Linux User & DeveloperNo. 183的目錄

Welcome to the UK and North America’s favourite Linux and FOSS magazine. Even by our standards, this issue is packed to the rafters! Purism hit the headlines with its Librem 5 phone (p6), and we’ve interviewed CEO, Todd Weaver (p50). Next up, we collared Richard Brown to explain openSUSE’s container-as-a-platform plans and respond to the Btrfs hate (p12). We also decided it was time someone extolled the virtues of Arduino given that the dust has finally settled over its ownership (p56). Of course, to complement all that, we have our usual slab of tutorials and regulars starting on p36. This issue, we have a new series called InspiringOS (p32), where we highlight open source projects and people who are attempting to change the world. The origin of the word ‘inspire’…

1 Audacity Probably the default choice for most Linux users, Audacity can do everything from recording and editing multi-track music to picking up audio from online radio. Ideal for editing podcasts and other voice work, Audacity can be given extra functionality, effects, and import/output options with community-developed plug-ins. 2 Ardour Capable of recording, editing, and mixing, Ardour (http://ardour.org) is intended for musicians, composers and soundtrack editors, and supports hundreds of plug-ins. Available in two ways: a one-off payment or subscription for the packaged version, or a free, compile-it-yourself option. 3 LMMS Download LMMS for free at https://lmms.io, where the purpose is to make music now. With 19 built-in instruments, advanced routing, unlimited tracks and arbitrary effects support, LMMS has versions for most key distros, and VST support via Wine. 4…

It turns out that saying goodbye to Flash might not be all that good after all. After years of being the web’s whipping boy, Adobe Flash’s (and Shockwave’s) impending demise in 2020 is coming around a bit too soon for some. The reason is simple: history. As an important part of the web’s first two decades, Adobe Flash was the multimedia platform. Its use goes beyond playing pop videos and movie trailers; Flash and Shockwave were used for artistic expression. So with a vast archive of old-but-live websites requiring Flash, a solution is needed to keep them running beyond 2020. And it’s a pretty simple solution: but will Adobe agree to open-source Flash? If it doesn’t, there are at least a couple of solutions waiting in the wings. The first…

“It makes sense to try alternative options, even if you don’t end up switching – it’s good to have a view of what else is happening out there in the Linux world” There are no definitive metrics, but anecdotal evidence suggests that Linux users have a tendency to start with a particular distro and stick with it regardless of what they are doing and how the Linux scene progresses. It makes sense: we all get familiar with our chosen environment and the more we use it, the more effective we become at achieving what we set out to do. The same applies when it comes to not just the distro itself, but the open source software we use on top of it. The Linux world offers a wealth of options…

Choosing a Linux distribution for enterprise is less about features and more about support. Linux is already a powerhouse in the enterprise server market and has a steadily growing footprint on the desktop, but an operating system powering your business has to be utterly dependable in all kinds of scenarios – few firms in the Linux space are better placed to deliver that reassurance than Red Hat. Products from the company are used by over 90 per cent of Fortune 500 companies. The Red Hat Enterprise Linux (RHEL) life-cycle is quite different to other distros – version 7 was first released in 2014 while 7.4 (also known as 7 update 4) was released in August 2017. Minor version updates are typically released every 18 to 36 months, with support provided…

With great power comes great responsibility. And great potential for things going wrong. Now and again, even the most experienced of Linux users comes unstuck, ending up with a system that goes wrong, won’t boot, has an issue and needs some urgent repair. More often than not it’s Windows doing something nasty to GRUB, but when that situation happens, you need something in your armoury to get you out of trouble. That’s where repair distros come in. Typically launched from USB or DVD but also installable to a dedicated partition of your hard drive, repair distros are designed to have all the tools to hand that you need to get back up and running in a crisis. One great example of the genre is SystemRescueCD – a one-stop distro for…

We all know Linux best from our desktop and server experiences, but the OS is also in use across the world tailored for very specific tasks. This approach can be applied in your home too, by using the excellent OpenELEC distro for your home entertainment needs. OpenELEC is designed to turn your blank PC into a fully featured media machine in less than 15 minutes. Enjoyed by over 450,000 regular users, the award-winning platform runs well on a wide variety of hardware (including the Raspberry Pi and a number of other ARM-based platforms), uses barely 100MB of disk space and can run from hard disks, SSDs, CompactFlash or SD cards. 32-bit builds were deprecated last year, however, which slightly limits the machines that can support the distribution. Media content is…

