the list.


struct point2DNode{
 int x,y;
 struct point2DNode* prev, next;
};

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Apple Xserve xeon Linux/Debian armed

Finally at my Departement we succesfully converted an  unsed  Apple xserve  cluster to a full functional Linux/Debian machine.

The cluster is make up of eleven node connected by Myrinet 10G low latency network and each node is a composed by a dual 4x cores Intel Xeon 2.8 Ghz Harpertown with 10Gb of DDR2 for a total of 88 cores. It is a quite old and small machine and hence was unused. We thought that  it could have been useful if well re-configured as an ad-hoc machine for small sized scientific computation session, as  developing and testing platform of parallel application or for training of undergraduate students that can experience directly with a real parallel machine. So we decided to cast a new light on it by configuring it as a Debian cluster (according to google just few people did it). 10949741_766948060061020_241789111_n

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