Linux User & DeveloperNo. 155的目錄

This issue » Home automation with Pi » Virtualising Linux machines » Software debugging techniques » Meizu MX4 Ubuntu Edition reviewed Welcome to the latest issue of Linux User & Developer, the UK and America’s favourite Linux and open source magazine. Containers are very much in the public eye right now, particularly with recent developments like the launch of the Open Container Project, but virtual machines aren’t going anywhere just yet – pairing the two technologies in a hybrid setup can be more beneficial than using either alone. This month we’re getting you up and running with VirtualBox, QEMU and KVM; three tools that will enable you to create powerful headless servers, emulate different processor architectures and also create testing environments with your distros of choice, or even preserve an…

Canonical has launched a new networking system designed to vastly increase the number of IP addresses available to containers without adding complexity, dubbed the Fan. “It’s called that because you can picture it as a fan behind each of your existing IP addresses, with another 250 IP addresses available,” explained Canonical founder Mark Shuttleworth of the project. “Anywhere you have an IP you can make a fan, and every fan gives you 250-times the IP addresses. More than that, you can run multiple fans, so each IP address could stand in front of thousands of container IP addresses.” The Fan system was conceived by Mark Shuttleworth and John Meinel, and implemented by Jay Vosburgh and Andy Whitcroft, in order to provide additional addresses for any host system in a local…

“Half a century ago, Marshall McLuhan wrote: “The medium is the message. This is merely to say that the personal and social consequences of any medium – that is, of any extension of ourselves – result from the new scale that is introduced into our affairs by each extension of ourselves, or by any new technology.” Fifty years before the fact, he could have been describing the World Wide Web. The Web is radically changing the ways we perceive and react to the social forces that shape and are shaped by the world in which we live. Before the invention of the printing press and the upheavals of the industrial revolution, society depended almost exclusively on oral communication. Books were the preserve of elites, monks and scribes, who were invested…

Top 10 (Average hits per day, 4 June – 5 July) This month Highlights Mageia 5 Originally a fork of Mandriva, the release of Mageia 5 couldn’t have come at a better time as the company behind its parent distribution folds. Its latest release includes UEFI support, an upgrade to Linux 3.19, KDE 4.14 and GNOME 3.14. Linux Mint 17.2 RC A release candidate for the next version of the chart-topping distribution, Mint 17.2 includes performance enhancements, improved support for multiple sound back-ends, and tweaks to the bash terminal. Finnix 111 The Debian-based Finnix developed by Ryan Finnie now includes experimental support for ARM processors with hard-float hardware, primarily the Versatile Express A9 platform. Latest distros available: filesilo.co.uk…

“This column will focus on finding out if a word is a palindrome. A palindrome is a word, phrase or sequence that reads the same backwards as forwards. We will deal with words but it is easy to extend the code to also support phrases or sequences. The first implementation (palindromeRev.pl) will use an unorthodox method: it will compute the reverse of the given word and compare the original to the reversed one. It is easy to understand why it is not very efficient: the reverse() function does not stop until it has reversed the whole word; the longer the word, the bigger the delay. A more rational approach would be to compare the first and last letters of the word, then the second and second-to-last letters and so on,…

Virtualising Linux machines is an important skill and tool for any modern Linux user, coder or sysadmin. Virtual environments with isolated Linux distros are excellent for testing all manner of things that may be either dangerous or damaging to your distro, or just might react differently in various versions of Linux. Creating virtual machines (VMs) can be simple if you go for some of the more basic methods, but there’s a lot more that you can do with them than just install an alternative distro. You can use these techniques to create a virtual version of an old operating system so that you can keep using some specific software, or for a more private online environment. In this feature we’re going to explore three of the best ways to achieve…

QEMU is not so much a virtual machine software as it is an emulator, allowing you to run operating systems and Linux distros on it by emulating a processor. It doesn’t just emulate your normal processor, though; it allows you to run on x86/x64 systems while giving you access to an emulated ARM, MIPS and other processor styles. This is excellent for development and testing, but it’s also a bit trickier than other forms of virtualisation and doesn’t allow you to quite install like you can with VirtualBox or KVM. However, you can more easily run an image of a hard drive with it. 01 Get QEMU First we need to install QEMU on your system – it’s supported by most Linux distros in their repositories, so in Ubuntu you…

