Linux User & Developer的No. 157目录

This issue » Launch a Docker container » Run Windows software in Wine » Discover systems programming » Build a Raspberry Pi music visualiser Welcome to the latest issue of Linux User & Developer, the UK and America’s favourite Linux and open source magazine. This month we’re focusing on the developers among you: starting with a big guide to systems programming in C that we’re going to follow with a run of tutorials over the coming months (page 20), we have some excellent guides that will get you started with C# programming, Docker containers, automation and security on AWS, and a pair of tutorials on R and D3.js to help you manipulate and visualise data. We’ll be revisiting some of these before the year is out, so stay tuned. With…

“Congratulations on recently making the project announcement! How long have you been working on Plasma Mobile now? In earnest, about four to five months. It started as a very proof-of-concept thing about a year ago, and around the change of year we knew that we could actually bring up a Plasma UI on a phone. So then we started to figure out the stack – how things should work together, how to get it working on the Nexus hardware. We tried to move to the Ubuntu-based stack but had huge problems getting libhybris to work: kernel and graphics driver problems. That actually threw us back about two to three months and it was basically solved by moving to KWin completely. Then the guy who does development on KWin could actually…

This feature is about systems programming and is the first in a series of articles that will help you understand how various Linux utilities and servers are implemented, as well as what is going on behind the scenes on a Linux system. It would be good to have a basic knowledge of C and know how to compile and run a C program before continuing. By the end of this systems programming series, you will be able to develop your own system utilities and understand the brilliance of Unix that lies in its simplicity and consistency. It is also very interesting to realise that the principal functionality of Unix system software is relatively easy to implement and does not usually take lots of code. Most of the C code is…

Recent bloat to iTunes has seen it grow from the relatively light, focused, powerful music library app of the early days, to a tottering mass of scarcely needed functionality that is the multimedia equivalent of MS Office. There are plenty of Linux alternatives to iTunes too, although almost all have their drawbacks. Nevertheless, for users with purchased media trapped inside Apple’s walled garden, iTunes has its advantages and many Linux users need access to it without having to dual boot. Unfortunately, running iTunes on Wine is not always easy and many go to the extent of keeping a Virtual Machine (VM) on standby, running a recent OS X or Windows version just to run iTunes. There is a mass of contradictory information only a web search away on installing iTunes…

Resources Docker docker.com Linux containers provide a simple way to run applications in an isolated environment. Applications are bundled with the libraries and other required binaries, and then run in an isolated manner via containers. Containers have been around for some time – projects like LXC, OpenVZ and so on were released around 2005 – but things really changed with Docker. Not only did containerisation go mainstream among users, but more businesses are now using Docker for their production systems. Before we jump onto Docker and its basics, let’s try to get some clarity over one of the basic questions – the difference between containerisation and virtualisation. Virtualisation involves creating a target kernel on the host machine, so you will have as many kernels as virtual machines on your system.…

Resources MonoDevelop monodevelop.com One of the design goals of Microsoft’s .NET framework was the creation of a truly portable runtime environment. This aim was furthered by the release of the specification for the intermediary language, a decision that has led developers to suffer under the pain of commercially available decompilers from day one. Redmond’s interest in openness even went so far as to rename the intermediary language from Microsoft Intermediate Language to Common Intermediate Language, although these steps were not purely altruistic. Microsoft sought to motivate third parties to create runtimes for their operating system – a project that succeeded largely due to the work of the Mono team. C#, however, is not of primarily historic interest. It is one of the most commonly used ‘traditional’ programming languages; its compilates…

Components list Raspberry Pi B+ Real-time clock module 8-port Ethernet hub Raspberry Pi power supply 6 x WizYasep boards 120 x 150W power supplies 50,400 x RGB LEDs (3/bulb) 4 x infrared sensors LED bulbs The ceiling is made up of six main sections containing 2,800 bulbs each, for a total of 16,800 bulbs holding 50,400 RGB LEDs, and thus over 150,000 individual LED components Sensors A pair of sensors, placed at each end of the pathway, are used to calculate when passengers are moving in a particular direction WizYasep Designed to transmit and transcode data flows through Ethernet connections at high speed, low latency and low jitter, the WizYasep controller board is perfect for networked LED displays Raspberry Pi Conductor of the light display, the Raspberry Pi processes the…

What you’ll need Raspberry Pi Twilio account Text messaging, or SMS (Short Message Service), has become a staple of everyday communication. What began life as a 40 pence message service is now offered by most tariff providers as an unlimited service. Twilio, a cloud communications company, enables you to send SMS messages for free from your Raspberry Pi to a mobile phone using just six lines of code. 01 Set up your Twilio account The first step of this project is to register for a Twilio account and Twilio number. This is free and will enable you to send an SMS to a registered, verified phone. Once signed up, you will receive a verification code via SMS to the registered phone. When prompted, enter this onto the Twilio site to…