Android is a dangerous ecosystem indeed. Even when you are installing apps from the Google Play Store, there is still a chance you can harm your smartphone with a potentially harmful app (PHA). That’s why it is so important to learn a few tricks. Android apps are mainly written in Java. Some may include native libraries (.so) and executables (ELF) too. An APK is merely a ZIP file containing a DEX binary that will be parsed and then executed by the Dalvik or ART runtime engines, depending on the Android version. It also includes additional files such as bitmaps, XML GUI layouts and so on. The DEX bytecode can be formatted to be human-readable using open-source tools, giving us smali. Debugging smali is easier than native code. While under some…

01 Prepare your Arduino Mount the Ethernet shield by inserting the shield pins into the Arduino headers. Connect a USB to your computer and an Ethernet cable to your router. 02 Connect the sensor Attach the temperature sensor to your breadboard. Using the data sheet for your sensor, connect ground to GND, IN to a digital output, and OUT to an analogue input. 03 Write a sketch Create a new sketch and initialise the pins as wired in the previous step. Set the digital output pin to HIGH and in ‘loop’ read from the analogue input pin. 04 Convert to temperature Refer back to the data sheet. You’ll need to apply some maths to the Arduino input (0 to 1024, which maps to 0 to 5V) to turn voltage into…

We’ve looked at how to handle parallel tasks strictly within a Python program. But sometimes you need to run other pieces of code asynchronously. In these cases, you can use the subprocess module to execute external code and interact with it. As an example, we will look at how you could run the ls program and use its output. The run method accepts as input the external program to be run, along with any parameters. By default, run doesn’t send the output from the external program back in to the main Python code. In this example, we set the input parameter stdout to be the PIPE value, so the output from the external program is sent back to the calling Python code. Sometimes, you may want to run this external…

A fifth of the web runs on WordPress (WP) and it’s a great content management system. But if you just want a good-looking blog, without the distractions, you need something closer to what WP was ten years ago. Ghost was created to be just that. It’s always nice when something based on JS works so smoothly, particularly as most of it is developed under macOS, and not your distro. If you’re setting up a production server, advice on when to use or not use sudo with npm, for example, will be different for Debian from the advice given in many READMEs that are aimed at other platforms, but running a local install for trying out Ghost should be painless on any platform – and certainly was for us. First impressions…

It’s most likely you’ve written at least some Markdown, perhaps a README.md file for a GitHub page. But have you looked at what lies beneath? Ambiguities in the original Markdown spec, and bugs in the reference Markdown.pl implementation led to an effort to standardise Markdown in 2012, and this app is the reference implementation. If you only have to convert a few documents from Markdown to HTML, then you won’t necessarily mind a few milliseconds here and there in the conversion process, and will use Pandoc, or whatever tool you have to hand. If you have a static blog, you’ll be using its built-in tools. But if you have a substantial set of documents – particularly one under constant revision – then CommonMark.c’s speed is reason enough to give it…

“Most notable are the improvements to Chromium (v60), enabling the browser to run faster” Following the launch of Debian Stretch, Raspberry Pi users can now get hold of Raspbian Stretch, the dedicated distro from the Raspberry Pi Foundation. Still wielding the PIXEL desktop, Raspbian Stretch comes with a number of improvements, described on the Raspberry Pi blog: “The differences between Jessie and Stretch are mostly under-the-hood optimisations, and you really shouldn’t notice any differences in day-to-day use of the desktop and applications.” Most notable are the improvements to Chromium (v60), which include improved memory usage and efficient code, enabling the browser to run faster. There’s also a tweak to the browser’s appearance. Regular users of Sonic Pi, meanwhile, will notice some additions to input and output, including MIDI and OSC.…

Following a successful IndieGoGo campaign in which the $200,000 goal was surpassed by 1,516%, Chinese hardware producer GPD has begun shipping its ultraportable PC. Packing a 64-bit quad-core Atom CPU, 8GB of RAM and 128GB of storage, its eight-hour battery is charged via a USB Type-C port. The keyboard is as large as is practical, while the touchpad is replaced with a nipple-style controller. The GPD Pocket Ubuntu Edition is just 180×106mm, and an impressive 18.5mm thick. Slightly thicker than a 7-inch tablet, it boasts a 1,920x1,200 pixel IPS touchscreen display. However, GPD is pitching it to a totally different market. “This pocket laptop adopts [a] pure silver CNC precise all-in-one body made of magnesium and alloy, which means that its craftsmanship can be comparable to the MacBook Air.” Essentially…