Resources ServerWatch bit.ly/1HdZhOW Loggly bit.ly/1CqZZLO Slicehost bit.ly/1RlYmG3 Tecmint bit.ly/1SaDWLn bitnami bit.ly/1KWPHoi Web servers are considered to be the easier targets for hackers. Since a web server is usually exposed to the entire universe, it’s pretty important to secure it. This is the reason why the sensitive information (such as credit card numbers) stored on a web server are always encrypted. Apache, despite competition like NGINX, is still the most popular web server. Apache is an open source web server and developers across the world keep on working constantly in order to improve its performance and level of security. Apache enables you to monitor two types of information – server configuration information and server status. As expected, server status information is dynamic. By using Apache server’s status monitoring capabilities, it is…

Resources GCC compiler Text editor This is the second and final part of an article dedicated to revealing how it’s possible to develop your own Linux shell. The name of the shell is lud and its source code file is now named ludv2.c; the initial version of ludv2.c is a copy of the lud.c file developed back in the first part. In this concluding article, we will be adding some new features in addition to advancing a few existing ones in order to improve the shell. If, at any point, you feel that you do not quite understand what is going on, it is always a good idea to go back and read the first article again. If you missed out on the issue, head to www.imagineshop.co.uk to order yourself…

What you’ll need Python 2 Pygame IDLE Python IDE Game assets Videogames have come a significant way since their early days, and in recent years it’s become even easier to tell a gripping and compelling story through the medium. A great way to tell a pure story is through the genre of visual novels. These interactive novels are extremely popular in Japan, though they’re gaining traction in the rest of the world, and usually have the player click through a story and make decisions as they go to experience different plot points and endings. In Python, this is a relatively easy project to create, but with the addition of the pygame module we can make it easier still and more expandable for the future. Pygame adds better support for positioning…

One major issue with using Cython is that you are dragged back into the development cycle of compiled languages. In order to test new code, you need to write, compile, then run these changes in order to see how they behave. If the code you are writing isn’t too complicated, then a different option you can choose is to use pyximport. Pyximport is provided through the Cython package, and enables you to have your code compiled on the fly when you need to use it. In order to use it, you need to import it and run the install function: Then, when you import your pyx file, it gets silently compiled. However, one issue is that you don’t have much control over how this compilation is handled. In most cases,…

Q: So how do I update my distro? Will it happen automatically? A: Some distributions include a rather useful version updater, such as Ubuntu. They will usually prompt you if an update has become available, where it will update and add any necessary packages while keeping your files and settings. Others do not have this process, so you’ll need to back up your files and install the updated version of the distro. It’s a good idea to keep an eye out for any updates that might affect your specific system. Q: I’m on an LTS (Long-Term Support) Ubuntu, and the upgrade prompt is not showing up. What’s the problem? A: Open the Update Manager and click Settings. Go to the Updates tab and look for the menu with ‘Notify me…

To access FileSilo, please visit www .filesilo.co.uk/linuxuser 01 Follow the instructions on-screen to create an account with our secure File Silo 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 alphanumeri ccode 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…

Rob Zwetsloot studied aerospace engineering, using Python to model complex simulations. Recently, he came dangerously close to enjoying an iPad and, as penance, is now orchestrating a hive of Linux VMs (p.24) while upgrading our PCs (p.36) and writing a visual novel in Python (p.62). He dreams of Ubuntu tablets. Jon Masters is a Linux kernel hacker who has been working on Linux for some 19 years, since he first attended university at the age of 13. Jon lives in Cambridge, Massachusetts, and works for a large enterprise Linux vendor. You can find his brilliant Kernel Column on pages 12-13 this month. Liam Fraser is the creator of the RaspberryPiTutorials YouTube series and volunteers as a Linux server administrator for the Raspberry Pi Foundation. Turn to page 50 to read…

“Linus Torvalds released the final 4.1 Linux kernel, saying that it had been “a very quiet week after the [unusual] 4.1-rc8 release”. As we noted last issue, Linus had decided to add another week (Release Candidate 8) to the schedule for Linux 4.1 due to the timing of his annual vacation coinciding with the original release target, and because there were a few small issues (for example, potentially nasty data corrupting problems found in the “md” RAID drivers as noted in the -RC8 announcement) that still needed a little time to shake out. Overall, Linus was happy with 4.1, which he thought was a good thing “considering that 4.1 will also be a LTS release”. LTS (Long Term Stable) means that Greg Kroah-Hartman (Greg-KH), and potentially other kernel maintainers subsequent…

