Linux User & Developer -julkaisun No. 163 -irtonumeron sisällysluettelo

This issue » Set up a rock-solid network from scratch » Hack your old Xbox controller with a Pi Zero » Secure your website with Let’s Encrypt » Run a Raspberry Pi 2 Docker Swarm Welcome to the latest issue of Linux User & Developer, the UK and America’s favourite Linux and open source magazine. Setting up a complex network, whether for your home or the office, is no mean task, but it is far easier than you might realise. And the payoff? A wealth of functionality, directly configured to suit your needs: perfect port forwarding and proxy servers, automatic backups, remote access, file and media servers, file sharing, monitoring tools – all of it put together by you and easily managed from a single control node. Turn to page…

1 Transaction hooks For the first time in version 5.0.0, the pacman package manager can now run hooks either before or after transactions. Hooks can be specified using the alpm hook file format, with the user describing a single action that is to be run based on one or more triggers. 2 .files support With this latest release, pacman gains the ability to sync and read .files databases using the -Fy switch, as well as the ability to perform basic searches for files contained in sync repositories using -Fs and -Fo. 3 Corruption handling If pacman 5.0.0 encounters a corrupt database, it will automatically update from the remote copy even if the remote is the same version. The new version also gains improved signal handling and lock file removal. 4…

The Linux Foundation has announced its latest collaborative effort: Fast Data ( FD.io ), an open source project which seeks to provide a high-speed input-output services framework for next-generation network and storage software. Initial contributions to FD.io include vector packet processing (VPP) capabilities in a fully-functional vSwitch/vRouter setup based around the Data Plan Development Kit (DPDK). This, the Foundation claims, offers high-performance hardware-independent IO, along with a full build, tooling, debug, and development environment, along with an OpenDaylight management agent and Honeycomb netconf/yang agent. “The adoption of open source software has transformed the networking industry by reducing technology fragmentation and increasing user adoption,” claimed Jim Zemlin, executive director of TLF, at the launch. “The FD.io project addresses a critical area needed for flexible and scalable IO services to…

Keybase, the public-key social-networking-powered cryptography service created by OkCupid co-founders Max Krohn and Chris Coyne, has a new string to its bow: an early implementation of a cloud-backed, fully-trusted shared file system. Dubbed the Keybase File System, or KBFS, the new software allows Keybase users to automatically store signed files for public viewing or encrypted private files which can be accessed by any of their Keybase-linked devices. These folders can also be created for multiple users: two or more users can share a dynamically-created public or private folder, for example, with files being signed and encrypted appropriately. “Our goal: smack-dab in the middle of a public Reddit or HackerNews or Twitter conversation, you should be able to say ‘Hey, I threw those gifs/libraries/whatever in our encrypted Keybase folder’ without ever…

“So, tell us a little bit about yourself. Well, I just turned 14 about four months ago. I’ve been speaking at conferences since I was about 11 years old… [laughs] I’ve always been into computers, probably since I was about three years old. I started getting into coding when I was nine – that was when I wrote my first website. So you grew up surrounded by it? My dad was an IT consultant, and he always did his projects in his back office. I actually ended up finding his work book, and so that’s how I ended up getting into it. I wasn’t actually sure about it until I read the book, and then I started getting support and encouragement from my dad. I actually had to find it…

“Linus Torvalds announced the first few release candidate (RC) kernels for what will become Linux 4.5. In his announcement, he noted that 4.5 was shaping up to be “a fairly normal release – neither unusually big or unusually small”. One element he specified in the 4.5-rc1 announcement was the tremendous work done over the past five years by the 32-bit ARM Linux community towards “multi-platform” kernel support that has culminated in 4.5. Linus giving the ARM community praise is a far cry from his outbursts just a few years ago about the state of platform support. The 4.5 kernel includes many fixes, though not wholesale subsystem changes of the kind we have sometimes seen in previous cycles. Instead, there are incremental features, including support for the MADV_ FREE application memory…

