Linux User & Developer -julkaisun No. 192 -irtonumeron sisällysluettelo

Welcome to the UK and North America’s favourite Linux and open source magazine. You may have noticed quite a ‘cloudy’ theme to this issue. I jetted off to Copenhagen to attend KubeCon + NativeCloudCon with thousands of engineers and developers. Cloud native is an industry on a steep upward curve and the complexity of technology is both impressive and frankly mind-boggling. Turn to page 32 to find what’s so exciting about this growing industry. We devoted the main feature to getting into private, public and hybrid cloud as, well, our reader survey indicated that it’s a subject you want to know more about. Thanks to everyone who responded! You are helping us make the mag better. And if you weren’t sick of fluffy clouds already, we show you how to…

Top 10 This month • In development (7) • Stable releases (25) Unsurprisingly, it is the month of Ubuntu 18.04 LTS, with various flavours of the popular distro being released within hours of the main version. Highlights Ubuntu Studio 18.04 Curiously only a standard release, Ubuntu Studio features a collection of open source apps intended for audio, video, and graphical media creation. Ubuntu MATE 18.04 Transitioning to GTK+ 3.22, Ubuntu MATE 18.04 features improved touchpad gestures, accessibility support for visually impaired users, and HiDPI support. Ubuntu Budgie 18.04 This is the first LTS release for the refreshingly simple Ubuntu flavour. It features new Budgie applets, a new GTK+ theme called Pocillo, features and fixes. Latest distros available: filesilo.co.uk…

NGINX is a household name in open source. It was first released 13 years ago as a web server and it can also be used as a reverse proxy, load balancer and HTTP cache. We spoke to Owen Garrett, NGINX’s head of Products, at the Kubecon + CloudNativeCon. He’s been in software engineering for 15 years and he knows his way around the cloud networking business, so we asked him what was happening in the industry and what NGINX had in the pipeline. Owen Garrett: At NGINX, we’re playing in the networking space, the service mesh space, the routing space, and we have some new projects which are moving into the application space. So that’s the part that I track and follow most of all. We see our users come…

Linus Torvalds has announced Linux kernel Release Candidate (RC) 4.17-rc5, noting that things “continue to look fairly normal”. This means that we should be on track for a more conventional kernel release-cycle of seven RCs prior to the final “GA” of 4.17. At this stage in the process, most of the remaining changes are to fix minor driver problems and bugs, but there are no show stoppers. If things continue to go to plan, the merge window of feature development for 4.18 should be open in time for full coverage in next month’s issue. Linux 5.0? Not quite yet Linus had previously started an aside about kernel versioning numbering. It turns out that with the release of 4.17-rc1, the kernel’s git history had hit the “six million git objects mark”.…

“One of the advantages of using a cloud provider is that you only use (and therefore pay for) what you need” The days of having to deploy your own servers to run a service on the internet are long gone – the cloud is big business. For the largest player, Amazon’s AWS (‘Amazon Web Services’), cloud provision is seriously lucrative too – AWS delivered Amazon $5.11bn in revenue in the last quarter, with a 45 per cent growth rate, demonstrating that organisations are signing up at a phenomenal rate. The breakneck pace of adoption isn’t limited to Amazon either; Microsoft’s Azure has a 98 per cent growth rate as it seeks to catch up with the market leader. Although public cloud still feels relatively new in technology terms, it can…

Coders want to write code. Coders don’t want to spend time setting up servers. These two reasons explain why the serverless movement has exploded, particularly over the last year. The first thing to understand is that serverless, of course, isn’t actually serverless – code has to run on a server somewhere – but with serverless, architecture developers don’t need to worry about such things. Capacity is automatically managed by the cloud provider in a completely transparent way. The serverless revolution really started with the release of AWS Lambda, which coined the term ‘FaaS’ (Function as a Service). It’s since grown to encompass similar services from other provides, including Microsoft Azure Functions and Google Cloud Functions. While the key selling point of serverless is to more rapidly move from development to…