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 16-17 this month. Richard Smedley has been helping businesses and community organisations of all sizes to move to GNU/Linux since the 1990s, and doesn’t expect those he works with to share his love of Emacs. Well, maybe a little. This month he dives deep into Wine to show us how we can run essential Windows software natively (p.28). Liam Fraser is the creator of the RaspberryPiTutorials YouTube series and volunteers as a Linux server administrator for the Raspberry Pi Foundation. Liam…

1 Application Dashboard A new full-screen menu, the Application Dashboard, takes over from the Application Menu with a focus on making full use of high-resolution screens. This is in order to find you your software and files as quickly as possible, while including easy keyboard navigation and type-to-search functionality for the mouse-averse. 2 Wayland preview The latest Plasma release brings the new kwaylandintegration repo, giving those who like to live on the cutting edge a chance to play with the new Wayland windowing system, without having to give up on their existing KDE framework integration. 3 Network applet graph If you would like to keep an eye on historical network traffic, you will be pleased to know that a new graph is set to appear in the network applet. The…

Seagate’s enterprise-grade storage platform, Kinetic, is now an official Linux Foundation Collaborative project, with companies including Western Digital, Toshiba, Dell and Cisco joining the development effort. Kinetic combines storage devices featuring integrated Ethernet connectivity with a key/value store paradigm claimed to improve the efficiency, scalability and flexibility of enterprise storage. Using open source software and a standardised set of application programming interfaces (APIs), storage developers can use a Kinetic system to reduce the overheads of storage area network (SAN) implementations, taking advantage of features like direct drive-to-drive data transfer via Ethernet, without needing an intermediate host device. Although billed as the Kinetic Open Storage platform, the standard remained under Seagate’s control until the formation of the Linux Foundation Collaborative Project. Now truly open, network and storage vendors have joined and…

The Fedora project has demoted support for 32-bit x86 architectures from its Linux distribution, following a vote by the Fedora Engineering Steering Committee (FESCo). In its late August meeting, FESCo raised a vote on removing support for the i686 32-bit x86 instruction set architecture from Fedora 24. “From my PoV [point of view], nobody wants to support the i686 image,” Haïkel Guémar told attendees. “I’m completely +1 for [in favour of] dropping all of the i686 images/media in f24 [Fedora 24],” added Kevin Fenzi. After some discussion, the committee agreed to change the vote away from a total abandonment of i686 support, to making it a non-blocking deliverable. This means that its absence (should work not be complete in time) would not prevent the general launch of Fedora 24, effectively…

“Linux 4.2 was released by Linus Torvalds, following a slightly longer cycle than usual (eight weeks, rather than the typical seven following the first RC or Release Candidate kernel). The new features in kernel 4.2 mostly concern internal optimisations and enhancements that are more or less transparent to the average end user. Examples include support for System Management Mode (SMM), emulation in KVM that effectively enables KVM-based virtual machines to implement Secure Boot (as used by some Linux and many new Windows systems). This is as well as a completely rewritten implementation of the floating-point context management code on x86 (the bit that preserves the floating-point unit state between task switches) that has “substantial regression risk” for user-visible problems to be discovered as end users hammer it hard with floating-point…

Systems programming is a special area of programming in a Unix environment. Back when Unix was first introduced, the only way to write systems software was by using C. Nowadays, you can program systems software using other languages as well. Most commands that have to do with system administration tasks, such as disk formatting, network interface configuration, module loading, kernel performance tracking and so on, are implemented using the techniques of systems programming. The key difficulty in systems programming is the fact that a wrong system call can make your Linux machine misbehave or, even worse, crash altogether. Most Linux security issues usually come from such wrongly implemented system software, so you should be extremely careful when using system calls because code with bugs can compromise the security of an…

There exist many programming languages that can help you perform system tasks. All programming languages implement their own functions by using C system calls because it is the only interface for talking to the Linux kernel. The example program that is going to be implemented on all six programming languages is a minimalistic version of the cp command line utility. The presented implementations in C++, Rust, Go, Perl and Python are not the only ones enabled or offered by each programming language. They are presented here in order to give you a quick sense of each programming language. C and C++ When it comes to systems programming, C++ can be almost identical to C. Their only difference is that in C++, you can organise your code differently because C++ is…

Resources R project r-project.org RStudio bit.ly/1VLmlgA Zoo package bit.ly/1Ov0whd Chron package bit.ly/1LhClzq The R software deals, processes and visualises data all the time – it is something that can give value to your data. However, what is the point of visualising data if you cannot transform, manipulate and change your data whenever you want, any way you want? This article will teach you many different ways to manipulate and transform your stored data within R. This is very important because most of the time the information you want is hidden somewhere and waiting for you to find it. Additionally, when you have problems with data, it is often a matter of data being in the wrong mode or class in relation to the task you are trying to perform. The…

