Linux User & Developer -julkaisun No. 177 -irtonumeron sisällysluettelo

This issue » Meet the man behind MeArm, p12 » Get the right VPN for you, p58 » Pi Zero W reviewed, p87 Change is sometimes challenging. When I began writing this column, as your new editor, our offices were in a state of flux. LU&D had landed in Bath and the whole building was being refurbished. Every day the new team could hear the steady thud of sledgehammers and watch the lazy decent of ancient dust from the ceiling above. Today, we’re sitting in bright, clean surroundings with breakout zones and snazzy sofas (no beanbags, fortunately). So, yes, change can be painful, but my hope is that you’ll come to appreciate this one, and I’m very keen to hear from you, dear readers. What do you like about LU&D…

Valve has massively improved the gaming capabilities for millions of Linux users around the world, and its show of support for all things open-source is set to continue with the launch of SteamVR for Linux. The crux of the announcement showcases all the information developers need to create Linux-based content for the HTC Vive headset, as well as a wide range of extra hardware and tracker accompaniments. At the time of writing, it’s yet unknown as to what other VR headsets will support Linux desktops going forward. The project is very much in the beta phase, meaning the current crop of options available for developers are limited. An NVIDIA-based driver, built on the OpenGL successor, Vulkan, is the recommended choice of card to use at this time. Valve has opened…

Top 10 This month While we see a couple of new names being added to the list this month, Mint is still leading the way when it comes to the total number of downloads. Highlights deepin deepin is making a welcomed return to the top ten this month, as it proves that Debian-based distributions can merge great usability and looks together. Its recent 15.4 beta update has proved to be a success so far. Manjaro Linux Despite announcing the closure of its ARM spinoff (see above), Manjaro continues to provide users with a user-friendly desktop experience that you can’t help but love. elementary OS Thanks to its sheer simplicity, elementary OS has proven to be a permanent fixture in the top ten every month. Expect an update to hit…

Resources NGINX www.nginx.com NGINX is a lightweight, high-performance web server that can run on almost all the major platforms and has increased in popularity due to its impressive performance and easy setup. According to Netcraft’s February 2017 report, 28.3 per cent of all high-traffic websites, such as WordPress, Hulu and GitHub, use the NGINX web server. Putting this into perspective, NGINX was at 16.3 per cent in January 2016. Unlike traditional servers, NGINX does not use threads to handle requests, but a much more scalable event-driven (asynchronous) architecture. However, increased popularity means increased security concerns. Since NGINX serves thousands of websites, a simple security vulnerability could lead to huge financial losses. In this tutorial, we will explain third-party modules, such as NAXSI and Fail2Ban, which you can use to make…

Resources Nmap https://nmap.org Ubuntu Server https://wiki.ubuntu.com/BasicSecurity When we set up a Linux system over a network, we face a number of security challenges and though we may be interested in keeping our Linux system off the network that may not be a feasible solution. In this tutorial, we’ll cover the various ways of securing the Ubuntu Server over a network. Most Linux systems that are used in large enterprises are configured as servers, which offer services to the remote clients over a network. The Ubuntu Server distribution (distro) has the potential to provide thousands of services, and many of them are listed in /etc/services file. In this file, the information is structured in three columns: The left column indicates the name of the service; the middle column has information about…

STREISAND Streisand is an easy-to-deploy VPN suite There are a number of options when deploying your own VPN server. You can take a bare Linux install and deploy your own individual packages (which, admittedly, does give you the highest level of control), but this is extremely time consuming. The alternative is to use a tool to deploy a VPN server for you. A number of open source tools are available with this feature, like Streisand. The Streisand script sets up a new server running L2TP/IPsec, OpenConnect, OpenSSH, OpenVPN, Shadowsocks, sslh, Stunnel, a Tor bridge and WireGuard (see p61). This provides you with a host of different connection methods you can use to suit your needs across a wide range of platforms. It is particularly clever in that it also generates…