It’s a good time to interview SUSE and explore the latest developments in openSUSE, as SUSE celebrates 25 years this month. The company has gone from releasing an extended version of Slackware to building its own distro, SUSE Linux Enterprise (SLES), but it was 2004 when the firm announced the community-run openSUSE project, which has fuelled SLES development ever since and seen the rise of both the Tumbleweed rolling-release distro and its solid, regularly released Leap distro. However, for this interview we were mostly concerned with asking Richard Brown, the chairman of openSUSE, about Kubic, a community-driven container-as-a-service platform that includes MicroOS, SUSE’s take on cluster computing for containers and microservices. SUSE celebrates 25 years this month, what are the key moments in SUSE’s history that the whole GNU/Linux community…

Ubuntu is the undisputed heavyweight in today’s Linux market as the most widely used consumer distro, with a strong and growing presence in enterprise. This market-leading position is justified – for the majority of users, it is simply the best choice. Aside from the fact that the Debian-based distro is stable, frequently updated, polished and an intuitive switch for new Linux users, a key benefit of choosing Ubuntu is the vast amount of community support out there should you have any issues. If you come across a problem, there’s a good chance someone will be able to help you out. The default Unity desktop environment is intuitive yet powerful and flexible, and early previews of the forthcoming GNOME move (Ubuntu owner Canonical is discontinuing Unity) indicate that this is set…

A growing number of Linux distros are available that are tailored to a specific purpose. Many are related to information security. This is in part due to the requirement for penetration and security testing devices to be isolated from the internet and parts of their host environment wherever possible, but also because of the large number of specialist tools that are required in this area. Kali Linux is a Debian-based distribution specifically designed for penetration testing and maintained by Offensive Security, a respected penetration-testing training provider with a long history in the industry. As a successor to the similarly well respected Backtrack toolkit which was originally based on Knoppix, the distro contains over 600 pre-installed packages and can be either installed locally or run directly as a live-boot distro, from…

The majority of Linux releases work on a fixed release cycle. A version is released, it will receive updates for a set period of time and after a release drops, work will begin on its successor. This works very well for ensuring stability (with beta and release candidates), but it adds an extra overhead for users as updates are applied and delays the speed with which the latest package updates can be delivered to users. A rolling-release distro instead delivers packages to users on a rolling basis, helping them stay up to date much more quickly, albeit potentially at the expense of ultimate stability. One of the most popular rolling-release Linux distros is the aforementioned Arch Linux; however, the rolling-release version of openSUSE – Tumbleweed – potentially brings the concept…

“Other client devices can connect to that local server without needing any internet connectivity” Sacatepéquez, Guatemala. You won’t find the village of El Rosario and its corrugated iron and breeze-block houses on any printed map. Ironically, you can find El Rosario on Google Maps but the village itself doesn’t have internet access. Such a luxury is a number of bus rides away and not a journey you’d want a child to take alone. Reducing the educational limitations for kids who grow up in places like El Rosario requires breaking vicious cycles that are generations-old: “The kids that don’t finish primary school end up working in the fields with their fathers,” says Sandra Castro, a teacher at the local school, Escuela Nacional El Rosario. “Our desire is to change that.” One…

One of the things that the Java language is particularly good for is designing graphical user interfaces, or GUIs. In this second part of our Java tutorial series, we’ll be learning how to use the powerful graphics library JavaFX. In last month’s tutorial, we created a text-based game in which a player can walk around a map, collecting eggs which hatch into different animals. In this tutorial, we’ll be replacing the console-based input and output components of this program with a GUI created using JavaFX, which will help to demonstrate the power of inheritance and polymorphism in Java. A word of caution – JavaFX is a huge, feature-rich library and we can’t cover everything you’ll need in one article. The aim of this month’s tutorial is to teach you enough…

“I’ve been into electronics for a very long time” Components list • Raspberry Pi Model 3B • Raspberry Pi 7-inch 800x480 multi-touch capacitive touchscreen • Lexar 32GB microSD card • Adafruit PowerBoost 1000C charger and 3.7-to-5V converter • DS3231 temperature-compensated real-time clock • USB audio adaptor • PAM8302-based mono class D amplifier • 25mm 8Ω speaker • Battery monitor and shutdown control circuit • 6200mAh Lithium-polymer battery, giving 4 to 12 hours battery life (6 hours watching YouTube) • SPDT slide switch and 3× small push-button switches • USB and micro-USB ports • Raspbian Jessie Mouse buttons Three function keys were added. These were made using switches from a broken mouse mounted on a stripboard. The buttons themselves were made from the legs of old ’70s-style transistors that were epoxied…