Resources AWS root account Python Routine maintenance of Linux systems can wear anyone down, even without the need to keep an eye on one’s public cloud expenses. As a result, automation is quickly emerging as the weapon of choice for Linux administrators in the quest for more adequate control of infrastructure and services. Ready-to-use automation tools along with raw cloud APIs have managed to redefine server administration in the cloud. Whether you want to embrace full-blown programmatic orchestration with tools such as Chef, Puppet, Eucalyptus or Ansible, or to simply ensure a reasonable response time from a couple of servers in the cloud at an acceptable cost-to-benefit ratio, automation is the way to go. For all its perceived benefits and sophistication, automation has one major downside: it cuts both ways.…

What you’ll need LED strip USB sound card (we used a Behringer UCA202) Breadboard Female to male jumper cables 3 x TIP120 NPN transistors 3 x 220› resistors DC jack In this feature, we will write a Python script that takes audio as the input, either as a line-in stream from an audio card or as a WAVE file to play. This audio stream will then be filtered into three bands – bass, middle and treble – using the signal-processing library that comes with SciPy. The amplitude of each band is averaged and then mapped to a colour on an LED strip in real time, so that the LED strip changes colour as the energy of the music changes. The amazing results are sure to be the talk of your…

What you’ll need OSMC tv Hard drive Home network Samba Another Linux computer, less than eight years old Thousands of images, videos and music files live in your pocket and it’s likely even more are in your personal cloud or hard drives. While it’s great enjoying these on our personal devices, it’s gratifying to see them on our big TV screens – but this isn’t easy. Do we hook up our laptops? Do we fiddle with a menagerie of wires and resolutions, hoping for a decent image? Will the sound work? All of this is taken care of with a Raspberry Pi 2 and OSMC. OSMC is an OS built to do one thing: put your media up on that big screen. But, how do we get media onto OSMC?…

Why Python? It’s the official language of the Raspberry Pi. Read the docs at python.org/doc “ In the previous issue, we looked at how to turn your Raspberry Pi into an RSS feed reader and how to enable your Raspberry Pi to post an RSS feed for others to read. In this issue, we will continue along the same lines and look at how to add the ability to have your Raspberry Pi post tweets for the rest of the world to follow what is happening. The first step is to find some way to talk to Twitter. Twitter provides a full API that defines how you can send and read tweets. We could work with raw sockets; manually format and send messages, then process the returned results. However, this…

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 Dedicated server listings Dedicated and Shared server listings 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 taking images from a webcam as a snapshot. It’s sending me the files so I know that part is working. Now I need a bash script that will rename the latest file; unfortunately, file names are hard to guess based on sequence numbers. I can only give a partial name like 192.168.0.100-*, where the names are IP, date and time (and many other things) to be searched for. Let’s say I want to change the image to something like mycam1image.jpeg . After that’s done, I then want to delete the existing old files, in the same manner as rm -rf 192.168.0.1-*. Consequently, only the latest file will be replaced and previous files will be removed. Now, I must detect the latest file, as if in some cases there…

To access FileSilo, please visit www.filesilo.co.uk/linuxuser 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…

The Linux Foundation has announced a project in partnership with industry giants to advance an enterprise-grade platform for Linux on mainframe devices, unsurprisingly dubbed the Open Mainframe Project. The project brings together industry giants ADP, CA Technologies, IBM and SUSE as founding platinum members, while BMC, Compuware, LC3, RSM Partners and Vicom Infinity join as silver-level members. Its formation comes as industry demand for mainframe systems resurges thanks to interest in cloud computing and big data topics. “Linux today is the fastest-growing operating system in the world. As mobile and cloud computing become globally pervasive, new levels of speed and efficiency are required in the enterprise and Linux on the mainframe is poised to deliver,” claimed Jim Zemlin, executive director at the Linux Foundation, at the project’s announcement. “The Open…

“October is the 30th anniversary of the founding of the Free Software Foundation, a moment that was barely noticed in its time but can be said to have transformed the development of software. The concepts that define free software grew out of Richard Stallman’s experiences at the AI Labs at MIT, his personal history with the development of the LISP machine and his disputes with James Gosling over the licensing of Emacs. As early as October 1981, Stallman had written: “Emacs does not cost anything; instead, you are joining the Emacs software-sharing commune. The conditions of membership are that you must send back any improvements you make to Emacs, including any libraries you write…”, which could be seen as an early attempt to define copyleft and the first principles of…