Cloud computing is the biggest IT growth story of recent years. It has revolutionised server provision in the way that it allows resources to be shared, but for many businesses there has been a reluctance to adopt the technology because of concerns about security and overall control. The private cloud approach looks to allay these concerns by continuing to use dedicated hardware. Instead of talking about data being stored ‘in the cloud’ at a third-party provider, along with lots of other companies’ systems, it paints a more comforting picture to be able to point at racks in a building and say ‘Here’s our data’. But how do cloud computing principles apply when the hardware is owned or leased directly? At first look, a private cloud does indeed look a lot…

Serverless is essentially two things: functions and events. The rationale is that events happen all the time and everything emits an event; for example, when you upload a file to an S3 bucket in the cloud. These events will often be things you want to react to because they are important to your business, but you don’t want to have something, like a microservice, that’s idling away in the background costing money. This is where serverless functions can replace certain aspects of microservices that typically receive an event from in the cloud. Kelsey Hightower, software advocate at Google, used his keynote to suggest that it might be a little too early to limit this event-driven architecture. He felt serverless events could be democratised by standardising event wrapping, using an open…

If you are working on a Git project with a team, you might find yourself being added to the project as a collaborator, meaning that you can use git push to send your changes directly to the project. In such a case, you don’t need to create your own fork of the project in order to contribute to it. It might still make sense to create a separate branch if you want to work on some changes and you want approval from the rest of the team before merging them in. In that case, you can still submit a pull request by selecting the appropriate branch in the page that appears.…

1 Install Android Tamer Dealing with Android security gets a little easier thanks to Android Tamer, a virtual/live platform for Android security professionals. Download the OVA file from http://bit.ly/AndroidTamer4-GD and choose File > Import Appliance in VirtualBox to install it. 2 Look around Once the system has booted, have a look at the bottom-left menu labelled ‘TAMER’; most of the tools used for Android Security are organised here in sections: Development, Dynamic and Static Analysis, Forensics and so on.See http://bit.ly/lud_andtamer. 3 APK static analysis Spawn a net terminal and run mobsf. The Mobile Security Framework will start automatically. Then navigate to http://localhost:3000, choose the APK you want to analyse and upload it using the ‘Upload & Analyse’ button. Wait until the static analysis finishes. 4 Set up an Android Emulator…

The special functions get() and set() that we meet in this example are just one example of conventions in Kotlin. Conventions are a bit like operator overloading in C++: they assign a particular syntactic construct to a particular named function. For example, if we write a function called plus() that takes in two arguments and returns a value, we can automatically write a + b instead of plus(a, b). Other conventions are more sophisticated. For example, in C++ we can overload the operators <, >= and so on, but we have to write them individually; even if they all call a helper function, we still have to write a lot of boilerplate. In Kotlin, on the other hand, imagine a class has a method called compareTo() that takes in two…

The use of drones in warfare has raised ethical questions because it allows lethal actions to be carried out with no risk to the pilot who is controlling it remotely. We can but imagine, therefore, the controversy over any suggestion of introducing autonomous lethal weapons to the battlefield. In addition to the question of removing risk from the attacker, questions have been raised as to whether software should ever be given the task of making life-or-death decisions. Pragmatically, it might sound plausible – irrespective of whether it would be desirable – to produce autonomous lethal robots but to program them with the rules of engagement, including the Geneva Convention, so as not to fall foul of international law. However, research conducted at the Technical University of Darmstadt in Germany has…

SSL keeps data private in transit, even over public wires, but the server can still read the data that passes through it – so Nextcloud now provides end-to-end encryption for clients. This is currently available for the mobile clients but still in development for the desktop client, so its usefulness is a little limited but still worth using. To make it available, you first need to enable the Default Encryption and End-to-End Encryption apps, then go into your mobile client and refresh the account. If you tap the menu next to a folder, you will now see an option to encrypt it. Tap the folder and it will display your encryption passphrase, which you should write down and put in a safe place – not the back of your phone…