Any evil genius worth their salt knows that a key part of their arsenal, besides a secret base inside a volcano, is a doomsday device which when triggered will release nuclear launch codes. Not all of us have aspirations of world domination, but we can appreciate the usefulness of a doomsday device which can execute commands at a moment’s notice. In this project, we’ll be using the versatile Pibrella add-on board (available for just £10 from http://bit.ly/Pibrella) to build your very own device. Aside from having the requisite big red button, the board also comes with a handy buzzer which can be programmed to signal a countdown when you activate the doomsday switch. The Pibrella also has three built-in LEDs (green, yellow and red), which we’ll also use. Once the…

While we don’t normally cover projects that are ‘about to be open source’, and Fiwix is holding off licensing until the upcoming 1.0 release, we thought you might like to take a look at this. Once upon a time, everyone seemed to be writing their own operating system. Not just Linus Torvalds, but in the late ’90s there were small (or literally quite tiny in the case of floppy-based OSes like V2OS, which was written in assembly language, or the early QNX floppies) and medium-sized OS projects everywhere – many POSIX compatible, so fitting in with the GNU/Linux ecosystem. The Linux kernel itself began because Minix, the educational UNIX-like OS project on PC hardware, wouldn’t accept patches which radically altered its direction. Fiwix is an educational hobbyist project: a UNIX-like…

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Following in the footsteps of US reseller System76, Newcastle-upon-Tyne based company Nimbusoft is launching a range of desktop and laptop computers that will ship with Ubuntu Budgie pre-installed. Five laptops – ranging from the Ceres at £299 up to the heavy-duty Vulcan at £1,299 – are available, alongside a pair of all-in-one desktops at £599 and £699. All prices are for basic configurations and all models can be configured with the CPU, RAM, storage, drives, graphics card and operating system of your choice. Offering elegant cases and backlit keyboards, multi-touch trackpads and USB 3.0 ports, these devices are pitched as Linux-based rivals to Apple’s iconic hardware designs. Taiwanese OEM Clevo is providing the hardware. While Ubuntu 16.04.3 LTS is the default choice, Ubuntu Budgie 17.04 is available on all devices.…

Cross-platform users are being targeted with a new Facebook Messenger scam, which persuades the victim to download adware. This tailored attack addresses you by name and offers a link to malware based on your browser and operating system. While Windows users get a dedicated landing page and executable to fix Flash Player, Linux users are given a landing page that encourages them to add a PPA before installing some extra software. Of course, the attack is disguised. A Facebook Messenger box will pop up, addressing you by name, followed by the word ‘Video’, an emoji, and the link to the landing page. There’s no immediate reason to assume it’s anything but a spam message… but video clips are so enticing, aren’t they? For veteran Linux users, the dangers of unverified…

Linus Torvalds announced Linux 4.13 final, noting that some last-minute regression-squashing heroics in the memory management layer from Jérôme Glisse had helped to keep the release on time. In his announcement, Linus calls out “one very _small_ change” in particular, to the CIFS file system, which now requires a more secure minimal version (3) of the protocol by default. This means that the (hopefully) very small number of people still using SMB1 will need to take proactive action (adding a ‘vers=’ mount option, or fixing their network) to keep using that with Linux 4.13. Linux 4.13 includes many new and improved features, including next-interrupt prediction (which will save power for laptop users), support for improved swapping of huge pages, kernel structure layout randomisation via a GCC plug-in at compile time,…

Arch Linux is a lightweight and flexible Linux distro that targets more advanced users. Whereas an everyday distribution such as Ubuntu looks to install a broad set of applications from the off to support a range of different use cases, Arch takes a different approach – a minimal system base is installed, which the user can then tailor for their own purpose. Arch is very much aimed at users comfortable with shell usage – in most cases GUI configuration is not provided, configuration instead being managed by directly editing text files. While most distros have regular release cycles, Arch uses a ‘rolling release’ model as it looks to stay on the bleeding edge, negating the need for periodic ‘major release upgrades’. Arch’s repositories will typically always contain the latest stable…