There will be times when you will need to access your server from the internet but that server is not directly connected to the internet. In these cases, we can use a technique called port forwarding. Port forwarding allows you to forward network packets from your router’s IP and port to one of the LAN’s IPs and ports. For example, let’s assume your router’s internet IP is 215.58.193.110 and you are running a web server on one of the computers on a LAN with the IP address 192.168.1.7 at port 80. When using port forwarding, if somebody on the internet is accessing http://215.58.193.110:80, the router will automatically send the traffic to http://192.168.1.7:80. To enable port forwarding, you can go to your ISP’s router config page and look for the port…

If you have a large number of devices on your network, a proxy server can help you save bandwidth by caching the regularly accessed content directly on the server. This is not the only use of proxy servers; proxy servers also allow you to control and monitor the internet traffic on your network. Squid is a popular proxy server that provides all these features. To install it: To configure squid, edit /etc/squid3/squid.conf. Squid runs on port 3128 by default. You can change it by editing: The following lines will enable the access for the network 192.168.1.0: On client devices, you open the proxy settings and use http://<ServerIP Address>:3128 as the proxy server.…

Rsync is an incremental network and remote file copy tool. You can use rsync to keep folders or files in sync with each other between different directories or system. For a given folder, rsync only transfers files which are not already transferred. For files, it checks which part of files have been changed and is able to transfer just the modified part. Due to these features, rsync is a very popular choice of backup. To transfer files on the same computer you can use the following command: This command is similar to cp but with key differences: in this transfer, the -P option tells rsync to show progress and keep partial files. So if for some reason you were to cancel the transfer in the middle, this will be automatically…

Ajenti provides a consistent way to manage Linux systems across its supported distros, and boasts an easy-to-use dashboard that is customisable. Head to ajenti.org and choose your distro base, then follow the provided instructions to install the software. After installing it, start Ajenti with this: Ajenti is available at https://<ServerIP>:8000, the default username is root and the default password is admin. You will obviously need to change this as soon as possible – head to Password from the left navigation bar now and change your password to something much stronger. While installing, Ajenti generates a self-signed certificate which is okay for normal installation but not good for production. You can change the certificate by providing a pem file at Configure > General > SSL > Path to certificate. If you…

A logging facility is like a category used for logging information. The following line of the /etc/rsyslog.conf configuration file defines that all logging information for the local7 facility will be stored in a file called /var/log/cisco.log file: The value of the logging facility part can be any one of the following: auth, authpriv, cron, daemon, kern, lpr, mail, mark, news, syslog, user, UUCP, local0, local1, local2, local3, local4, local5, local6 and local7. The next line of code defines the logging facility in logging.c as well as the name of the program that will appear on the relevant log entries:…

Resources Atom atom.io Atom Flight Manual atom.io/docs For coders, writers and sysadmins – essentially anyone who spends a lot of their screen time entering words through a keyboard – the text editor is something of a sacred tool. Keyboard shortcuts are embedded in muscle memory, and the peculiarities of the environment – whether constant modal shifting in vi(m), or Escape-Meta-Alt-Control-Shifting in Emacs – second nature. Moving to another editor, even trying one out in a more than desultory fashion, is a serious undertaking, requiring real motivation. Big news, then, that in its short life (the main components were open-sourced less than two years ago, and version 1.0 reached just last summer), GitHub’s Atom editor has pulled in hundreds of thousands of regular users. How has it done it? Built from…

Resources Let’s Encrypt letsencrypt.org Whether you manage your own Linux web server or you’re in the process of setting one up (for live use or for testing and development), there is a strong possibility that you will need to configure HTTPS and acquire SSL certificates. The “secure sauce” of online shopping, banking and data management is secure encryption, but it has traditionally been characterised with a clunky, outdated set of procedures. Validation emails, configuration editing and avoiding the dreaded expired certificate issue – a problem that can break secure websites – all inspire nothing but trepidation. Given the weaknesses in SSL certification – highlighted in 2015 with the Superfish malware scandal, and the problems maintaining OpenSSL – it is becoming increasingly important to ensure that certificates are genuine, and trusted.…

For a production installation, users should consider one of the Hadoop cluster management tools like Cloudera Manager or Apache Ambari as they provide well-tested wizards for getting a working cluster in a short amount of time. Extra features like unified monitoring, log searches and rolling upgrades are also present so that you can upgrade the cluster without experiencing downtime. Also, the balancers program redistributes the data blocks by moving them from over-utilised DataNodes to underutilised one. RPM and Debian packages are available from the Apache Bigtop projects and they provide a consistent file system layout.…

