Linux User & Developer的No. 158目录

This issue » Learn to program in Vala » Automate actions for log events » Set up the official Pi touchscreen » Find out why Jim Zemlin is a roadie Welcome to the latest issue of Linux User & Developer, the UK and America’s favourite Linux and open source magazine. Following our focus on programming and some of the latest tools to shake up the open source world, we’re taking on a range of core topics this month like containers and DevOps (page 44), systems programming (page 34), computer science (page 56) and more. Plus, we had a chat with Jim Zemlin to learn more about the Collaborative Project and Workgroup announcements made at this year’s LinuxCon Europe, and to understand more about the Linux Foundation’s goals with these and…

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, where he is driving the creation of standards for energy efficient ARM-powered servers “Linus Torvalds announced RC3 (Release Candidate 3) of the 4.3 Linux kernel, saying “as usual, RC3 is actually bigger than RC2 (fixes are starting to trickle in), but nothing particularly alarming stands out.” Following the merge window that is usually the first two weeks of a development cycle, during which disruptive changes are accepted into a given release, Linus will typically post seven or eight Release Candidates. Usually, these will happen once a week on a Sunday (as…

Quantifying the value of an open source project, let alone an entire stable of them, is no simple matter. However, the Foundation has done just that, creating a report based on David Wheeler’s COCOMO (Constructive Cost Model). In 2002, Wheeler used the COCOMO, based on the work of Barry Boehm, to analyse a typical Linux distribution, counting the lines of source code and estimating the amount of development effort required to produce it in person-years (the amount of work one developer can do in a year). He then produced a final estimation of the costs. The Linux Foundation’s report, A $5 Billion Value: Estimating the Total Development Cost of the Linux Foundation’s Collaborative Projects, estimates that there are 115,013,302 lines of source code among its Collaborative Projects. The estimated total…

Real-Time applications have operational deadlines between the triggering of an event and the application’s response to that event which must be met. This enables a guaranteed response time – usually for safety reasons, as with pacemakers. Real-Time Linux is a kernel patch set (CONFIG_PREEMPT_RT) that makes Linux into a real-time system, enabling the control of robots, data acquisition systems, manufacturing plants and other time-sensitive equipment and machines from RTL applications. It’s also important because of the number of bugs in the mainline kernel that it identifies and fixes as part of the patch development. The future of Real-Time Linux has been under threat because of a lack of funding, with the core maintainer Thomas Gleixner – who has worked on the patch set for over a decade – being reduced…

Even though Vala permits the creation of classes not derived from GLib.Object, most developers will be better served by foregoing the small amounts of memory saved in exchange for the more advanced features that are offered. Most importantly, Glib.Object provides a reference-counting rubbish collector that permits Vala to dispose of unneeded object instances automatically. Secondarily, the base class provides a framework for property change notification. This means that clients can register interest in particular variables. If a change is performed via the corresponding method, the callback is then invoked. Finally, GObject is filled with a list of helper functions that will simplify object construction, signal registration and signal management. Those of you who are friends of introspection can also use a few dedicated methods. If a part of your product…

Usually, things will not work the first time and there will be bugs hiding in your programs. Keep in mind that debugging is an art of its own! The hardest part of the debugging process is not fixing the bugs, but to reproduce the bugs on your machine. The fixing part is usually the easiest part of the difficult debugging process. A simple ‘algorithm’ for debugging code in any language includes the following steps: 1) understanding that you have a bug; 2) making the bug repeatable (this step can be very challenging, especially when you are dealing with server software because bugs can happen irregularly); 3) finding out where the erroneous code is (if you have difficulties finding the place of the incorrect code, step-by-step program execution and printing log…

Resources Text editor D3.js d3js.org SVG bit.ly/1igisSF Layouts bit.ly/1EQi7Al This article will continue to explore the capabilities of D3.js, as we began in part one in the previous issue, by creating sophisticated plots. This time you are going to learn more things about how D3.js works and creates its output. D3.js saves you from having to write out numerous lines of SVG code manually to produce what you want. As a bonus, you can use the capabilities of an efficient programming language to manipulate your data, read and write to external files, get data from the Internet and so on. Consequently, D3.js enables you to produce SVG output without knowing SVG code, provided that you are already familiar with programming in JavaScript. However, if you really want to understand D3.js…

Although Swatch is limited in its abilities, it proves to be a very powerful tool to implement alongside other security products to proactively monitor system logs. The goal of a system administrator should be to run Swatch neither ‘too hot’ (alerting us to routine or trivial events) nor ‘too cold’ (never alerting us about anything). Swatch gives system administrators great log monitoring options; as a result, it’s a perfect tool for monitoring SSH or Denial-of-Service attacks on your Linux servers, possibly alerting you to trouble before it’s too late.…