Qubes OS is touted by its developers as ‘a reasonably secure operating system’ but in reality, it offers huge benefits over standard distros from a security perspective – if you are willing to put in a little bit of effort. Advocated as ‘the best OS available today’ by none other than whistle-blower Edward Snowden, this level of praise is the norm rather than the exception among privacy experts. Key to the Qubes OS concept is the concept of compartmentalisation. The distro focuses on splitting all of the activities you carry out in your typical use of your Linux machine into securely isolated compartments known as ‘Qubes’. The easiest way to think about each Qube is like a standard virtual machine, which makes sense – the underlying technology is the bare-metal…

Recommending the best lightweight Linux distro is always a tricky task. First, because Linux itself runs so well on low-end hardware that there are lots of candidates and second, because the low-end desktop environments can also run on a variety of distros. With that said, we’ve picked LXLE as our distro of choice. An obvious option for the best lightweight distro is Lubuntu, the Ubuntu flavour that comes equipped with the LXDE desktop environment. LXDE (Lightweight X11 Desktop Environment) is based on GTK+ 2 (although a Qt port is in development as the future for the product) and is also the default desktop environment for Knoppix, Peppermint and other good low-end distros. LXLE is based on Lubuntu, but it is particularly tuned to be a drop-in and go OS, primarily…

 Now we are comfortable writing shell scripts, we can start to think of Bash scripting as a programming language in its own right. Indeed, many programming languages, such as Python and JavaScript, include REPLs (read-evaluate-print-loops) that allow you to interpret commands in real time. In the same way, the command line takes the role of a REPL for shell scripting: when you're writing a script, you can try out commands at the command line until you get them right, before copying them into your script. “Most languages provide a simple for-loop construct, and Bash scripting is no exception” Bash scripting is a surprisingly fully featured programming language, and in this tutorial we'll meet conditionals, for loops and functions which behave much as they do in other languages. We'll also see…

We reported on the long-running battle for the soul of Arduino last month [News, p8, LU&D182] and the fight for the Arduino trademark appears to have finally ended after BCMI, a company created by Arduino co-founders Massimo Banzi, David Cuartielles, David Mellis and Tom Igoe, acquired full ownership of Arduino AG. When Arduino LLC was founded in 2008, it registered a trademark in the US and later attempted to do the same in Europe. However, Gianluca Martino’s firm Smart Projects, which manufactured the boards, already held the trademark in Italy. Royalties were paid to Arduino LLC until 2014, when new Smart Projects CEO Frederico Musto renamed the company Arduino srl. The two Arduinos then entered a legal battle over the rights to the trademark which was settled last year, resulting…

We will create a Python script that connects directly to a Minecraft game running on another Raspberry Pi, which will enable us to have some fun with their game world. We’ll have the ability to manipulate the character, the environment, and place blocks, as we’ve done in the previous tutorials, but this time we’re working on someone else’s game. We’ll be able to have pranks galore, but it should be mentioned that this should not be done without prior permission of the third party. This tutorial is written under the assumption that you’re running Minecraft Pi Edition on a Raspberry Pi. No additional software is required. If you’d like to run this tutorial on your own flavour of desktop Linux, we’ve also put together a number of tools to ensure…

"How do you write code that uses threads well?" Several articles in this column have covered different techniques to accomplish specific tasks. What we haven’t covered, so far, is how best to deal with the case when your Raspberry Pi project needs to manage several different tasks concurrently. This month, we will look at how to use the multitasking capabilities within Python to manage multiple tasks. In the standard library, there are three main modules available. They are threading, multiprocessing and concurrent. Each has its own strengths and weaknesses. Since these are all part of the standard library, there should not be anything extra that you will need to install. First, we will look at the threading module. There are two ways that you can use this module. The first…

Where to start with a 200MB package which offers 30,000 Java classes for computation and visualisation? DMelt (as DataMelt is commonly abbreviated to) is a whole platform – working with Python/Jython, BeanShell, Groovy, Ruby, as well as with Java – for statistical calculations, advanced numeric computation, big data volumes, and modelling in areas ranging from financial markets to engineering. Its vector graphics image outputs come in all the usual formats, and can be incorporated into LaTeX docs. Starting up (via the included shell script) for the first time presents you with an ‘Introduction to DataMelt IDE’, and a three-pane view into DMelt that most users will feel at home with – at least enough to start clicking around and trying out some included examples or calculations and visualisations on their…