Linux User & DeveloperNo. 164的目錄

This issue » Discover 25 projects made possible with Pi 3 » Test out the next generation of distros » Create a simple programming language » Set up a DNS proxy and Tor router Welcome to the latest issue of Linux User & Developer, the UK and America’s favourite Linux and open source magazine. Change is upon us! Wi-Fi and Bluetooth modules finally came within reach of the Raspberry Pi Foundation’s $35 price point for the Model B, so the recently released Pi 3 ships with excellent wireless capabilities – not to mention a 1.2 GHz, 64-bit quad-core ARM CPU. James Adams, the Foundation’s director of hardware, explains all from page 18. Turn to page 22 to find the projects we’ve come up with, and see page 26 for Gareth…

1 Multi-window mode One of the most hotly anticipated features of N is its new multi-window mode. With this enabled, users can seamlessly switch between multiple apps in seconds, or when needed, use multiple apps simultaneously. 2 Interactive notifications In a move that closely resembles iOS, N users will now be able to reply to messages directly from their notification panel. A quick overview of the message will be shown with users needing to simply double tap on it to start a reply. You’ll never need the Messaging app again! 3 Souped-up settings An overarching system menu has been implemented to help get around the Settings app at a much quicker pace. No matter what menu you’re in, a press of the recognisable menu icon will show a overview of…

“The most popular way for gaming enthusiasts to emulate and enjoy retro titles” After nearly two decades of availability, MAME (Multiple Arcade Machine Emulator) has finally made its transition across to open source availability. Previously the software was available under a BSD licence, which prohibited any sort of commercial use of MAME. Despite the legal grey areas that MAME has had to deal with in its lifespan, it still remains far and away the most popular way for gaming enthusiasts to emulate and enjoy retro titles from yesteryear. Up until recently, the source code for the MAME software had been readily available, but heavy restrictions were in place to limit what outside users were able to do it. Users can now modify and distribute MAME to their heart’s content. It’ll…

Microsoft’s much-rumoured ventures into open source software have been made clearer after its official announcement that its popular SQL Server will be made fully available on Linux desktops. In a report published by Microsoft’s Executive VP, Cloud and Enterprise Group, Scott Guthrie, SQL Server capabilities on Linux will “deliver a consistent data platform across Windows servers and Linux, as well as on-premises and cloud. SQL Server on Linux will provide customers with even more flexibility in their data solution.” Linux users will have the complete suite of SQL Server features available to them by default, including the likes of Stretch Database, which acts as a low-cost solution for customers to access their data whenever they need to. The announcement will now mean that developers can now build applications based around…

There’s a myriad of ways that users can encrypt their web life, and most don’t require much work or outlay on the user end. VPNs have always been touted as the easiest way to stay safe online – not only do they add an extra layer of security to your network, it’s also an invaluable tool for protecting your privacy. Also, consider the browser you use; while Firefox is undoubtedly an encryption-friendly choice to make, the likes of Tor also come highly recommended. Through its additional software, Tor is capable of relaying your web traffic through several other computers before arriving back at its destination.…

“Contemporary Linux isn’t strictly formed from a single inseparable, inviolable whole” Linus Torvalds announced the final release of Linux 4.5, noting that he “just couldn’t make up my mind whether I should do another rc8 [release candidate] or not, and kept just waffling about it. In the end, I obviously decided not to, but it could have gone either way.” As we reported in last month’s issue, the latest kernel includes fewer earth-shattering new features than are true of a typical release cycle (this just happens periodically during the year based upon when certain new features are developed and available) but it does have among the new features support for volatile memory ranges via madvise(), which we covered in detail in last issue, as well as an important copy offload…

The conformance testing involved radiated and conducted modes. With the latter, “rather than pumping it into the aerial and spraying the RF into the air,” James explains, “you plug a cable into the tester. For that, you need to have some kind of connector on it. There’s a tiny shorting resistor you connect to the U.FL connector, and you can then connect an antenna or, in our case, all the test equipment we needed. I would say that if you want to use the U.FL antenna, don’t – the FCC don’t like it. But, theoretically, you could scrape the soldering mask off, solder a U.FL on, and connect an antenna.”…

