Linux User & Developer的No. 165目录

This issue » Behind the scenes with Ubuntu 16.04 » Hands-on with the BBC micro:bit » Make a Raspberry Pi sound system » Recover lost data from a hard drive Welcome to the latest issue of Linux User & Developer, the UK and America’s favourite Linux and open source magazine. The latest release of an OS is always an exciting time, and this issue we go behind the scenes with Canonical to discover just what’s in store in the latest long-term support release of Ubuntu – check it out on p18. But knowing what’s going on in Ubuntu is no fun unless you get to play with it too, so that’s exactly what we’ve included on this issue’s free disc. Load it up and live boot into the 32-bit or…

1 GIMP Image manipulation is a big deal when it comes to designing for the web, so a program that’s as powerful as GIMP is a must-have. The ever-changing suite of features rival many of what Photoshop offers, but it still keeps its simplicity intact for those experimenting with this sort of program for the very first time. 2 FileZilla As far as FTP software goes, nothing compares to what FileZilla manages to do. There are two downloads involved, with one the client and the other its associated server. Together they form a formidable team to get your content online in a matter of minutes. 3 KompoZer For on-the-spot web editing, choices are plentiful, but the simplicity of KompoZer is the primary reason it has gained such a following. As…

Ubuntu developer Canonical has extended its partnership with Nexenta to continue to provide a new take on software-defined storage solutions. Nexenta is one of the leading names in the development of open-source storage solutions, but this new agreement will be heavily focused on Canonical’s Ubuntu platform. Integrating Nexenta’s storage solutions with the Canonical’s Ubuntu OpenStack software is a game changer, enabling Ubuntu users to manage, reply and scale apps in the cloud – and all without being tied to their desktop. While similar options are readily available on the market, there are numerous complaints with nearly all of them. With the correct development and integration into the Ubuntu platform, there’s a big chance the finished product could become a must-have piece of software. Mark Shuttleworth, founder of Canonical, has said…

Microsoft has finally released an update for its popular developer suite, Visual Studio, which enables users to now write C++ code for Linux desktops and servers. There are several restrictions in place, however, and in its current state the extension will only support building remote servers on Linux machines. All of openssl-serve, gdb and gdbserver will need to be installed prior to use, but thankfully there are no limitations on the distribution it can be used on. To cater for different audiences and requirements, the extension comes with three different templates: Console Application, Blink for IoT and Empty. Each allows for different forms of code development, with Empty being the preferred choice for those already fluent in C++. Microsoft has been on a Linux-releasing binge as of late, with its…

For those who are eager to develop their own IoTenabled devices, finding the right hardware to use can be a surprisingly difficult task. While there’s a multitude of options out there, a great entry point is to use the Raspberry Pi. It’s a cost-effective and relatively simple solution to the issue, with enough resources readily available to help you find your way with it. Projects are vast and varied and the open nature of the Raspberry Pi lends itself well to any number of IoT projects you may have concocted. For many, their knowledge of IoT will go towards to the idea of the smart home, and the Raspberry Pi can play an integral part in developing your own smart home system. One of the easiest IoT projects to get…

“ OrangeFS lands in Linux 4.6 as a built-in Linux kernel filesystem, and represents the culmination of years of effort ” “ Linus Torvalds announced the closing of the Linux kernel development merge window (the period of time during which disruptive changes are allowed in any two-month kernel release cycle) for what will become Linux 4.6. In his mail, which provided links to the first Release Candidate (4.6-rc1), Linus noted that this had been “one of the bigger merge windows in a while”, leading to his closing the development cycle a day earlier than normal in order to avoid someone trying to sneak in a last-minute feature or ten. He also noted that 4.6 had been “pretty pain-free”, and in particular that the ARM community had really done an excellent…

Resources A text editor such as Emacs or vi The gcc compiler The Perl compiler The Go compiler The Python compiler IPC allows processes to talk to each other. The history of IPC on UNIX started with pipes, which is the oldest method of IPC, and now we mostly use the internet, which is another form of IPC. Between pipes and the internet exist FIFOs, shared memory and UNIX domain sockets, which are also going to be covered in this tutorial. Introduction to IPC The most popular IPC technique used in UNIX systems is the pipe, which existed since the early versions of UNIX. As a simple example, the following command uses a pipe behind the scenes: $ ls -l | wc. This creates a separate process for each command…