Resources Maker Life Weather Station www.makerlife.co.uk Maker Life’s tagline is ‘coding for kids’; it produces pre-packaged development kits for parents, teachers and children with an aim of making coding fun and easy at low cost. We’re going to take a look at its most comprehensive kit, the Weather Station, and see just how much one can learn about the world around us from a Raspberry Pi Zero W and a bunch of sensors. This kit is a bit of a doer-upper. We’ll need to spend some time building the weather station and putting the sensors together before we can get down and dirty with any Python code. There are no soldering requirements, but the kit is moderately difficult to assemble. It seems important to Maker Life that its kits…

Specs CPU 1.8 GHz minimum Graphics 128 MB recommended RAM 1GB Storage 5GB Licence Various free software licences Available from  https://trisquel.info You can be forgiven if you haven’t heard of Trisquel; the distribution had its last stable release over four years ago. But, as the release announcement notes, the Free Software Foundation (FSF) has been using it to run the LibrePlanet conference since last year, and it powers all of its new server infrastructure as well. Trisquel was initiated by students of the University of Vigo in Spain who wanted to create an educational distribution that supported the Galician language. But the project soon outgrew this initial scope and became a fully free distribution with multilingual support. Trisquel was officially presented in April 2005 by Richard Stallman himself, and is now…

Just like music players, Linux has a long list of backup utilities as well. What sets Borg apart from the rest is its efficient execution of the backup process. Borg is a Python-based CLI app with a host of useful features, such as incremental backups and authenticated encryption using the 256-bit AES algorithm. You can further save space by compressing backups with LZ4, zlib or LZMA and can even lock them with a password. Another interesting feature offered by the app is the ability to manage backups remotely. You can easily mount Borg-created backups as FUSE volumes that can then be accessed using any modern file manager. Although other backup utilities can also take encrypted incremental backups over remote connections, Borg distinguishes itself in the way it implements such features,…

01 Optimise your website images When uploading your website to the internet, make sure all of your images are optimised for the web. Try using jpegmini.com software; or if using WordPress, install the EWWW Image Optimizer plugin. 02 Host your website in the UK Make sure your website is hosted in the UK, and not just for legal reasons. If your server is located overseas, you may be missing out on search engine rankings on google.co.uk – you can check where your site is based on www.check-host.net. 03 Do you make regular backups? How would it affect your business if you lost your website today? It’s vital to always make your own backups; even if your host offers you a backup solution, it’s important to take responsibility for your own…

“Ubuntu Touch was developed with the goal of being Android-free” Purism’s forthcoming Librem 5 phone will run Ubuntu Touch in addition to PureOS, it has been revealed. The device, which is set to be the most anticipated new mobile launch in years, will have three operating system options: Purism’s PureOS, PureOS with KDE Plasma Mobile, and now Ubuntu Touch. Since Canonical abandoned the mobile version of its Ubuntu desktop, Ubuntu Touch has been maintained and updated by UBports, a Canonical-free, community-based project. Unfortunately, device compatibility has been limited to a handful of handsets, such as the Nexus 5 (Hammerhead), OnePlus One, and the Meizu Pro 5. Ubuntu Touch – complete with its phone-to-desktop environment ‘Convergence’ – needs a modern, new platform, and Librem 5 looks set to be the answer.…

Released in April, Unit is the first of NGINX’s new projects. It’s a very lightweight application server that can run code in lots of different languages while being managed through an API. This means, says Garret, you can make configuration changes very, very quickly. The idea for Unit stems from the growth of microservices, where companies are re-architecting their applications and breaking them into small components that they can run in containers. The theory, adds Garret, is that microservices allow you to iterate more quickly and develop in parallel: ”It encourages developers to use the best tools available to them for each problem that they have to solve. They don’t have to use the same application stack everywhere. Maybe they’re building the web front-end for the application, and PHP is…