The Raspberry Pi Zero is tiny, ridiculously tiny. It’s a wonderful, impressive piece of tech, but we can’t help wondering – because we’re terribly serious adults, honestly – where can we stuff the Zero for maximum fun? It’s small enough to be hidden in a variety of household objects in order to enhance their capabilities. Whatever you can find to fit it in, you can turn into some kind of smart machine. Okay, wiring it in to your vacuum cleaner in the hope of making an ersatz Roomba is probably a little tricky – but there are all sorts of electronic gadgets lying around your home which can be brought back to life with a little bit of effort. Take old game controllers. If you’re anything like us you’ve probably…

“In a previous article, we looked at how you can capture images using a camera and a Raspberry Pi. This let you include image capture functionality within your own Python program, but there is so much more you can do once you add vision to your code. This month, we will look at how you can add motion detection to your Python program. This kind of advanced image processing is extremely difficult to do, so we will definitely be building on the hard work of others. Specifically, we will be using the excellent OpenCV Python package. This package is constantly being improved, with more functionality being added with every update. The first thing you will need to do is install the various Python packages that you will need to talk…

You may remember or have even played the classic Minesweeper PC game that originally dates back to the 60s. Over the years it has been bundled with most operating systems, appeared on mobile phones, and even featured as a mini-game variation on Super Mario Bros. This project will walk you through how to create a simple version in Minecraft:it’sMinecraftMinesweeper! You will code a program that sets out an arena of blocks and turns one of these blocks into a mine. To play the game, guide your player around the board. Each time you stand on a block you turn it to gold and collect points, but watch out for the mine as it will end the game and cover you in lava! 01 Update and install To update your Raspberry…

Yes, there are a lot of media players around, and collection managers, too – there are even plenty of apps that claim to do both jobs well, but they all have different niggles so we’re always prepared to take a look at another one. Lollypop is quite pared down, handling just locally stored songs and a Last.FM account, but aiming to do these simple things well. Lollypop is edging towards a 1.0 release and advertises itself as a GNOME music player, and it does look good on GNOME – but we ran it on LXDE as well and just enjoyed the music. Well, not just music; we tried its sorting abilities on a week of BBC radio programmes downloaded with the get-iplayer script. This showed up one disadvantage common to…

“Simple, flexible and cost-effective cloud infrastructure services with high performance, availability and scalability” About us ElasticHosts offers simple, flexible and cost-effective cloud infrastructure services with high performance, availability and scalability for businesses worldwide. ElasticHosts’ global team of engineers provides excellent support, around the clock by phone, email, and ticketing system. The company is true to its name; ElasticHosts servers can be resized at will, run any OS, and are managed through a user-friendly web control panel with instant VNC access. ElasticHosts offers ten data centre locations around the world, including the UK and Europe. After seven years of helping development shops, systems integrators and tech startups run their businesses more efficiently, ElasticHosts has developed an excellent reputation. What we offer • Cloud hosting – reliable cloud servers with any specification…

YOUR BONUS RESOURCES ON FILESILO THIS ISSUE, FREE AND EXCLUSIVE FOR LINUX USER & DEVELOPER READERS,YOU’LL FIND THESE GREAT RESOURCES… » Four latest distros, including Tails 2.0, plus the new Raspbian featuring an experimental OpenGL driver. » 20 excellent FOSS packages, including everything you’ll need for the network feature, plus a few extras. » Watch The Linux Foundation, Red Hat and Raspberry Pi video guides, tutorials and webinars. » Code and assets for this issue’s tutorials, including everything you need for the Raspberry Pi feature. LENGTH OF VIDEO TUTORIALS: 20 HOURS www.filesilo.co.uk/linuxuser…