“ Cloning a GNU/Linux computer can be easily achieved by copying its entire slash partition ” Resources VirtualBox https://www.virtualbox.org/ SystemRescueCD https://www.system-rescue-cd. org/SystemRescueCd_Homepage GHOST http://www.openwall.com/lists/osssecurity/2015/01/27/9 rsync common flags http://www.evbackup.com/support-commonlyused-rsync-arguments/ From time to time, a bug can affect a critical layer of the operating system, like the GNU libc6 (as in CVE-2015-0235 and CVE-2015-7547), or the GNU/Linux Kernel itself (as in CVE-2016-0728). Patching such bugs tends to be straightforward on modern GNU/Linux distros, but sometimes you are not so lucky: old systems could still be running on your network. The only way to fix their security vulnerabilities is by hand, with all the risks this task entails: kernel panic during the booting process, segmentation faults that occur out of the blue, etc. In such cases, having a cloned system will allow you…

What you’ll need • A Raspberry Pi for each room you would like to play music in (one of these can act as a server or a sever can be separate) • Ideally a USB sound card for each Pi (a Behringer UCA-202 is a great option) • Speaker amplifier and speakers to plug the Pi into • A wired or wireless network • A USB Wi-Fi adapter for each Pi you want to be wireless (an Edimax EW-7811UN works out of the box) In this article we are going to use Logitech’s Squeezebox Media Server and the squeezelite client to create a multi-room audio system. The media server can stream audio to each squeezelite client and also synchronise the playback between multiple clients if desired. Logitech open-sourced the Squeezebox…

You can even identify whether there is a smile in the image Why Python? It’s the official language of the Raspberry Pi. Read the docs at python.org/doc “ In a previous piece, we looked at how you could use your Raspberry Pi and some Python code to look at a scene and figure out whether there was any motion there. This month, we will take it one step further and see if we can get our Raspberry Pis to actually recognise faces. We’ll assume here that you are either using the camera module for the Raspberry Pi, or a USB web cam. In either case, you have a stream of images being handed to your code, ready to be processed. Again, as in previous articles, we will be using the…

What you’ll need • Wireshark (www.wireshark.org) • Raspberry Pi 2 • SenseHAT You will probably have played Rock, Paper, Scissors in real life. The issue with this version is that there are only three possible outcomes other than a tie. Sam Kass and Karen Bryla invented an alternative version which adds “Spock” and “lizard”. “Spock” is signified with the Star Trek Vulcan hand sign, while “lizard” is shown by forming the hand into a mouth. Spock smashes scissors and vaporises rock; he is poisoned by lizard and is disproved by paper. Lizard poisons Spock and eats paper; it is crushed by rock and decapitated by scissors. This tutorial walks you through creating your own SenseHAT version of the game. 01 How RPSLS works with the Sense HAT When you complete…

Nmap is a popular security scanner that can be used defensively or offensively, the choice is with the user. Nmap’s detection of vulnerabilities in networks is what makes it so useful for both black and white hat hackers – and in your efforts to keep out undesired intrusion into your network. The latest point releases add various VNC and LDAP updates to the winter’s 7.00 release, which itself added infrastructure upgrades, speeded up scanning, and completed IPv6 support in just about every area. Many distros will have far older versions in their repositories. The Nmap project does provide RPMs, and on Debian- or Ubuntu-based distros, alien can be used to convert them to .deb packages, but compiling from source is usually trouble free – as it was for us on…

“ They are simply dedicated to providing customers with the highest quality VPS service with exceptional uptime and competitive pricing ” Get your listing in our directory To advertise here, contact Luke luke.biddiscombe@imagine-publishing.co.uk | +44 (0)1202586431 About BHost BHost specialises in one thing and doing it right: Linux Virtual Private Servers (VPS). BHost doesn’t sell extras like domain names or SSL certificates – they are simply dedicated to providing customers with the highest quality VPS service with exceptional uptime and competitive pricing. BHost’s customer focus means that their team always goes above and beyond to help. Their platform successfully hosts a whole variety of services, including game servers, office file storage servers, email and DNS servers, plus many thousands of websites. BHost is confident that you will love their service.…