One of the main reasons that the Raspberry Pi has been so popular in recent years is because it is an extremely capable little computer that packs a lot of punch for its very small price tag. Since the new release of the quad-core, BCM2836-based Raspberry Pi 2 Model B in the early months of 2015, it is now even more capable than ever before and makes the perfect platform for your very own low-powered, micro-sized home web server. In this tutorial we will show you how to set up a LAMP stack (Linux, Apache, MySQL and PHP) on your Raspberry Pi and then install a WordPress site on top of this. WordPress is one of the most popular content management and blogging platforms on the web, with over 52…

While the vcgencmd utility can get you information from the hardware of your Raspberry Pi, it isn’t the only way to do so. All of you experienced Linux users out there will be saying, “What about looking at /proc?”. For those of you who may be newer to this, all Linux environments have a part of the filesystem under the directory /proc. This subdirectory contains all sorts of information that the Linux kernel knows about. All of the information sources look like files to any programs you may wish to use. So for all of these, you can access the relevant information with a cat command. For example, you could get the CPU information with the following bit of code: You can also get memory information from /proc/ meminfo. This…

In an age when every piece of software seems to have become a web app with accompanying online signup to hoover up your contact details and preferences, it’s almost a novelty to return to a desktop app for help with your French homework. More than a desktop app too, Verbiste makes itself available to scripts, command line access and the inevitable Emacs interface. The commands french-conjugator and frenchdeconjugator are the scriptable interface. The grammar information and vocabulary can be found under /usr/share along with a template for a Greek version. Whether you’re studying French formally or improving your language ability for travel or business, verb conjugation is the area where beginner and intermediate users often fall down, leaving them sounding like officer Crabtree from the BBC sitcom ’Allo ’Allo! Pick…

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. Turn to page 83 to find his spreadsheet software group test and then over to page 90 for his FOSS reviews. Tam Hanna has been in the IT business since the days of the Palm IIIc. Serving as a journalist, tutor, speaker…

1 Google Drive integration The latest GNOME 3.18 release brings stable and reliable native integration with the Google Drive cloud storage service to Linux. Now baked directly into the file manager, there will be no need for users to install third-party applications or mess around with the hassle of synchronisation clients that can leave files orphaned. 2 Upgrade your firmware Through the Linux Vendor Firmware Service, it’s now possible to upgrade the firmware of a select and growing number of devices without relying on proprietary platforms. Support is also now built into GNOME’s software update system. 3 New calendar app Introduced as a preview in GNOME 3.16, the new calendar application integrates fully with GNOME 3 and offers support for GNOME Online Accounts (GOA), along with a familiar look and…

The Linux Foundation has announced the DiaMon Workgroup with the intention of creating a de facto standard for tracing and monitoring infrastructure to improve diagnostics of user-space programs. Founded by companies including EfficiOS, Freescale, Google, Hitachi, IBM, Intel, Netflix, Qualcomm, Red Hat and SUSE, the primary focus will be on improving the effectiveness of Linux performance testing tools by standardising interfaces and common exchange formats. “We hope that Linux Foundation workgroups can give the community a neutral place to advance Linux and collaborative technologies. The DiaMon workgroup is a perfect example of this by bringing community members together to advance work on an important area for Linux today and into the future,” claimed Linux Foundation executive director Jim Zemlin. “It is this collaborative work that sustains Linux’s success.” “When performance…

Let’s Encrypt, a free and automated certificate authority set up by the Electronic Frontier Foundation alongside companies including Akamai, Cisco and Mozilla, has passed a major milestone: the release of its first certificate. Founded following dissatisfaction with the high cost and complexity of traditional certificate authorities, Let’s Encrypt aims to offer trusted certificates at zero cost by automating the process. In doing so, its founders claim, it will encourage wider use of Transport Layer Security (TLS) cryptography across the Internet. “We’re thrilled to finally be a live CA,” claimed Let’s Encrypt’s Josh Aas of the certificate’s issuance. “We’ll be working towards general availability over the next couple of months by issuing certificates to domains participating in our beta program,” he added, admitting that it would be a month or more…