KVM USEFUL FOR Emulation and virtualisation on servers for more dedicated VMs KVM is the set of virtualisation modules that are built into the Linux kernel – not a keyboard and mouse switch. The benefit of having KVM built into Linux itself is that it makes it easier to turn it into a dedicated hypervisor, maybe the kind you’d use on a server, without requiring extra layers of packages and other software on top of it. It’s quite quick to set up, especially via a graphical method, and has some good basic functionality between host and guest. It can be used on the command line very easily if you plan to have a headless server. VirtualBox USEFUL FOR Testing software, development or any kind of activity where you’d like to…

Also known as Kernel-based Virtual Machine, this allows for a Linux distro itself to be the hypervisor for its own virtual machines. This requires hardware virtualisation support in Intel and AMD processors (Intel VT-x and AMD-V, respectively), but it supports a lot of different Linux distros and other operating systems. It can be managed graphically so it’s about as easy to use as VirtualBox while also being a little more efficient in some cases. KVM is good for both desktops and servers used for creating virtual machines, but does require a little more setup than VirtualBox, while also being slightly easier than QEMU. 01 Test compatibility It’s important to first find out whether your system can or cannot actually run virtual machines using KVM, as it requires the hardware virtualisation…

Resources Twitter API key dev.twitter.com Django Twitter Streamer bit.ly/1f3ETbJ Twitter’s API has been ported to many programming languages over the years, and one of these is, of course, the very popular Python. In the past, we’ve done tutorials on using Twitter via Python to create little apps and streaming programs. The various libraries make good use of the API and, with a little bit of tweaking, you can carry out a lot of Twitter-powered functions. Twitter is a web tool, though, but luckily there is a version of Python for the web: Django. Some of the tools have been further ported to Django and allow you to integrate it into websites fairly easily. This can be used for something like a sidebar that has a running stream of tweets from…

Resources SSD hard drive (minimum of 64 GB) HDD hard drive LuckyBackup bit.ly/1L6bifD It’s been a while now since SSD drives have been a thing in modern computing. The price for reasonably-sized drives is now affordable, especially compared to the hundreds you would have spent on 64 GB a few years ago. Large amounts of storage space on SSD can still be a bit pricey, though, with standard hard disk drives giving you far more bang (or in this case, gigabytes) for your buck. There’s also the problem of SSDs having a limited number of times they can be written to, at least compared to HDDs. A combination of both, then, seems like a pretty good idea. In fact, it’s one of the best ways to set up your system…

Components list Raspberry Pi B+ LEDs DHT11 temperature/ humidity sensor Stepper motor I2C bus Sensors The temperature, humidity and pressure sensors used in this model all output their data in real-time to the automation dashboard AppliancesThis stove light is used to represent other appliances you can add, from Nest thermostats to Wemo outlets, and much more Lights PubNub’s LEGO Smart Home uses lots of LEDs to simulate the lights that you would have around your home, like this porch light Doors There’s a tiny stepper motor behind this door that can open and close it at the touch of a button on the dashboard So tell us about PubNub and your LEGO Smart Home. PubNub is a global data stream network. What this means is that, using the PubNub software,…

What you’ll need • Pi Glove or a similar hardware setup In part one (issue 154), we covered the creation and the hardware setup of a wearable tech glove formally known as Project New York. This tutorial shows you how to create a program and write the software to add interaction to the glove’s buttons. Once you have created the basic code structure, you can develop new interactions by coding and adding your own functions. The program is coded in Python 2.7 to ensure all the libraries are compatible with the Raspberry Pi hardware and the Raspbian operating system. On completion, the glove will give you spoken instructions, tell you the current time, take a picture with the Pi camera module and play a random selection of music, all from…

Gavin Thomas is the Editor of LU&D and RasPi. He is an experienced tech journalist with a passion for homegrown projects. If you like this… The Foundation has an excellent guide to getting up and running with the Sense HAT, taking you from the initial hardware and software setup through to displaying text and images, using the sensors and more: raspberrypi.org/learning/astro-piguide Further reading There are more great Astro Pi resources out there in the wild – Dan Aldred rounds up cheat sheets from his school and resources like those on the National STEM Centre site (tecoed.co.uk/astropi.html), and Ben Nuttall’s GitHub page has some starter projects to play with (github. com/bennuttall/ astro-pi-examples). Why do I keep on hearing about Astro Pi – is it some sort of space-age Raspberry Pi model? Not quite,…