“ When Linux arrived on the scene the motives and momentum of free software development changed. The Linux distros brought their own dynamic and sense of urgency ” “ In discussion with Dirk Hohndel at the Linux Embedded Conference in April, Linus Torvalds remarked: “The desktop hasn’t really taken over the world like Linux has in many other areas, but just looking at my own use, my desktop looks so much better than I ever could have imagined. Despite the fact that I’m known for sometimes not being very polite to some of the desktop UI people, because I want to get my work done. Pretty is not my primary thing. I actually am very happy with the Linux desktop, and I started the project for my own needs, and…

Top 10 (Average hits per day, 19 February – 16 March) This month Mageia re-enters for the top 10 after a long absence, but Mint holds firm as the number one choice for budding Linux enthusiasts. Highlights openSUSE openSUSE’s intent on providing an easy way for all development and packaging processes has seen it steadily climb the top 10 rankings. It’s another distribution that backs up its claim of being clean, modern and easy to use. Arch Despite being originally tailored for seasoned Linux users, Arch has undergone a mini revival of late, helping shed its old skin and reinvent itself as a robust distro. Manjaro The highly intuitive installation system still remains one of the most popular features of Manjaro. Factor in the automatic hardware detection and it’s clear…

“ This kind of problem is for sharpening both your mind and your programming skills ” “ This month we will show you how to find all unique pairs of elements in an array that sum to a given number S. This kind of problem is for sharpening both your mind and your programming skills. Two implementations will be presented, one in C (sumToS.c) and the other in Perl (sumToS.pl). The two variables of the process are the size of the array and the value of S as well as how S is related to the current element. Here, the elements of the array will be hardcoded but if you want to make your program really valuable, you should generate the elements of the array randomly. The number S will…

The number of internet-connected devices is growing at an alarming rate, so much so, that regulation is needed to keep standards up. Introduced last year and now about to enter its next phase, IoTivity is another project hosted by The Linux Foundation, which has managed to implement a new framework that provides a standard so devices built for the IoT will be able to work together, no matter who made them. So far the project has had some massive success and has spurred on some big developments in the field of IoT. Its latest iteration, made available earlier this year, had a big focus on security, masking many of the flaws found in some of the leading internet-connected products on the market. It has helped ease many developer’s worries about…

Convergence is the stand-out feature of Ubuntu 16.04 – it describes the convergence of the Ubuntu operating system across device platforms, such that this is now the exact same code running across Ubuntu on your desktop, your smartphone and the tablet, as well as servers and IoT devices. What this unified code base enables is the implementation of software that just works across all of these devices, without having to be individually ported to each one. We asked Jane Silber just how deep this convergence goes – whether it is simply responsive design, with the UI reflowing to fit that detected hardware, or whether Ubuntu is working at a deeper level, deploying specific parts of the kernel. “It’s a very good question,” begins Silber. “Is it just responsive design? I…

“ OpenShot 2.0, a Kickstarter success story, aims to become the video editing tool for Linux ” Editing videos is becoming increasingly common on mobile devices, which means that desktop tools need to be able to offer a better collection of features. While a few video editing tools are available for Linux, they’re an eclectic bunch, struggling to offer the all-important combination of features, comprehensive export options and an intuitive user interface. OpenShot 2.0, an open source app developed with the help of a Kickstarter campaign, aims to change that, by combining those three elements and becoming the de facto video editing tool for Linux. Video editing is about more than just sticking a few clips together; you need to start by importing the video files you wish to edit…

“ systemd is a separate project that existed long before CoreOS. However, CoreOS used the systemd approach and built fleet upon it ” Resources CoreOS www.coreos.com CoreOS is known as the new operating system meant to run containers without any friction. CoreOS’s real USP is, however, the ability to let you manage and run multiple containers with minimum effort. Here we will examine the subject in some depth and learn the working of various CoreOS sub systems. 01 CoreOS cloud formation on AWS To see CoreOS features in action, it is important to have a whole cluster running CoreOS. Only then can you see how changes on one node are propagated across the cluster. CoreOS recommends a minimum cluster size of three nodes. It sounds like a huge task to…