There are two programming environments to start with Currently, kids will be able to use one of two programming environments with their micro:bit. There is Microsoft Touch Develop, which is text-based and designed for use with touchscreen devices, with users following on-screen prompts and tapping through a virtual keyboard full of commands. The other is Microsoft Block Editor, a GUI-based environment that looks and functions a lot like Scratch, with users dragging around blocks of code that connect to each other. There are plans to also support a visual JavaScript editor called Code Kingdoms that enables users to switch between the text and visual editor views. Finally, there are also plans to support Python and there has been talk in some of the Python mailing lists of potentially supporting MicroPython…

Finally for this month, we have been intrigued by a paper recently published by Luis R. Rodriguez entitled ‘Increasing Automation in the Backporting of Linux Drivers Using Coccinelle’. Coccinelle is a semantic patching tool that can automate the process of screening kernel code for programming mistakes and can also be used (as in the context of this research paper) to perform transformations on kernel code, adapting automatically for changes in programming APIs and the like. Among others, Rodriguez maintains the Linux Backports project, which releases regular updated kernel drivers targeting older stable kernels that are in widespread use. In his paper (bit.ly/1N4It4m), Rodriguez proposes to automate much of this process of backporting using Coccinelle, which has many intriguing possibilities; for example, bringing new drivers to existing Linux distros and devices.…

Created by HP in 2007, FOSSology is an open source license compliance software project. It takes a software package and analyses each of its constituent files, using a heuristic pattern-matching algorithm to identify and report all of the software licenses. HP created it in order to quickly and accurately evaluate open source software that was proposed for use within the company, as well as software being considered for distribution. The company open-sourced the project to share its benefits with other organisations. FOSSology is used by companies ranging from Siemens to Intel’s Wind River in order to run license and copyright scans in one click, and generate Software Packet Data Exchange (SPDX) and Readme files with the copyright notices. In need of project hosting, asset ownership and project leadership, FOSSology investigated…

C++’s success is obvious, but object-oriented programming can also be achieved in C. Developers were quick to capitalise on its success and construct design patterns based on the structures, function pointers and other similar niceties. Vala is a C-based language that formalises these design patterns into language features in order to simplify their application. Its compiler transforms Vala code into normal C code that is then compiled using the system’s native compiler. In theory, Vala code can consequently be run on any C-based operating system – this statement, of course, ignores the availability of libraries. Compatibility is only one of the selling points here. Vala’s development was guided by the intention to create a language that was tied into GTK and its underlying GObject model – this was a difficult…

When creating a linked list or a similar data structure, developers tend to create data structures that are similar to the one below: class AnEvilObject:GLib.Object { public AnEvilObject prev; public AnEvilObject next; } While C# doesn’t have any problem with this object, Vala is not able to destroy two such objects that point to one another. This is caused by the reference counting principle: each of the objects has an ‘owner’ and can consequently not be removed. The example demonstrates this behaviour. Run it on a workstation of your choice for a closer look: public static int main(string[] args) { while(1==1) { AnEvilObject obA=new AnEvilObject(); AnEvilObject obB=new AnEvilObject(); obA.next=obB; obB.prev=obA; } return 0; } Fortunately, an easy solution exists. Declaring one of the two references as ‘weak’ informs the rubbish…

Resources Docker docker.com Deis deis.io It is a thing of the past to develop code and wait for the operations team to deploy it with your fingers crossed. DevOps is slowly gaining steam as the preferred mode of software development and deployment. DevOps methodology and its automation tools make it possible to deploy and test code in almost any kind of environment. Deis is one tool that lets you deploy a project written in any language or framework with a simple git push. You can also use Deis to promote existing Docker images through a continuous integration pipeline. Being a deployment tool, Deis integrates very well with Docker. All the applications you can deploy via Deis are distributed as Docker containers. Deis itself runs as a combination of several Docker…

Resources MonoDevelop monodevelop.com In the beginning, programs consisted of a group of functions that invoked one another. This led to a huge, state machinelike pattern, but as systems became more and more complex, cracks in this model started to show. Object-oriented programming, or OOP for short, seeks to alleviate this problem by basing itself on real-world structures. It takes only one look around you to see that the idea has merit: for example, a bottle of fruit juice has a lid and some contents. In essence, an object-oriented program’s core is but a ‘plumber’ creating, destroying and connecting instances of objects to one another in order to create the desired results. The individual elements are instances created from static blueprints known as classes. Developers benefit from OOP in a variety…

What you’ll need • Energenie IR module board bit.ly/1MdpFOU In this project you will learn how to emulate your television remote using your Raspberry Pi and a Energenie IR board in order to control your big screen. Why? So you can change the channel while no one is looking! Infrared, or IR for short, is light with a wavelength greater than the red end of the visible light spectrum, but less than that of microwaves. Infrared radiation can’t be seen with the naked eye, but it can be felt as heat energy. Infrared radiation is used to transmit data from device to device, including between remote controls and their televisions, Blu-Ray players or to provide data links over short distances between computers or mobile phones. This tutorial will show you…