As Linux users, we’re pretty fortunate when it comes to being able to switch up our desktop experience whenever we see fit. The process of switching between distros has never been easier and, thanks to the likes of VirtualBox, testing out potential distros can also be completed in a matter of minutes. But despite the increased amount of choice in distros and the simplicity of switching between them, many Linux users still rely on the traditional powerhouses for their needs. The likes of Ubuntu, Linux Mint and Debian have long been recognised as one of the primary reasons for the year-on-year increase in Linux users around the world, offering accessibility to the OS for those making the transition from Windows and OS X. However, the next generation of Linux distros…

You can do many things with Go, including the implementation of the techniques discussed in this tutorial. The advIO.go code shows how to perform memory mapped File I/O in Go. The program requires the “unsafe” Go package because it recasts pointers – this means that if you do not handle pointers correctly, it will crash. On the other hand, if you do handle pointers properly, your programs will run fast. The most interesting part of advIO.go is the following because it is where the mapping takes place: The full Go code of advIO.go can be found in your resources pack. If you run it, you are going to get the following output, which is what is going to be written to the binary file:…

Resources Dnsmasq bit.ly/1XAorA4 Haproxy haproxy.org Using VPN software enables you to have a completely different public IP address and region, which matches with the VPN server. This technique works but it does have significant disadvantages: your internet connection is now likely to be slow because everything is now going through the VPN server. It is also difficult to deploy VPN, as the client may need to support the VPN protocol used, and some devices do not support VPN in the same way as things like Android TV, the PS4, the Xbox One, etc. The solution to all of these problems is a DNS proxy server. It only redirects selected traffic so it does not affect the rest of the internet connection, and its deployment is also as easy as changing…

A regular grammar is a set of production rules for strings in a formal language. The production rules describe how to create strings from the alphabet of the language that are valid according to the fixed syntax of the language. A grammar does not describe the meaning of a string or what can be done with it in whatever context – only its form. Each regular grammar describes a regular language. Therefore, you cannot define a programming language without a properly defined regular grammar.…

The actual drawing commands consist of telling OpenGL where the vertices are located within the window Why Python? It’s the official language of the Raspberry Pi. Read the docs at python.org/doc “Many of the examples we have looked at in this column have been programs that run on the console. This month, we will be taking a look at how you can include 3D graphics within your Python code. The hardware on the board includes a GPU, so you should be able to take advantage of everything this computer is capable of. Since we are going to be playing with graphics, this means that you will probably want to have an actual monitor connected to your Raspberry Pi. If you don’t have one, you can connect to your Raspberry Pi…

What you’ll need Ethernet cable Wireless router USB WiFi adaptor or Raspberry Pi 3 Are you concerned about your online privacy? Suspect that the NSA or GCHQ are tracking you online? Or are you simply anxious about advertising networks targeting their ads at you? If this is the case, or you’re simply on the lookout for a new project, then setting your Raspberry Pi up as an anonymising Tor wireless access point is a good way to save time and effort setting up Tor on all of your PCs and mobile devices. If you’re unaware, Tor is free software that enables anonymity online and routes internet traffic through a worldwide anonymising network of over 7000 relays. By doing this, your location and website use can be concealed from techniques such…

FFmpeg provides transcoding libraries – libavcodec, libavutil, libavformat, libavfilter, libavdevice, libswscale and libswresample – used by VLC, Xine, getiplayer, Handbrake, and for multimedia playing within Firefox. It’s also a suite of useful command line tools, including ffmpeg, a fast audio and video converter; ffplay, a simple media player; ffserver, a streaming server which can forward ffmpeg streams, or stream directly from disk; and ffprobe, a useful tool for gathering information from streams – either directly (the output is “human-readable”), or for use in monitoring scripts. The FFmpeg project is dedicated to giving users the best encoders – shipping external encoder libraries where their own are not yet mature, and offering internal and external where there is no obvious “best choice”. Until recently ffmpeg has included the VisualOn AAC encoder (libvo-aacenc),…

“Software Freedom Conservancy and their lawyers are unequivocal in their belief that Canonical’s inclusion of ZFS in an Ubuntu distribution is non-compliant with the terms of the GPL” Canonical’s decision to include ZFS in Ubuntu 16.04 LTS has become the source of some controversy. ZFS is the open source File System and Logical Volume Manager introduced with OpenSolaris in late 2005, and was released under Sun Microsystem’s Common Development and Distribution License (CDDL), which the Free Software Foundation has always described as incompatible with the GPLv2, thus rendering ZFS inaccessible to GNU/Linux. Until its purchase by Oracle, Sun Microsystems had a considerable history as a contributor and beneficiary of open source projects. Bill Joy, the prime architect of SunOS and Solaris, was the lead developer of BSD Unix, and wrote…