(Average hits per day, 5 August - 3 September) This month Highlights Ubuntu 15.10 Beta 1 Released ahead of the full launch in October, the latest Ubuntu ‘Wily Werewolf’ beta comes in standard, Kubuntu, Lubuntu, Ubuntu GNOME, Ubuntu MATE, Ubuntu Kylin, Xubuntu and Ubuntu Cloud flavours for testers of every type to enjoy. Zorin OS 10 Featuring an Ubuntu 15.04 base, the latest Zorin OS includes a new media player and a neat activity journal that displays files and documents you have worked on throughout the day. Kali 2.0 The release of Kali 2.0 has brought a shift to a rolling-release model. It is designed to make it easier to keep the penetration testing and security distribution updated. Latest distros available: filesilo.co.uk…

“Identifying whether or not a given positive integer is a power of two is not a challenging job, but it needs a lot of processing, especially if the integer is larger than 2^20. Also, it highlights that: a) you should always think carefully before implementing, and b) it is good to have a sound knowledge of mathematics when you are programming. The more areas of mathematics you know, the better. Here is a standard, brute force and recursive Python function (powerOf2.py) that solves the initial problem: Another version uses binary arithmetic (bitwise.py): Put simply, the function checks whether there is more than one “1” bit set in the binary representation of the number variable. As you know, CPUs calculate using binary arithmetic. These calculations are especially fast and happen quicker…

With the release of Linux 4.2, came the opening of the “merge window” (a period of time during which disruptive changes are accepted) for what will become Linux kernel 4.3. Amongst the internally/developer visible changes is a switch to make Virtual Mode 86 (VM86 – as discussed in relation to NMIs) a Legacy feature, scheduled to be removed from future kernels. The main user-visible early feature merged thus far is support for a new “PIDs” controller for the control group (cgroup) subsystem. This is intended to reduce the risk of “fork bombs” (spawning many processes/tasks until the system runs out of resources to allocate additional processes/tasks) by imposing firm limits upon how many subprocesses members of a given cgroup can create once established. There has also been a major reworking…

A C system call is just a normal C function. What makes a system call different from an ordinary C function is the fact that system calls implement functionality that is usually low level and connects the Unix kernel with the rest of the world. Usually, it is a hardware-related service (accessing a hard disk or a network device), process management (creating or deleting a process) or communicating with core kernel services (process scheduling). In other words, system calls enable programs to request services from the operating system that cannot otherwise be accessed by a process. The programs that use system calls are often called system programs. You can think of system programs as containers of system calls that help you perform tasks that deal with the internals of your…

As your day-to-day computer use – from games, through office and collaboration apps, to social media – moves to the web browser, relying on cross-platform, free and open source technologies, there’s a fairly level playing field between Linux and its proprietary rivals, most particularly Microsoft Windows. Before free software advocates rejoice too much, there remains one road block for many users looking to transition away from the spyware-ridden recent versions of Windows: a stubborn collection of legacy or proprietary software available only for Microsoft’s platform. Whether you’re an office user tied to macros written for MS Office, a worker dependent upon custom proprietary software for their day-today work, or a gamer who simply must have their fix, a serious move to Linux will only happen if you can happily run…

Resources Text editor D3.js d3js.org D3 means Data-Driven Documents. It is a JavaScript library that can help you bind random data to the Document Object Model (DOM) and apply data-driven transformations to the document. D3 offers functions that, when applied to DOM elements, can transform the resulting HTML, SVG or CSS documents. It is a powerful piece of software that can do many things and generate extraordinary interactive and professional output. It does not have one single function to draw a circle or any other shape, for example; instead, it has a function that processes the right set of data in order to create a circle. Although this approach makes you write more code, it offers more flexibility and freedom! D3.js also supports code reuse with the help of its…

Resources AWS root account Those who dare to venture into the public cloud quickly learn the value of paranoid security. In the cloud, you are no longer ‘merely’ facing the risk of a catastrophic data loss or data leak. You are now looking at what amounts to an unlimited financial liability for your pay-as-you-go services that scale on demand. Should an unauthorised party gain control over your AWS account, the financial outcome wouldn’t look pretty. Not even close. It is wise to never underestimate human ingenuity, because the impossible may not be so far-fetched after all. Over the last year or so, a series of security vulnerabilities, from Heartbleed through Shellshock to VENOM, struck terror into the hearts of active cloud users around the world. Heartbleed and Shellshock famously exposed…

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 Bodhi 3.1.0 with the brand new Moksha desktop, reviewed on pages 88-89. » 16 Best FOSS packages, including Wine, used in our feature on running Windows apps (pages 28-32). » Watch The Linux Foundation, Red Hat and Raspberry Pi video guides, tutorials and webinars. » Code and assets for this issue’s tutorials: the systems programming utilities, music visualiser and more. LENGTH OF VIDEO TUTORIALS: 20 HOURS www.filesilo.co.uk/linuxuser 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…