What you’ll need • SenseHAT Humidity is a measure of how much moisture or water there is in the air. In this tutorial you will use Python to build a real-time humidity display. The program takes and stores a humidity reading using the SenseHAT’s on-board sensor. Then it calculates a simple ratio to determine how many LEDs to turn on. In essence, the higher the humidity the more LEDs are turned on. Then the number of LEDs that need to be turned ‘off’ is calculated and these are added to the list. Finally, you’ll set the program to display and ‘turn on’ the required number of LEDs. The program continually loops so both the reading and LED display is updated as the humidity changes. 01 Attach the SenseHAT Ensuring that…

In the previous article, we looked at how to install the port of Anaconda for the Raspberry Pi in order to have a bit more control over the Python environment. This is so we can take on more complex projects and still have a relatively clean environment. This means we need to create new projects and manage them. To create a new project, use the following command: This will create a new environment, named 'project1', with the core you need in order to run Python programs. If you already know that you will need certain modules, you can include them during the creation. For example, if you are doing a project on bioinformatics, you may want to have biopython available, as below: You can now switch to the new environment…

ClojureScript is Clojure – a modern Lisp that normally targets the JVM – compiled to JavaScript. Along with simple syntax and very expressive code, you get Clojure’s powerful macro system and the benefits of immutable data. This last part is a huge gain as increasingly complex software often features difficult-to-find bugs involving uncertainty over state. This isn’t the place to go into JavaScript’s shortcomings – but despite many plus points, it’s not the best language for robust, maintainable solutions to complex coding problems. Installation options include Leiningen, Maven and Boot, but the simplest is downloading the standalone ClojureScript JAR, which will run on any Java 8 (or above) installation. The excellent Quick Start guide on the ClojureScript website quickly steps you through a “Hello, World!” example and along the way…

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1 Pi Camera V2 This quintessential camera is the offical accessory from the Raspberry Pi Foundation. It’s a high-quality 8-megapixel snapper, which features a fixed-focus lens. While it’s capable of reproducing 3,280x2,464 images, there’s video support for 1080p at 30FPS, or 720p at 60FPS. 2 WDLabs Media Stick If you love creating entertainment projects, this is the accessory for you. The Media Stick is fully user-upgradable, with a built-in compute module programming mode. It also boasts a full HDMI port, dual USB ports and an additional micro-USB port. 3 Adafruit PiTFT This tiny 2.8-inch 16-bit display is made solely for use on the Raspberry Pi. As well as boasting a resistive touch overlay, it can use the display as a central console, media player or as a substitute for a…

“The MeArm Pi is a robot arm that a child can build. You can run it from a Pi” “The world of robotics is notoriously hard to get acquainted with, especially if you aren’t coming from a development-based background. It’s a problem that thousands of people face every year, but also something that Mime Industries has looked to quash. The company has introduced a range of open-source robotic kits, which strip back the complexity of building robots and lay the foundations for new users. At the helm of Mime is Ben Pirt, who has a varied history in working on both energy monitoring hardware and renewable technologies for the developing world. While his original work in the world of robotics was solely done in his spare time to help educate…

Upload your data Seafile makes it simple for you to manually upload your data into an existing file structure, as well as allowing you to create a new one. Share your data Any of your files and folders can be shared from Seafile and you can add password-protection, and even auto-expiration for sensitive data. Anything that has been shared can be instantly unshared, too. More than just file storage Other options are available with Seafile, such as a personal wiki. You can also manage which devices are linked to the account. While peer-to-peer syncing solution might seem attractive for collaboration involving large files, it isn’t 100 per cent reliable. Having that extra degree of safety could be the difference between success and failure, which is where Seafile comes in. Offering…

SuExec (short for Switch User Execution) is a system that enables Apache users to run CGI and SSI files under a different user ID to the one that runs the web server. Normally, these programs are executed as the same user as the web server, for example www-data on Ubuntu and some other distributions (distros). Use of SuExec can considerably reduce the security risks that occur from allowing users to develop and run their own CGI or SSI scripts, particularly in a multi-tenanted environment. This is because SuExec performs a number of security-related checks, such as ensuring that the directory containing the script is only writable by the owner user – the web server will return an error 500 if this is not the case. Keep in mind that the…