A rapidly growing library Updated continually with cool resources Lets you keep your downloads organised Browse and access your content from anywhere No more torn disc pages to ruin your magazines No more broken discs Print subscribers get all the content Digital magazine owners get all the content too! Each issue’s content is free with your magazine Secure online access to your free resources This is the new FileSilo site that replaces your disc. You’ll find it by visiting the link on the following page. The first time you use FileSilo you’ll need to register. After that, you can use the email address and password you provided to log in. The most popular downloads are shown in this carousel, so see what your fellow readers are enjoying! If you’re looking…

01 Follow the instructions on-screen to create an account with our secure FileSilo system, then log in and unlock the issue by answering a simple question about the magazine. You can access the content for free with your issue. 02 If you’re a print subscriber, you can easily unlock all the content by entering your unique Web ID. Your Web ID is the eight-digit alphanumeric code printed above your address details on the mailing label of your subscription copies. It can also be found on your renewal letters. 03 You can access FileSilo on any desktop, tablet or smartphone device using any popular browser (such as Firefox, Chrome or Safari). However, we recommend that you use a desktop to download content, as you may not be able to download files…

“Corporate hostility to copyleft and the GPL is nothing new, but it’s worth remembering how such companies have benefitted from the GPL” “The GPL has never been the flavour of the month in the corporate world, where copyrights and patents are seen both as revenue streams and as instruments to inhibit competition, and the GPL and copyleft are often dismissed as mad, bad and dangerous to know. Companies take advantage of what free software can bring; few make an active contribution to the enforcement of free software licences. GPL enforcement is left to community efforts like Software Freedom Conservancy (SFC), which depends on voluntary contributions. Funding of GPL conservancy has re-emerged as an issue because of the suggestion by Karen Sandler, SFC’s executive director, that “over the past year, and…

The Linux Mint project – consistently the most popular Linux distribution on trackers such as distrowatch.com  – has suffered an attack that compromised its website and left infected ISO images on its download mirrors. The attack was acknowledged by the Linux Mint team in the early hours of Sunday 21 February, who stated that “hackers made a modified Linux Mint ISO, with a backdoor in it, and managed to hack our website to point to it.” Gaining access via a PHP script in the Linux Mint website server’s WordPress installation, the hackers redirected visitors to their own server, which hosted the compromised version of a 64-bit Linux Mint 17.3 Cinnamon ISO. The Linux Mint team advises that anyone who downloaded the 64-bit Cinnamon edition on Saturday 20 February…

The Docker project has confirmed that it is moving its official images from Canonical’s Ubuntu Linux to Alpine Linux, and that it has hired distribution founder Natanael Copa to assist with the transition. “Today most people who use Docker build containers with unnecessary distro bits in them,” admitted Solomon Hykes in a post to Hacker News. “But before Docker, 99% of them didn’t build containers at all, and struggled with non-repeatable deployments and dependency hell. Even better, now all these people use a standardised Dockerfile which can be changed and improved over time – for example to move away from a heavyweight distro like Fedora or Ubuntu, to something like Alpine or even more minimalistic.” That move, made with a view to reducing the size of Docker images, is currently…

Keila Banks has been giving talks at Linux and open source conferences for years, but her ‘Undefinable Me’ presentation at OSCON 2015 brought her into the wider public eye. Available to view on Prezi (prezi.com/vcxglzmkv_xy/undefinable-me), her excellent keynote is an investigation and celebration of identity in the community. Banks begins discussing her appearance with the audience, asking them to consider how they would define her, and then challenges this definition again and again by revealing more about herself, her passions and her skills. By the end of the presentation, it’s impossible to not be impressed by her accomplishments, passion and drive. Do yourself a favour and watch it: youtube.com/ watch?v=xkTcSoQ-q5Q.…

With so many different devices filling our living rooms and our desks at work, it’s more important than ever to know how to get them all talking to each other. It makes sense, for example, to have your phone in touch with your home’s music library, so you can easily play your favourite album without having to switch to your desktop. And it makes sense to have one computer in your office in charge of backing up all the others on a regular basis. Sometimes you need to be able to fine-tune the permissions that various connected devices have on your network. All this and more is possible by simply building a network from scratch to include these features. Over the next few pages we’re going to take you through…