Within the public cloud space, there are several key players in competition with each other. As they all attempt to entice organisations to use their products, this is great news for the end user. One way in which this manifests itself is with ‘free tiers’ – a basic service level offering at no cost, or with free trial credit. It’s possible to spin up a complex public cloud environment with a whole host of providers including Amazon AWS, Microsoft Azure, Google Cloud Platform, Oracle Cloud, DigitalOcean and even Alibaba Cloud without spending anything and often without entering any payment details.…

Google Cloud Platform provides an easily accessible interface for those creating Cloud Functions for the first time. The console, available via your account, provides a destination URL for a HTTP trigger event, an inline editor for Node.js (ZIPs can also be uploaded), and settings for timeout and memory requirements. After specifying an entry point to the provided code, simply press Create and you’re ready to test by loading the provided HTTP endpoint. The process is a great demonstration of how powerful serverless is – minimum effort for a full (albeit basic) code deployment!…

All the large cloud platforms, whether public, private or hybrid specialised, offer tools to migrate your existing physical machines to the cloud. One of the leading solutions, and the one chosen by Google to power its migrations, is CloudEndure. This technology specialises in providing a resilience suite that encompasses not only cloud migration, but also continuous backup and disaster recovery. What makes the CloudEndure solution unique, and ideally suited to switching to a cloud infrastructure, is that it uses continuous block level replication to synchronise machines on an ongoing basis, supporting all the most popular operating systems and applications. There’s no requirement to switch infrastructure when the initial sync is complete, as the destination server stays up to date and you can make the move in your own time. The…

The Cloud Native Computing Foundation’s first KubeCon + CloudNativeCon of the year took place in the Bella Center, Copenhagen. It’s a giant greenhouse of a building with snaking industrial pipework and connecting concrete bridges; a vast container made of glass letting in light. It’s a suitable setting for an industry that’s evolved rapidly from the release of Docker’s superstar container technology back in 2013. Attendance has rocketed to 4,300 this time, according to Dan Kohn, executive director of the CNCF, which is almost triples that of a year ago in Berlin – but that’s not surprising, as the cloud native computing industry is meeting the business world’s demand for more scalable, agile applications and services that can be run across multiple geographical locations in distributed environments. What’s impressive about the…

What’s the goal with Ballerina? If you’ve ever worked on an integration project and you’ve done it at scale, there is an integration gap that exists – and it’s very frustrating to developers. You have two choices. You can either use something like an Enterprise Service Bus (ESB), which acts as a man in the middle – a router. That experience makes it possible to do integration at scale, but the developer experience is awful. You have to lay down these servers. You have to go and find and configure these connectors to these other end-point systems. The actual logic that goes in between is usually a combination of code and a bunch of XML using XPath. It all works, but it’s not a great developer experience. And it’s not…

Last time, we set out to build a coffee-pod-dispensing machine powered by an Arduino. In part one of this tutorial, we programmed the Arduino to extract information from an RFID card and had it pass the data to a Raspberry Pi so users could be identified. If a user had enough money on their account, the Pi would send a return message, telling the Arduino if it should give out a coffee pod. In this part, we will use this setup and build a prototype machine around it. We will begin by considering the design of the dispensing mechanism. This is a particularly important step as it can greatly alter the complexity of the project. We will then add additional hardware – a motor and an LCD. Finally, with all…

Resources Jupyter Notebooks http://jupyter.org IPython https://ipython.readthedocs.io/en/ stable Line by line profiler module https://github.com/rkern/line_profiler C-extensions for Python http://cython.org/ As a prominent language in the open source community, Python has a number of options available when it comes to code development. These range from earlier code editors like idle, to very feature-complete IDEs such as PyCharm. Many people actually fall somewhere in between these two extremes in terms of their coding needs. This is where Jupyter Notebooks have become a very popular option, falling between a simple editor and a full-fledged IDE. In many scientific disciplines, Jupyter has become the de facto interface. But how can you make the best use of Jupyter and get the most out of it for your own code development? This issue, we will…