Top 10 (Average hits per day, 19 February – 16 March) This month PCLinuxOS hits the top ten at the expense of Android x-86, which has faded down the table after a sub-par month in downloads Highlights Red Hat 6.8 Beta The new RHEL beta gives customers a chance to preview some of the new features, including the likes of Relax-and-Recover archiving and the newly implemented Libreswan VPN software. Manjaro Manjaro now provides a completely new graphical interface, making it easier than ever to install and remove the many kernels they offer. Its selection of kernels is unrivalled by its competition. Untangle NG There’s a new look to Untangle’s firewall service, making it easier for new users to customise their desktop for security. No core features have been altered, so…

“Even if you define a C string using an array, the C string can be accessed using pointers and vice versa” The strlen() function finds the length of a string by counting the number of characters that precede the terminating NUL character Every C string is required to be stored in this way; if there is no terminating character, C cannot determine where a string ends – a nasty bug that the compiler cannot detect! The most important thing to remember is that a string in C is terminated with the ‘\0’ character. Do not get confused; in C, ‘\0’ is a single character despite the fact that it needs two characters to get printed on your screen. As always, there are two ways to deal with strings in C:…

Mozilla’s The Web We Want campaign is all about getting into the cold, hard facts about how people use the web and want they want from it. It’s a great tool to help view which parts of the world care most about privacy, or learn about the most important issues that affect millions of internet users every day. But it goes even further than that; users can partner up different countries to compare usage statistics and see how different their web problems are. Mozilla’s ambitions for a free, neutral and easily accessible internet has never been made clearer than here.…

WHAT ARE THE BIG CHANGES? A lot of the Raspberry Pi 3 is the same as the Raspberry Pi 2. Our strategy for the Pis from the B+ has been to try and keep the same form factor. The B+ was really the first Pi that I worked on when I came to Raspberry Pi in 2013, and the idea was that we’ve got this nice form factor and we want to keep it, so to build the Pi 3 I took the Pi 2 design and literally just added the extra stuff. So, we’ve got the new processor courtesy of Broadcom – they’ve done a nice uplift. It’s similar to the BCM2836; the Cortex A7 was taken out and the A53s were put in, and everything else has actually…

1 WILDLIFE CAMERA Parts – Waterproof case with a camera mount – Portable power pack – Camera module – PIR sensor – Real-time clock While you can pick up a kit for this, like the one from Naturebytes (bit.ly/1PdUNue), it’s easy to put your own wildlife camera together. Make sure that you have a waterproof case to protect your Pi, the portable power supply and your other electrical components against any damage from rainwater; there are 3D models (STL files) available, which you can easily tweak to fit the Pi 3 using a simple program like 123D Design. Then you just need to use waterproof sealing on any joints and on the hole through which the camera module points – check out this guide: bit.ly/1mgUA2X. You can set your Pi…

Resources Text editor GCC compiler Go compiler Rust compiler Perl interpreter Advanced file I/O means that you can do all usual file I/O operations with extra powers such as record locking, nonblocking I/O, I/O multiplexing, asynchronous I/O, memory mapped I/O, and scatter read and gather write. Don’t worry; we will take you through everything you need to get started. This tutorial will present the system calls and explain the techniques that will allow you to perform advanced file I/O; it will be the most challenging subject you have seen in the Systems Programming series. Most of the code in this article will be written in C but you will also see examples in Go, Perl and Rust. Please bear in mind that the concepts and principles of advanced file I/O…

Resources Hadoop bit.ly/20m1Z3h HBase hbase.apache.org Eclipse eclipse.org Big data – measured in terabytes/petabytes – cannot be stored and processed with traditional databases, so it was only a matter of time before something like Hadoop came into existence. Hadoop uses HDFS (Hadoop-distributed file system) and MapReduce to store and manipulate this data. But the problem with Hadoop was that it is only applicable for batch processing. For real-time read/write access to very large data sets, HBase emerged. HBase is an open source, column-oriented database built on top of HDFS. The HBase project was started by Chad Wand and Jim Kellerman at Powerset and was modelled after Google’s Big Table. HBase is well suited for sparse data sets, which are very common in big data. Moreover, it provides APIs that enable development…