There is a Python library for Logitech Media Server (https://github.com/jinglemansweep/PyLMS), which allows you to automate various tasks. Check out the code below to write an application that pings your phone and pauses the players once your phone drops off the wireless network (indicating that you’ve left the house). Once you return, the application can press play. Start your script It makes the most sense to set your script up on the server: Finally, make the script start at boot: Then enable the service and reboot to test it: Full code listing COST OF IMPLEMENTATION Assuming you already have an old Pi or two lying around, this can be a fairly cheap project – there are plenty of good quality class T speaker amps around that you can get for £20…

We have seen that the key part of object detection within an image is the cascade file. When you open one up, you will notice that it doesn’t seem to be very complicated. The complicated bit is in the encoded data that defines that features within the cascade algorithm that are used to identify the object. This data needs to be discovered through a training step where the relevant OpenCV functions look at images that both have the object in question and images that do not have the object. You need a much larger set of negative images compared to positive images. For example, the author of the blog entry at http://coding-robin.de/2013/07/22/train-your-own-opencvhaar-classifier.html needed to use a set of 40 positive images and 600 negative images in order to identify bananas…

“ Robolinux boasts the easiest integration from Linux to Windows that we’ve seen in some time ” RAM 1GB Storage 4GB Specs Based on Debian Available from https://www.robolinux.org To garner a user base, both established and new distributions need to offer something a bit different without overcomplicating the user experience. It’s a surprisingly tricky balance to get right. Robolinux won’t be a new name to a lot of Linux enthusiasts, but it has undergone some big changes to pioneer some intriguing features and improve its desktop experience. Perhaps what will please most users that are considering giving Robolinux a try is its deep integration with MS Windows. There’s support for all native Windows programs and different variations of the OS can be installed through Robolinux’s one-click system. No matter what…

Nikola is a static site and blog generator – “In goes content, out comes a website, ready to deploy” – for anyone comfortable with the command line, who wants a quick and efficient way of making a website. Handling tags, feeds, archives, and comments, and accepting input in reStructuredText, Markdown, Wiki, BBCode, Textile, and HTML, Nikola is one of the most flexible of the many static site generators out there. Unlike popular PHP blogs and CMSs, static site generators benefit from smaller codebases with simple, logical layouts – Nikola really stands out here, and also in the speed with which it builds your site thanks to incremental builds with the doit automation tool. Nikola also takes care of sitemap generation, and has a handy way with image galleries and slideshows.…

A brand new release of the Steam client is now available for users across desktop and mobile. What will please most Linux users is that the dodgy integration of the Steam controller on their desktops should now be a thing of the past with the new changes. Key bindings have been revamped, allowing for users to create their own ‘action sets’ and mode shifts when both in and out of game. The current suite of bindings has also been added to with the introduction of a screenshot function and a secondary binding to load an on-screen keyboard. The lack of mode shift buttons has been a bugbear for many a Steam Linux user, so the implementation of the A/B/X/Y to fill the gap will be pleasing, but based on initial…

“ It’s surprising, the lack of cohesion that’s currently around, so it was our aim to make some changes ” “ Could you give us a general overview of what the Zephyr Project is? The Zephyr Project is an open source effort to build a secure, real-time operating system (RTOS) for the Internet of Things (IoT). This is for the devices smaller than the smallest Linux; the target resource size for example are devices with 8-256kb of memory. For those unaware, there’s a vast amount of devices with these sort of memory restraints, so it’s imperative that we catered for their needs with the Zephyr Project. It’s something that hasn’t really been attempted before and we’re happy with what we’ve managed to actually achieve from it. What were the key…

Ask any number of people in the industry about the pioneers of IoT development and it’s likely that Intel will be a name that’s commonly mentioned. The IT giant has been a big player in bringing the main concepts behind IoT development into the public domain, primarily thanks to its highly successful developer kit. Intel’s IoT Development Kit is an all-in-one solution that combines both software and hardware into one unique package. Users will find everything they need to get started, with a development board alongside Eclipse, Arduino IDEs, IoT Cloud Analytics and much, much more. Intel’s vast array of software that ships with its development kit has all been tailored with different requirements in mind. XDK is best used for getting your devices connected easily, while Eclipse can be…

“Let me just tell you what’s going on,” begins Krishnan, EVP & GM for Canonical’s Cloud. “Cloud has been around as a buzzword for at least seven or eight years now, and a reality – people building things – I’d say for the last three or four. The notion of things becoming software-defined, as opposed to a piece of hardware that’s static, has gradually taken hold. Put those things together and you get an explosion of people essentially taking things that were previously thought of as static and making them increasingly software-defined, and using the principles that people have learned from the cloud to bring those to life, architecture-wise and so on. So, an example of what that would look like: take Netflix, the poster child for how you run…