All great games are based on blocks, fromTetris,throughBlokustoMinecraft. Tetris remains a favourite time waster for many, but for block lovers looking for a greater challenge, look beyond the square. Anupdateto Galois (notnamedaftertheFrench word for ‘Welsh’, but after Évariste Galois, a French mathematician and one of the founders of ‘group theory’) is an opportunity to once more look beyond the conventionalblock. Galois enablesachoicebetween regular blocks, three-dimensional shapes, hexagons and triangles. The latter provides a particularly pleasing set of shapes, reminiscent of tangram puzzles. Installation is easy from source, thanks to fairly minimal dependencies, and since the developer, Gerardo Ballabio, provides a deb package (as well as a Windows executable), Ubuntu and Mint users don’t even need to compile. On an Ubuntu Trusty box, we installed libxml++2.6-2 and ignored warnings about the…

Window Maker has just received its annual maintenance release, adding no new features – so why, you ask, would we want to know? Window Maker is the apotheosis of one branch of GUI-based interfaces. It is a window manager descended from pioneering NeXTSTEP computers of the late 1980s, on which both the first web browser (WorldWideWeb) and the first ever App store were both invented. The legacy of its widgets and icons influenceOSXtothisday,butitsreadilyaccessibleoptions make it a friendly user interface for GNU/Linux users from a non-Unix background. Window Maker is often grouped with minimal window managers as it lacks bloat and runs from minimal resources. However, it’s not a spartan environment and is easily expanded. Applications are reached through a right click to open the menu and any menu or submenu…

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…

Following its 2014 commitment to build a three-dimensional printer based on open source technologies, the modelling giant Autodesk has released the electronic designs and firmware source for its first attempt: Ember. Based around a modified version of the open-hardware BeagleBone Black microcontroller, the resin-based printer is now technically available for interested parties to modify and build themselves. However, Autodesk’s Eric Wilhelm has now admitted that it is unlikely to be just that easy in practice. “Fully opening the design of a precision tool as complicated as Ember is uncharted territory for us,” Wilhelm explained at the launch in September, “and we know this isn’t necessarily easy – Ember’s main electronics are a six-layer board and the design files are in the format of a professional tool. While it might also…

Richard Hillesley writes about art, music, digital rights, Linux and free software for a variety of publications Recently Christian Schaller, a Fedora and GNOME developer, called on The Apache Software Foundation (ASF) to admit that the Apache OpenOffice project is near its death and asks them to direct potential Apache OpenOffice users to the LibreOffice website. “Letting users believe that OpenOffice is still alive and evolving is only damaging the general reputation of open source Office software among nontechnical users,” he wrote, “and thus I truly believe that it would be in everyone’s interest to help the remaining OpenOffice users over to LibreOffice.” Both Apache OpenOffice and LibreOffice are derivatives of openoffice.org, a spin-off after Oracle purchased Sun Microsystems. The developers produced a fork of the code, LibreOffice, under the…

Top 10 This month Highlights openSUSE 42.1 Beta 1 Offering the first glimpse at an all-new look and feel, this beta offers a preview of the future of openSUSE, but not one that will be shared by the rolling-release Tumbleweed builds. Parsix GNU/Linux 8.0 The final release of Parsix 8 is a milestone for the project, marking its shift to Debian Jessie. Highlights include GNOME 3.16, the Linux 4.1 kernel tree and official UEFI support. Peppermint OS 6 While the latest Peppermint OS respin doesn’t change anything fundamental, it brings full support for Secure Boot, UEFI and GPT systems for the first time, consequently dramatically improving its compatibility. Latest distros available: filesilo.co.uk…

Mihalis Tsoukalos is a UNIX administrator, a programmer, a DBA and a mathematician. He has used Linux since 1993 “The problem that will be examined here is the following: given a function that produces a random integer in the range of 1 to 5, write a function that produces a random integer in the range of 1 to 7. This article will give you some ideas on how to approach this simple problem, but it will also show you that there is no single or perfect solution. Solving the problem the other way around is a lot easier and simpler because you can use the modulo operator to do your job or just ignore the output that you do not want. The random numbers for mimicking the initial function will…