Resources Mattermost mattermost.org Communication is a very important aspect of team dynamics. The productivity of a team depends on the quality of communication that people in the team have with each other. There has to be a balanced approach where the team members, while sharing a great rapport, do not invade the personal space of others. While a lot of this depends on the individuals themselves, or the company culture, the tools that you use have a very important role to play too. In this tutorial, we’ll take a look at Mattermost, a tool that can help you streamline and simplify your team’s internal communication, while being hosted behind your own firewall. Not only this, it also integrates well with other software like Jenkins, GitLab, SVN, etc to give a…

Make is a powerful build automation tool. Makefiles are the configuration files of GNU make, which is the standard implementation of make for Linux, and they help you organise and group various commands and execute them with a single make command. The Makefile we made to support this project involves the execution of one of the following commands: The “make clean” rule is pretty simple because it just deletes everything the other steps produced – as you may have guessed, neither myCalc.l nor myCalc.y will be deleted. The “make myCalc” generates the executable file whereas the other two commands generate myCalc.tab.c, myCalc.tab.h and lex.yy.c.…

“But, what about 3D?” we hear you ask. Luckily, we can reuse much of what we have already covered here to move into three dimensions. The first change is that vertices now are defined with three values rather than two, giving you a set of x, y and z coordinates. The second change is in the category of functions that you need to use. You can see that the drawing functions used are explicitly two-dimensional in their names. For example, you should have noticed the ‘2’ in names like ‘glVertex2f()’. To draw three-dimensionally, this changes to names like ‘glVertex3fv()’. The third change is more conceptual. Once we move to three dimensions, we need to worry about where we are in relation to the object that is being drawn, and what…

Putting circuits together can be tricky, even for experts. Fortunately, various notations exist that make it easier to work out just where wires, components and power sources are connected. But rather than jot these details down with a pencil and paper, you might prefer to bring an element of realism to the illustration. This is particularly useful for beginners, and if you’re demonstrating a breadboard-mounted circuit with an Arduino, for instance, you might wish to clearly and accurately illustrate the precise positions of each component and wire. This is where Fritzing comes in. You’ve probably seen illustrations of circuits in the pages of Linux User & Developer over the years, and with Fritzing you too can put together circuit illustrations, simply by dragging and dropping the categorised components into place,…

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…

Facebook’s Open Compute Project has been picking up a lot of steam as of late, and the acquisition of Google shows its momentum. The project was originally created six years ago for end-user companies to collaborate on data centre equipment, as a way of keeping costs down and free of superfluous features. While a number of other technology giants have already jumped on board with the project, including the likes of Microsoft, Google has long been absent from the list until the recent OCP Summit in Silicon Valley. Google is already touted for owning some of the world’s most advanced data centres, and its first contribution will be to produce a new rack design that powers servers with an enhanced 48-volt current, compared to the standard 12 volts used in…

It seems like only yesterday that we were looking at the 5.1.0 release of the ever-popular LibreOffice suite, but the team behind it has recently announced the first point update for the 5.0 series. “The Document Foundation releases LibreOffice 5.1.1, the first minor release of the LibreOffice 5.1 family,” said Italo Vignoli. “The latest update is targeted at technology enthusiasts, early adopters and power users.” While the latest update mainly irons out many of the bugs that troubled the previous instalment, there are also a number of new features worth getting excited about. The software now has vastly deeper integration with cloud servers, enabling users to not only read documents stored in accounts, but also make subsequent edits to them. Transitions to the cloud seem generally quicker and easier to…

Could you tell us the key principles of the encryption campaign that Mozilla is launching? Ultimately, we set out to create an education campaign. We want to make public understanding of encryption more mainstream and easily recognisable for people all over the world. When you then get more people involved, it’s easier to get people to understand and get involved with the concepts around encryption. It’s a term that many people would have heard of, but understanding what it means for them is a whole other concept. Mozilla wholeheartedly believes encryption is key to a healthy internet. It’s a crucial part of both online security and privacy at the most basic of levels and it allows us to more safely bank, shop and communicate online. Encryption plays a big part…

The Let’s Encrypt project is a certificate authority aimed at making encrypted connections to the web as ubiquitous as possible, ultimately lowering the complexity of setting up TLS encryption. The primary benefit of the Let’s Encrypt authority is that it provides the necessary framework for companies to automatically obtain a browser-trusted certificate, but without any human intervention. There’s no configuration editing or validation emails, or any prospect of expired certificates taking your site offline, thanks to auto-renewal. We should also mention it’s completely free – a giant step in a new direction for website security. As far as Linux Foundation collaborative projects go, this is one of the best ones that will be of benefit to millions of site owners the world over. See letsencrypt.org for more info.…