One of the key bottlenecks in your internet speed is the DNS server. Any time you load a web page it goes to the DNS server for an IP address. If your DNS server takes too long to respond to the request it makes the complete network slow down. Public DNS services like Google DNS and OpenDNS provide fast DNS servers that can accelerate your complete internet experience, but before you switch your DNS you should benchmark your ISP’s DNS using namebench to see if you will get any benefits.…

Sometimes you may need to troubleshoot a misbehaving client on the network or want to optimise the network. Here we will talk about some tools that help with various aspects of the network: ifconfig: Ifconfig can be used to configure and monitor the network interfaces. Without any arguments, ifconfig will list the details of all the active interfaces. route: The route command will show you the kernel routing table of the system: In the above command output it says that traffic with destination network 192.168.1.0 should go via eth0 interface without using any gateway. Similarly, any destination with 192.168.20.0 should go via vpn_azureasia interface. Default gateways are used when the any other destination is being used. traceroute: This command allows you to find out the route to a particular host…

SSH (Secure Shell) is a very common way to log in to a system remotely. OpenSSH is the most popular SSH implementation that is available across all the popular platforms: Linux, Windows, Android, iOS, etc. To install the OpenSSH server, use: Once installed, openssh-server is ready for action without further configuration. Log in from a remote machine using: The username should already exist on the server. By default, OpenSSH is configured for password authentication. A far more secure way to log in is to use public-key authentication. On the remote machine, generate the public/private key pair: Use the default options. You will have two files in the <YourHomeDirectory>/.ssh folder: id_rsa and id_rsa.pub . Id_rsa is your private key – do not share this with anybody. Copy the content of id_rsa.pub…

Media file support varies when you take account of smart TVs, smartphones, tablets and game console. An mkv file that plays fine on your PC may not be supported everywhere. In order to get around this, Plex Media server implements a technique called On the Fly Media Transcoding. Based on the Plex client request, Plex Media Server will do transcoding of the requested file into something that clients report as playable and stream it. This process is CPU intensive so make sure to use a multicore CPU if you are going to use this feature.…

The existing Go library, as implemented using packages, allows you to create server processes in a surprisingly easy way. The provided server program server.go shows how you can send logging information using Go by using the syslog Go package, which provides a simple interface to the system log service. Take a look at the Go code of server. go, which produces output of the following form: Unfortunately, you do need to execute a Go server using the workaround nohup command, which is a little outdated.…

Atom isn’t the only cross-platform text editor based on web technologies that’s calling for consideration. Light Table is also based upon Electron (formerly Atom Shell) but is written in ClojureScript. Billing itself as “the next generation code editor”, it has similar abilities to Atom, albeit with a smaller community and developer base, but feels faster. The Light Table developers are also working on the ambitious Eve: “a set of tools to help us think.” (http://lighttable.com)…

Resources Hadoop bit.ly/20m1Z3h With the advent of new technology – and a growing number of social networking sites, scientific research projects and new business models – available data is growing rapidly. This data is mined to churn out the relevant information: DNA data is studied to analyse hereditary diseases; data from shopping sites is used to find the buying trends of customers and suggest new products to them; weather station reports are used for weather forecasting, and so on. Now, since this data is mostly unstructured and mammoth in size, it’s hard for a traditional database to store and manipulate it. This led to the emergence of an open source technology called Hadoop. Hadoop stores the data across the several nodes in a cluster in HDFS (Hadoop Distributed File System)…

Resources Text editor GCC compiler Python compiler Perl interpreter Here we are going to go through the structure of binary trees as it is the most frequently used kind of tree. This tutorial will present the necessary knowledge and code that you need to know in order to begin using the tree data structure and help you understand how a tree works and why it is so fast. The presented code will be mostly written in C but you are also going to see examples in both Perl and Python. The Go and Rust methods of creating binary trees will also be discussed. The main benefit of using a tree is that you can find out if an element is present or not in a very short time. Trees are…

In the main article, we have been using the Raspberry Pi module that plugs into the IO bus of the Pi. But what if you don’t have easy access to one of these? Almost everyone has an old webcam sitting around the house somewhere, and the Raspberry Pi has a perfectly useful USB port. The image quality and frame per second count is not as good as what you can get with the actual Pi Module. The key is getting the image data off the camera in the format that the OpenCV image analysis functions is expecting. The VideoCapture() function can not only take a video file name to read in, but can also take device IDs for cameras attached to the Raspberry Pi. Assuming that you only have one…