A new battery pack has pushed the micro:bit delivery back to 2016 Due to changes made to the power supply of the micro:bit, distribution of the microcomputers to schools has been delayed to next year. Initially, the micro:bit was to be powered by a watch battery for use when not tethered to a PC or laptop, but a couple of months ago it was announced that the micro:bit would now be powered by two AAA batteries, connected via an external battery pack. As a result, the knock-on delays have led to the micro:bit missing its deadline for the start of the 2015/2016 school year. The plan is now to have them sent to teachers before Christmas, so that they can familiarise themselves with the devices and learning materials ready for…

The Linux Foundation’s OpenChain Workgroup is a community effort to standardise common best practises and ease open source compliance for companies and developers. It is expected to reduce costs and the duplication of efforts as well as ease the friction points in the software supply chain. As Jim put it, “Because nearly every new technology today is built using Linux and open source software, today’s software supply chain is the open source software supply chain. This means we need to revisit the way we standardise processes and compliance for checking code and ensure the cost and efficiency benefits of open source are sustained for decades to come.” What this means is that the OpenChain Workgroup will work to provide a baseline process that can then be customised as companies and…

On Ubuntu, the latest version of Vala can be downloaded via apt-get if the repository list is first expanded. Run: Due to compatibility reasons, the default vala and libgee packages provide outdated versions. Visit bit.ly/1Fl0V69 in order to find the names of the most current editions; at the time of writing, the correct install command is: Libgee is a package that provides easy access to a variety of storage classes. The Vala language specification intentionally excluded storage classes and similar trinkets for simplicity – this is because it would be pointless to reinvent them as they can already be found in GObject. Deploying our GUI-based examples on an Ubuntu system also requires the installation of the GTK+ GUI stack and its development support files:…

Resources Text editor GCC compiler This article will talk about the system calls that should help you perform basic file I/O in Linux. It would be very beneficial to revisit this article after reading it for the first time in order to truly understand the information presented here. Some things may look simple yet they might turn out to be more difficult on reflection. As usually happens with practical subjects, the more C code you write, the more you will understand the techniques as well as the theory behind the practice. The good news with file I/O is that there are just five system calls alone that have the ability to program most of the file input/output functionality on a Linux system: read, write, open, close and lseek. There are…

Resources Text editor MySQL database Regular expressions are a central part of modern computing and are supported by all programming languages in one way or another. An example of a simple problem that can easily be solved with the use of regular expressions is converting the first letter of the first word found in each line of a text file to upper case. This tutorial will discuss Turing machines, finite-state machines, automata and grammars, because they are the building blocks of regular expressions. We will also briefly cover the required theory, because it would be impossible to fully understand regular expressions without knowing the necessary theory behind the practice. However, as regular expressions are a practical subject, you should spend some time experimenting on your own as well, even if…

What have you done with your Raspberry Pi camera lately? While it gives us plenty of new ways to use the Pi, unless you’ve got your computer set up as a security webcam or you’re particularly a fan of time-lapse photography, the chances are that you’ve overlooked the Pi camera module for a while. If you’re a fan of animation or you simply want to extend the possibilities of the module, why not build a stop-motion camera? By using Python and an external button to capture images, the Raspberry Pi can be the perfect tool for animators. Better still, you can go beyond animating toys or bits of LEGO and go old school by mounting the Pi on a rostrum and creating a cartoon. Even if you can’t buy or…

Why Python? It’s the official language of the Raspberry Pi. Read the docs at python.org/doc In previous articles, we have looked at how you can use your Raspberry Pi in order to monitor the environment around itself. However, we haven’t looked at how the Raspberry Pi can monitor and see what is happening within itself. Luckily, Broadcom have included a command line utility, named vcgencmd, that is designed to deliver to you exactly that type of information. You can get a full list of the commands available with the command vcgencmd commands. Currently, the most complete documentation is available from the website elinux.org/ RPI_vcgencmd_usage, but there is no official documentation available at the time of writing this column. The first step is to take a look at using the vcgencmd…

From Snowden information on government bulk surveillance, to worriesoverhowourprivateinformation is harvested by communications companies and social networks, there are many good reasons to protect your email with encryption. GnuPG (the GNU Privacy Guard) can be used to encrypt data for storage and also to create digital signatures. It includes a key management facility and is compatible with the OpenPGP standard, RFC 4880, but it doesn’t use patented algorithms. This new version provides support for Elliptic Curve Cryptography (ECC) for a smaller key size; a 256-bit ECC public key provides comparable security to a 3072-bit RSA public key. No matter how great GnuPG is, it has no benefit if it’s not used, so the Free Software Foundation has a great guide at emailselfdefense.fsf.org to help get you started. Follow the guide…

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