Pros A much nicer chassis than the Aquaris, and a far better screen that actually holds up against other modern smartphones Cons Ubuntu is still lacking in apps and scopes, and relying on mobile web clients for all the big social media apps CPU Octa-core, 2 GHz (MediaTek MT6595) RAM 2 GB Operating system Ubuntu 15.04 Display 5.36-inch IPS screen, 1920 x 1152 pixels (418 ppi) Camera 20.7 megapixel rear camera, 2 megapixel selfie camera Storage 16 GB Price €299 / £212 Finally, after months of waiting, the second Ubuntu Phone is upon us. The original – the BQ Aquaris 4.5 – was a serviceable phone but the poor specs and extremely early version of Ubuntu that accompanied it made it seem a lot more like an early development phone…

Dedicated server listings Dedicated and Shared server listings Got a deal you think we should list? Whether you’re a hosting firm or a happy customer who wants a favourite provider listed, drop us a line with the details! linuxuser@imagine-publishing.co.uk Sponsorship opportunity Bring attention to your brand by sponsoring this section. Contact Luke Biddiscombe on +44(0)1202 586431 GET YOUR LISTING HIGHLIGHTED! CONTACT LUKE luke.biddiscombe@imagine-publishing.co.uk +44(0)1202 586431…

I am somewhat desperate. I’ve been looking for a solution for days and have not found anything (and simply cannot believe that I’m the only one in need of this). Okay, this is what I am looking for: How can I make my smartphone (Android) dial a phone number that I see on the screen of my computer (running Ubuntu). Let’s say some number from the signature of an email in Thunderbird, or a number I googled in, say, Firefox or the like. There are apps/software to do exactly that for Windows. But Linux? I type numbers I see on the screen into my smartphone a few times a day. This is such a waste of concentration and could be done so much faster with the right app! Anyone have…

The Linux Foundation has announced that its Core Infrastructure Initiative has released nearly $500,000 in funding for three security-related projects: the Debian Reproducible Builds project, Hanno Böck’s Fuzzing Project and Pascal Cuoq’s TIS Interpreter, while also providing for the hiring of Emily Ratliff as senior director of infrastructure security for the Core Infrastructure Initiative itself. One of the first two people to work on base systems security at IBM’s Linux Technology Centre, Ratliff is known for her contribution to the first Common Criteria Evaluation of Linux and has worked with the Trusted Computing Group, GlobalPlatform, and holds Certified Systems Security Professional status. “I’m excited to join the Linux Foundation and work on the Core Infrastructure Initiative because improving the security of critical open source infrastructure is a bigger problem than…

The Linux Foundation has begun accepting submissions for its 2015 Linux Training Scholarship Programme, which includes two new categories aimed at younger users and beginners. “Our training and certifying of Linux professionals is among the most important work we do. These individuals will manage and advance the Linux systems of tomorrow,” claimed the Foundation’s Amanda McPherson of the project. “This annual scholarship program is a key piece of that work and allows us to reach people we might not otherwise, increasing access to our learning materials and, this year, the Linux Foundation Certifications.” As well as the existing categories, the 2015 programme includes two new entries: Linux Newbies, aimed at those who have completed the Intro to Linux edX courses but have no other experience; and Teens-in-Training, marking the first…

Arduino LLC has announced the launch of a new web-based integrated development environment (IDE) for its programmable microcontroller development boards. Based around Adobe’s Brackets Editor, the alpha release of the open source Arduino Studio supports Linux and other platforms as well as being available as a Brackets Extension to run within a browser on any device. Arduino Studio is described by the company as “a work in progress,” designed to be suitable for use as a stand-alone, cloud-based or on-board embedded IDE. As well as a new user interface, Arduino Studio includes code completion and an in-line quick language reference system, both designed to speed up coding for experienced Arduino users and make the platform as accessible as possible. While Arduino Studio can be expected to replace Arduino IDE in…