Tabview is a command line viewer for CSV and tabular data, written in Python, which uses the familiar ncurses library for a spreadsheet-like display. Installation is a simple matter of: … with other options available for non-Pip users. That said, you really should embrace Python’s Pip installer, which has recently been updated to 8.0.0. If you wish to use tabview as a pager in MySQL, edit /etc/my.cnf to include: It can also be called as a module from an interactive Python3 session, for a useful tabular look at any data structure you want to check. But it is as a command line tool that tabview could have its widest audience, both for those who don’t wish to open up an office suite just to look at a CSV file, and…

Top 10 This month Android-x86 has increased in popularity dramatically this month, to the detriment of Mageia and Deepin, which slip off the top ten Highlights Android-x86 Android-x86 4.4-r5 brings with it fixes for a number of issues. The biggest changes include compatibility with official Microsoft Surface devices and full support for booting on legacy BIOS and UEFI machines. RebeccaBlackOS The Wayland demonstration distribution RebeccaBlackOS now includes a switch to Debian Testing for packages, compatibility with legacy and UEFI systems, and the ability to load a KDE Plasma session on top of Wayland. Scientific Linux The 7.2 release of Red Hat-based Scientific Linux includes an installer capable of quickly locating the fastest local network mirror and initial support for Scientific Linux Contexts. Latest distros available: filesilo.co.uk…

“The only thing you should definitely make sure of is that the value of the divisor is not zero, because you cannot divide a number by zero” “Manually implementing integer division is not a particularly difficult problem per se but there are many details that need to be taken care of. In a division operation you have two numbers: the dividend and the divisor. The result of a division is one number, called the quotient. If the division is not perfect, you might have a remainder. So you have the following equation when dividing natural numbers: This can also be written equivalently as: We must decide whether or not an algorithm will support negative integers. This is not a big issue but it is something that you should decide before…

Have you been inspired to attend your first conference or join a group? Well, a few interesting events are just around the corner. This year, the Girls in Tech Catalyst Conference is being held in Phoenix, Arizona, on 17-19 April (phoenix.catalyst.girlsintech.org). With a focus on entrepreneurship and education, the event is packed with speakers and promises some excellent workshops and discussions. O’Reilly’s Open Source Convention, OSCON, will be held on 18-19 May in Austin, Texas, and the event typically takes in a wide spectrum of open source technologies and has been known for groundbreaking project announcements. The PyLadies community will be down at PyCon 2016 to run a charity auction, so if you’d like to get involved with them then get to Portland, Oregon, for 28 May – 5 June.…

VNC is a popular desktop sharing system implemented using the RFB protocol so you can share your current desktop over the network. VNC can be used to provide multiple users on the server with an isolated desktop environment simultaneously. This means they all can run their own apps in their own desktop environments. To install TightVNC: We are also installing a lightweight desktop environment called Xfce, which we will use to boot the GUI session for remote users. Autocutsel is service used in order to add copy-paste support between host and the client. We will need to configure the desktop environment, too. Create ~/.vnc/xstartup and add: Make this file executable with a quick sudo chmod +x xstartup. For each user, a service file needs to be created, and this will…

Dropbox is very popular with both individuals and businesses for its simplistic approach of sharing and syncing files over the internet between multiple devices. Seafile is an open source implementation of the same concept that allows you to keep files on your own server. It runs on Linux, Mac and Windows. On mobiles it runs on Android and iOS via free apps. One of the key features of Seafile is built-in file encryption. This feature allows you to encrypt your library using a password. This way even server admins or snoopers on the server will have no access to your files. To install Seafile, install the supporting packages: Download the server for generic Linux from https://www.seafile.com/en/download. After extracting the folder, run setup-seafile.sh to run the guided setup program. This will…

Resources Text editor GCC compiler Go compiler Perl interpreter A server process is a special kind of process with unique characteristics. The most common feature of server processes is that they run in the background, which means that they run without having a controlling terminal associated with them. As usual, most of the presented code will be written in C. However, you are also going to see examples in Perl and Go because these languages allow you to create reliable server processes with the help of their existing modules and libraries. Please remember that if you are developing a server for a production system, the server process should behave perfectly; therefore, we do not recommend creating a server process that you plan to put on a production environment without proper…