You’ve read about the different VPN options and why a VPN is a useful tool to have in your Linux armoury. In this guide we’ll take you through the process of signing up for and configuring a VPS with a couple of different providers, then installing Streisand or Algo to suit your needs before finally configuring your client to connect to your new VPN. So where do you deploy your VPS? All of the best providers offer some sort of free trial, so you can run a VPN without incurring any cost for at least a month, if not longer. ArubaCloud is our cheapest provider, offering Ubuntu VPS servers with 1 vCPU, 1GB RAM, 20GB storage and 1TB of bandwidth for a €1 per month with a €2 euro credit.…

What you’ll need • Suitable for all models of Pi (Pi Zero recommended). For security reasons, you need a dedicated Pi for this project. As you’re probably aware, the cryptocurrency Bitcoin can be used to make anonymous and irreversible online payments, similar to hard cash. Bitcoin is a huge leap forward for privacy-minded people, but the fact that it’s a digital currency means that hackers often target owners of Bitcoin software wallets. In this tutorial, we’ll explore a solution using the lightweight Bitcoin Wallet Electrum on the Raspberry Pi. The Pi will host a ‘cold’ wallet which is kept offline at all times. You’ll also set up an online ‘watching’ wallet on another computer so you can see payments as they come in. Payments are only sent by generating a…

RAM 256MB Storage 512MB Specs Based on Devuan GNU Live CD or USB compatibility While some people like to explore the outer regions of what’s available in the world of Linux distributions (distros), the vast majority will stick to the safety and confides of the usual suspects. Refracta falls very much into the first category as being somewhat obscure, but it delivers all the features and tools you need for an enjoyable user experience. The distro is based off the Devuan system-free fork of Debian, and sports a close resemblance to the minimalist Puppy Linux. While any distro would have a tough time wresting the lightweight crown from Puppy Linux, there’s a lot to love about what Refracta brings to the table. During initial installation, we found that running Refracta…

When you want to convert text between Markdown, TeX/LaTeX and HTML format (as well as Lyx, and OPML), what do you use? Fortunately, that’s always been easy, thanks to the excellent command-line tool, Pandoc – which is written in Haskell and extremely reliable. However, not everyone is content to use command-line tools. Fortunately, PanConvert has arrived for such users and supplies a GUI front end to Pandoc, written in Python, with Qt5 widgets. Other Pandoc formats, from ePub to MediaWiki, are also supported and an extra click away, but the default options keep the interface simple. Installation of the binary is also through a GUI of sorts, with setup wizard and a click-through agreement for the GNU GPL. You will need Pandoc already installed on your computer – which should…

We’ve often praised the numerous security fixes found in each Linux kernel update, but one has slipped through the net for a considerable amount of time. Tracked as CVE-2017-6074, the vulnerability stems all the way back to 2005, where the kernel gained its official support for the Datagram Congestion Control Protocol (DCCP). As far as vulnerabilities go, this was one of the more dangerous ones. It could be exploited locally using heap-spraying techniques to execute malicious code directly within the kernel. What’s even more worrying, is that these sorts of exploits can be then combined with several other flaws that add to the remote hacker’s arsenal weapons against your desktop. However, thanks to the discovery made by Andrey Konovalov, a Google researcher by trade, the exploit has now been patched…

“Linus Torvalds announced the second RC (release candidate) of what will be Linux kernel 4.11. In his announcement, Torvalds was pleased to see things had been calming down since the closure of the 4.11 merge window (the period of time where disruptive changes are allowed). This briefing was a far cry from his original 4.11-rc1 mail to the LKML (Linux Kernel Mailing List) from the previous week, which included a lengthy rant about the failure of particular subsystems and contributors to the kernel to follow the established practice of soak-testing new features in ‘linux-next’. Established practice is for such new features to remain in ‘-next’ for an entire development cycle before asking for them to be pulled into the following kernel release. In his analysis of the 4.11 merge process,…