“ Knoppix has a wide community and a number of support outlets. When you are stuck, there are a number of places you can go to get help ” Resources Knoppix on First Time Linux linux.activityworkshop.net/trying_it_out/what_is_knoppix.html Introduction to Knoppix www.pcmag.com/article2/0,2817,1819549,00. asp Understanding Knoppix www.brighthub.com/computing/linux/articles/63910.aspx Getting started with Knoppix www.freesoftwaremagazine. com/articles/knoppix_ intro Knoppix is a good example of a live Linux system – meaning that you can run everything from a bootable CD (as opposed to running from an installed system on the hard drive). One of the most useful things you can use Knoppix for is using Knoppix CD as a rescue disk – if you have installed Linux and the configuration goes terribly wrong and it stops being able to boot, you can still boot from a Knoppix CD…

Resources A text editor such as Emacs or vi The Go compiler Go is an open source systems programming language that makes it easy to build reliable and efficient software. On a Debian Linux system you can install Go as follows: If you execute apt-cache search golang you will find that there exist a plethora of packages related to Go that you can also install. Find out the version of Go you are using with: As the latest stable Go version is currently 1.6, if you need to install a newer Go version on your Linux system, visit https://golang.org/dl/. The Go programs we’ll take you through here will be relatively easy, but upcoming Go tutorials will include more advanced code so stay tuned! All About Go Go tries to bring…

I play a lot with historic norms and standards, I give objects new functions, new values Love Hultén’s passion for retro gaming, stunning design and the Raspberry Pi has culminated in some of the most breathtaking handheld consoles in recent times. Like it? If you’re on the lookout for a slightly bigger console that still uses the Raspberry Pi as its core computer, make sure to check out Hultén’s numerous other projects. You can find all the relevant details and availability information over on his site at www.lovehulten.com Further reading Emulation on the Raspberry Pi is easier than you might think. For those interested, make sure you read up on the likes of the heavily used RetroPie, or RetroArch, which arguably produces a crisper gameplay experience. As ever, make sure…

What you’ll need • Article’s Github repository (http://github.com/alexellis/ rpi-display) • Two Raspberry Pis • Pimoroni scrollphat (optional) • Soldering iron and solder We are going to create a networked sensor display with the Pimoroni scrollphat. We’ll take a look at the hardware, what’s included and how to install the required Python libraries. Then we will tour the library’s source code and code some examples that have been contributed by the open-source community through GitHub. Once we are familiar with the library, we will go on to set up our chosen sensor on the first Raspberry Pi and connect the screen to our Pi Zero. We’ll learn about how to use Redis (an open-source pub-sub noSQL database). Redis is our connective tissue, publishing events that our Zero will subscribe to and…

FidoCadJ is a cross-platform, vector graphics editor, with graphical libraries for circuit diagrams and PCB layouts. It will do many other graphic tasks quite well, but its built-in set of electrical symbols indicate where it will likely be of the most use. Requiring Java 7 – installation is just downloading the jar, then running with java -jar fidocadj.jar – this app has been one of the most stable Java programs we’ve tried for a while. FidoCadJ is compatible with the Windows program, FidoCAD. Drawings can be exported in PDF, EPS, SVG, PNG, JPG, and LaTeX – via PGF/TikZ. Between FidoCadJ users, drawings can be exchanged in its own compact text format, and there are examples available on the website. Should the extensive library not contain the component that you need,…

Abderrahman Taha’s MathMod is a mathematical modelling app to visualise and animate “implicit and parametric surfaces, either with 3D or 4D hypersurface plotting.” Equations can be written in MathMod’s JSON-compatible scripting form, using the simple built-in editor, and exported as OBJ (to use in Blender) or K3DSurf format. This year has seen the major 4.0 release, then this substantial feature update. Written in C++ and JavaScript, on our LMDE test machine we just had to grab libqt5opengl5 and its dependencies. MathMod ran flawlessly, and we were soon looking at a number of equations in a new way. “Math for fun” says the window title of the visualisation, and this is a program that makes equations meaningful by showing them as things of graphical beauty, little abstract works of art. In…

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