There’s been speculation that the Pi 3 boasts an FM receiver, but this is sadly not the case. “The FM is effectively disabled,” confirms James. “The Wi-Fi chip is a BGA device, so underneath you’ve got tiny bumps of solder and they have to solder onto the PCB. Now, on that chip they are pitched 0.4mm apart, which is actually designed for higher-tech mobile phone PCBs – higher-tech than the board that the Pi uses. One of the reasons we got the cost down is because we use low-tech PCB design, so actually, through some clever tricks, we’ve managed to use that higher-tech part on the lower-tech board, but at the expense of FM – too many signals to route out, and you have to resort to a higher-tech PCB.”…

The main disadvantage of all advanced file I/O techniques is that they need additional code, which means that you might create more bugs; other than this there are only advantages. What is really important is deciding whether the extra effort can be justified by the benefits they might bring. The key here is to compare the speed of normal file I/O with the speed of an application that uses an advanced technique before deciding. It is expected that you might never use some of them; memory mapped I/O is a specialised technique that can be used for dealing with the shared memory of related processes, but might not be appropriate for reliably and quickly copying a binary file. Another thing you must consider is that most of the time you…

Resources MonoGame monogame.net Shaders let you run code on a massively parallel computer system: even the most primitive of GPUs bring along at least sixteen cores, along with a substantial amount of really fast RAM. In fact, for most computers, the GPU provides significantly more raw computational power than the CPU. Transferring processing workload to the GPU can lead to significant performance improvements. In the last few years, shader use has been expanded from traditional rendering. Textures play a key role in such applications: they provide the only truly efficient way to pass data into and out of the GPU. At the end of the previous article, we presented a little coding challenge to the willing reader. Applying post-processing effects to the results of a rendering process requires that said…

Resources Text editorGCC compileryaccflexlexbisonGNU make This tutorial will present the necessary knowledge and code that you need to know in order to create a programming language. The programming language that is going to be developed will emulate the functionality of a simple integer calculator; it might seem strange at first but a calculator is implemented using a simple programming language. You can better understand this if you realise that the “---1” string is not supported by any ordinary calculator, which means that it does not belong to the language of the calculator. The presented example will be implemented in C with the help of some truly sophisticated UNIX command line tools. The main benefit you get from using language development tools is that they allow you to concentrate on what…

Like it? Niels has uploaded a series of YouTube videos depicting the original testing of the ROV, as well as how it performed in open water conditions. Check out his channel: youtube.com/user/ gravitylost1 Further reading Niels took a lot of inspiration from the OpenROV team, who have been producing underwater exploration vehicles for a number of years. Take a closer look at what they do over at www.openrov.com Why did you decide to build an ROV (remotely operated vehicle)? When I was a kid I frequently built RC models; sailing boats and speedboats. While I owned a fantastic RC glider and dreamed of having my own RC submarine someday, my neighbour at the time had an RC submarine and discouraged me from building one by saying this thing always had trouble…

What you’ll need Raspberry Pi Sense HAT Last November, two Raspberry Pi computers were each fitted with an Astro Pi, which is an add-on board boasting an array of sensors and an 8x8 LED matrix. These were flown to the ISS and delivered to Major Tim Peake with a selection of school children’s experiments. In late December, the Astro Pi was released for sale to the public as the rebranded ‘Sense HAT’. This consists of exactly the same hardware and sensors set found on the Astro Pi but with a new ‘Sense HAT’ API. The first part of this two-part tutorial introduces you to the Sense HAT hardware and walks you through the skills required to create a Sense HAT version of the updated classic Rock, Paper, Scissors, Lizard, Spock…

Backup solutions range from simple, home-brew, rsync-based scripts, to glossy commercial software, which is often just a fancy front-end to rsync-based scripts. It’s essential to make backups, even if only a regular cp -a, because one day you will need to recover data. The fact that so many people don’t do regular backups is in part, no doubt, owing to user inertia, but the complexity of the task, and the perceived failings of backup solutions – particularly the software’s interface – takes some of the blame. Tardis aims to be a step up from rsync-based scripts, but no more complicated than is needed. Reasonably easy to start working with, but fairly powerful and configurable, it’s inspired by Time Machine, and provides encrypted and incremental backups (and revision-like access to the…

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