Check out the source code of the supplied server.pl, which uses the TCP protocol with port number 12345 to communicate with the rest of the world. Once again, you should use the nohup utility in order to make server.pl keep running even after you log out from your Linux machine. You should use the Sys::Syslog Perl package to be able to send logging information. The logging information from server.pl has the following format: Bear in mind that as Perl is an interpreted programming language, everyone will be able to look at the source code of your server process.…

Resources MonoGame monogame.net The past few tutorials in this series have promoted a solid understanding of models, the rendering pipeline and the role of shaders. Essentially, a shader is a program that handles part of the projection process which transforms three-dimensional objects into two-dimensional scenes fit for display on a PC screen. Sadly, the creation of realistic models requires the deployment of a large amount of geometric detail. If colouring is to be achieved, the amount of vertices needed grows sky-high – at some point, even the most high-performing GPU will declare itself beaten. Textures provide a nice workaround. Think of them as skins that wrap around the vertices: instead of rendering an entire part of a model in one colour, the colour values used are obtained from the texture…

The data is copied from various resources and kept on HDFS. Hadoop dfs –put <<local_ filesystem_path>> << HDFS_filesystem_ path>> is the command to put the file on HDFS. Please note that Hadoop does not let you put the files in an already present directory; every time you add a file, you have to create a new folder or else it will give the exception “Output directory already exists”. Make a directory using the command hadoop dfs –mkdir /Data and then the data is put on HDFS by executing hadoop dfs –put /usr/UN.txt /Data. The data can also be seen in the browser by browsing the specified file.…

The tree.pl Perl script shows how to implement a binary tree in Perl, as well as how to traverse it and print its contents on-screen. The good thing with Perl, and the main reason for using Perl, is that it has modules that can do almost anything you want; there exist various modules that can generate trees without you having to implement anything. Find tree.pl in your resources pack and run the script to see the beautiful output that is produced by Perl. What is wrong with tree.pl is that you will have to manually generate the tree structure before using it. The most important code of tree.pl is the following: The first command creates the tree and the second command draws it using ASCII characters. Should you wish to…

Zheng Wang has an academic background in electrical engineering and has put what he has learned into action with his Pi car project. Like it? Zheng has documented the entire process over on his blog at bit. ly/22Zh5uq. For those who want to replicate it for themselves, Zheng has also outlined the equations needed to get the object detection working correctly. Further reading David Singleton was where Zheng took his inspiration from, and we recommend you go check out his guide on how he built a neural network RC car at blog. davidsingleton.org/nnrccar. The process is a little different from Zheng’s, and it’s certainly an interesting read. Components list Raspberry Pi B+ Arduino Camera module HC-SR04 ultrasonic sensor OpenCV Camera The camera module is the focal point for object detection. Input data…

Arch Linux runs on a rolling-release model, which means system upgrades are incremental and packages are bleeding edge What you’ll need • Github repository github.com/alexellis/docker-arm • Arch Linux for ARM archlinuxarm.org Docker is a framework and toolchain used to configure, build and deploy containers on Linux. Containers provide a means to package up an application and all its dependencies into a single unit. This makes them easy to share and ship anywhere, giving a lightweight and repeatable environment. Each application runs in its own isolated space sharing the host’s kernel and resources, in contrast to a virtual machine which needs to ship with a full operating system. A Docker container can be started or stopped within a second, and can scale to large numbers while having minimum overhead on the…

Unless you rely entirely on the command line to manage your files and navigate around your crowded hard drive, the file manager is a crucial part of day-to-day computer use, yet many stick with their distro’s default manager despite multiple annoyances. Trying out a new file manager to see if it’s a better fit for you can be well worth the effort, and SpaceFM – a fork of the original, lighter weight PCManFM – has plenty to offer. SpaceFM is usable as the kind of file browser you’re used to, but you can open extra panes (up to four in total) in the window – each with as many tabs as you like – with additional side panes for a tree view of directory structures or bookmarks; you can further…