Resources OpenWRT https://openwrt.org The Raspberry Pi’s GPIO layout might not be to everybody‘s taste, but we cannot argue that the 40-pin header provides ample opportunities to connect all kinds of hardware. While many of the gadgets that we mention should be well-known to frequent readers of the Practical Pi section, we will, nevertheless, face a few small obstacles when getting them to run using OpenWRT. This article assumes that you are at the stage where we left off in LU&D176, [Tutorials, p34] and requires a custom OpenWRT build; if you attempt to perform the following steps with the stock repositories available from the OpenWRT project, it will not work. In principle, accessing hardware resources on microprocessors is handled by writing specific values into registers. These are special memory locations (as…

Resources A recent installation of Erlang A text editor such as Emacs or vi This is the fifth tutorial in our Erlang programming language series, and we are going to cover network programming, which mostly includes the development of TCP/IP servers and clients. The single most important difference between regular command-line utilities and network applications is that applications that work over networks and connect two machines also depend on every networking device and software that lies between these two machines! The best advice that we can offer developers that program network applications, is to know the theory behind the task they want to perform and know that networks fail all the time. Put simply, you should be aware that HTTP is using TCP, SSH generates encrypted network traffic that cannot…

The classic use case of a VPN is public Wi-Fi hotspots. If you are out and about with your Linux laptop (or any other connected device), then you might want to take advantage of some free connectivity provided by your favourite coffee shop. The problem with this is that you don’t really know what is happening to your data between your device and the service you want to use. It could be intercepted by other actors on the network or by a compromised Wi-Fi system in the cafe. If you are looking to send any data you care about, be it your social network or your online banking, using a VPN will ensure that all traffic going over the public network is safely encrypted. A very common use of VPNs…

"We had the idea of having the tree tell us when it was ready" Craig Durkins is the plant manager and co-founder at Concrete Jungle, a project used to help harvest unwanted fruit and provide them to the homeless community. Like it? While the detector could be a game-changer in its field, the work that Concrete Jungle for their local community deserves to be recognised. You can check out what they do, and how to get involved from the comfort of your armchair over at: www.concrete-jungle.org Further reading It’s safe to say that Craig has worked on several iterations of the ripening detector – six in fact! He’s been kind enough to detail the project over on: https://hackaday.io/project/16809. Data logging Craig has modified the Pi to be a reliable data…

"You can manage huge data sets with dask" Why Python? It’s the official language of the Raspberry Pi. Read the docs at python.org/doc. “There is a limit to what you can do to increase the capabilities of a single machine and once you do reach its limits, your only option is to move to using multiple machines and spreading the computational work around. But, traditional parallel programming can be messy and difficult to do well. Because of this, there have been several frameworks developed to try and wrap the complexity. This month, we will look at Dask and how to use it on your own Raspberry Pi cluster. Dask is a pure Python library that provides two major components. The first is a scheduling system that handles the management of…

Most people who need a professional audio recording solution are aware of Ardour, and are probably already using it, or one of its derivatives. But for everyone else, this is something you should try if you need to stray beyond very simple audio editing. [See Reviews, p92, LU&D176 where we suggested EKO Sound Editor.] Ardour stands out for its power and features, but part of that is a by-product of lead developer, Paul Davis, having been able to work on it full time for several years, with numerous contributions from other users and developers. Davis is able to do this as many users, from professionals and hobbyists, contribute a monthly subscription to the project. It’s perhaps a precarious funding source, but it’s working: if you find Ardour indispensable, consider subscribing…

Kodi has been around a while, originally as XBMC, and is a fairly complete media centre. Despite this, the team behind it have been working on improvements, and the new release features a “10-foot user interface” – in other words, one designed for viewing at that distance (three metres), which is the typical television viewing distance in most homes. Kodi will run and install fine from your distro’s repository, but, as the new interface indicates, is typically installed in a dedicated box to make a standalone media centre. In particular, support for various remote controls is very good. There are a number of choices for getting Kodi on a Raspberry Pi, though we’ve found that Pi 2 or 3 is best. But who has time to sit on the sofa…