Developers at the US National Security Agency (NSA) have been publicly and actively involved in development of Linux (as well as features such as the Security Enhanced “SE” Linux that they originally sponsored) for many years. It is always interesting when they surface with concerns (and, in this case, apparently our best interests for enhanced security at heart). Such was the case when Stephen Smalley raised concerns over the “credential faking” support that has been added to the controversial “kdbus” in-kernel D-BUS implementation, still facing an uphill battle in its quest to merge into Linux. Many see kdbus as overkill, moving code into the kernel that rightfully belongs in userspace, rather than optimising what is already in userspace today. The latest concern relates to retaining compatibility with existing userspace D-BUS…

Resources AWS root account Web visitors don’t appreciate having to wait for a page to load each time they tap or click. If you want that bounce rate to drop, give the public what it craves for in a website: speed, speed, then some more speed. Nothing works miracles the way a high-performance web server does. In benchmarks, NGINX can crush its competition. It can serve roughly double the number of requests of its fastest competitor (Lighttpd) and eight times that of the overall market leader (Apache). It has none of the problems of the other web servers (Lighttpd suffers from memory leaks and Apache sports an overall level of code ‘seniority’ that qualifies it for retirement). NGINX was designed from the ground up for the cloud era of elastic…

Resources GDB Manual bit.ly/1GbYIDi Glibc Heap Consitency-Checking bit.ly/1Hi5gSC Why Programs Fail bit.ly/1KS8j99 The Art Of Debugging bit.ly/1Bd1jBP From time to time, a certain piece of software fails. Whether it’s due to a defect that lies in its code or within a buggy external library the software depends on, the result is somehow the same: the program usually crashes. In this scenario, an ICT expert is meant to solve the issue or to find a way to circumvent it. However, more often than not, the ICT expert will not have any previous knowledge of the software, so a comprehensive and thorough analysis without the right tools and techniques will prove an insurmountable task. To make matters worse, sometimes the ICT expert will be dealing with proprietary software for which sources will…

01 Start heimcontrol.js on boot Before we start adding devices, it makes sense to start heimcontrol.js on boot. To do this, we can add a line to /etc/rc.local which is a script that gets ran at boot by the root user. The file needs to be edited with sudo and your favourite editor, for example: Add the following line before the line “exit 0”: Heimcontrol.js will be started automatically at boot from now on, but for now you can start it with node/home/pi/heimcontrol.js/heimcontrol.js. 02 Add the camera feed Go to Settings and select Webcam. Set the method to Streamer and the devices as /dev/video0. Pick an interval; we picked two seconds but you can pick any interval you like. Shorter intervals are more feasible on a Raspberry Pi 2, as…

What you’ll need • Sensly HAT sensly.uk The Sensly is a smart module attached to the Raspberry Pi. It has its own microprocessor that can handle analog data and handle sampling from various sensors without the need to waste your Raspberry Pi’s processing power. There are three different gas sensors attached to the board, allowing you to sense a multitude of gases, as well as humidity and temperature sensors. Plus, this Raspberry Pi HAT can be easily extended with its array of analog ports and an I2C interface. In keeping with the Raspberry Pi way of doing things, the module also provides a Python API that does all of the hard work for you. All of the maths, calibration and error correction is handled by the API itself, allowing you…

“The previous two articles of this series looked at profiling code, to see where to apply your skills, and then optimise the existing Python code.” In those cases, you have the option of outsourcing troublesome parts to an external language and compiling that code to machine language. The most common technique to do this is to use Cython (www.cython.org) to take C code, compile it to machine code, and then use it within your Python code. The first item you need is a C compiler that Cython can use. On Linux systems, the default compiler is GCC. To be sure that you have all of the tools, you can use the command: The second item you need is the Cython package for Python. If you want the latest version available…

www.filesilo.co.uk/linuxuser YOUR BONUS RESOURCES ON FILESILO THIS ISSUE, FREE AND EXCLUSIVE FOR LINUX USER & DEVELOPER READERS,YOU’LL FIND THESE GREAT RESOURCES… » 4 Latest distros, including the latest Linux Mint LTS and Mageia 5, reviewed on pages 84-85. » 16 Best FOSS packages, including VirtualBox 5, FUZE BASIC V3, our group-tested SSH GUIs and more. » Watch The Linux Foundation, Red Hat and Raspberry Pi video guides, tutorials and webinars. » Code and assets for this issue’s Coding Column, plus the Visual Novel, Program a Shell and Pi Glove tutorials. FILESILO – THE HOME OF PRO RESOURCES DISCOVER YOUR FREE ONLINE ASSETS 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…