There is a close correspondence between Java code and equivalent Kotlin code, where the Kotlin is often more concise. There are a number of tools available for converting Java code into Kotlin: for example, https://try.kotlinlang.org has a useful converter built in (see Figure 7). The IntelliJ IDE has built-in Java-to-Kotlin conversion, as does the Kotlin Eclipse plugin. In IntelliJ, you can even copy Java code and paste it into a Kotlin buffer, and it will automatically be converted.…

Most programming languages have a function for generating random numbers. These are, of course, only pseudo-random, following a long and convoluted pattern which eventually will start to repeat. For most applications this isn’t a problem, but it’s not hard to think of cases – online gambling, perhaps – where even the remotest possibility of someone being able to predict the next number in the sequence would pose a risk. It’s a shame, therefore, that genuinely random numbers are uncomputable. For example, Premium Bond winners are picked by computer, but the random numbers on which the software relies are generated by special hardware. Called ERNIE – or Electronic Random Number Indicator Equipment to its friends – it uses the thermal noise in transistors as its source of truly random numbers. This…

Nextcloud has just released a new version, Nextcloud 13, which makes this the perfect time to have a look at it. First, though, if you’re asking the perfectly reasonable question “What is Nextcloud?”, a quick explanation. Nextcloud is a self-hosted cloud server. There are plenty of commercial services out there for cloud hosting, and some very good ones at that, but use any of them and you are trusting your data to another company, possibly one that makes its money from parsing data. With a Nextcloud server, you are in control; you decide exactly what is stored where and who has access to it. The downside of this is that it is also up to you to keep the service running reliably, something the commercial providers have many years experience…

Like it? Aaron is a software developer for eBay and Davis is a mechanical engineer at an aerospace company. Further reading They run a Youtube channel (www.youtube.com/c/HackerShack) and a website called Hacker Shack (www.thehackershack.com) where they share interesting DIY builds. With some acrylic sheets mounted on a wooden frame, the hacker duo at Hacker House have managed to transform a regular LCD monitor into a 3D ‘holographic’ music visualiser that’s a sure head-turner at any party. The device projects an image from a monitor down onto an acrylic pyramid, or frustum, which then creates the holographic parallax effect. To add to the futuristic aura of the device, Aaron and Davis have connected a Flick board from Pi Supply, which enables them to use Jedi-like hand gestures to control playback, volume…

This is a great project for collaborative working between an engineer interested in physical computing and a coder who wants to put their Python programming skills to the test. This kit is very much in-line with the Raspberry Pi Foundation’s philosophy of supporting a new generation of ‘Digital Makers’. Here’s our team, left to right: Nadia, Olivia, Calvin, Weronika, Elisabetta, Anastasia and Ashante, from year 10 GCSE classes Lovelace and Babbage. If you’ve ever wanted to tinker around with the GPIO pins on your Raspberry Pi, create your own circuit and write programming code for it, this is the project for you. It wouldn’t be very difficult to take this kit to the next level by introducing your own sensors for monitoring ambient light, noise and even pollution levels. It’d…

The Linux desktop has no dearth of audio players, but the popular ones all predate the modern desktop environments they run on, which results in usability issues for many users. The KDE developers are looking to address this problem by creating a new music player from scratch. It’s called Elisa and it has just had its first official release. According to the developers, the app “strives to be simple and nice to use.” While it’s understandably well-integrated with the KDE Plasma desktop, the developers want it to be just as comfortable on other desktop environments like GNOME Shell, as well as on other platforms such as Windows and even Android eventually. While Elisa currently lacks all the bells and whistles you’ll find in other modern music players, it is fully…

QuiteRSS is a simple cross-platform feed reader that works well even on older, low-spec machines. The app has all the features you’d expect from a news reader. It can pull in RSS and Atom feeds and helps you mark them as read, unread and favourited, and apply labels to each item as well. You can add a feed using the feed import wizard, which can also use a username and password if you are required to authenticate before fetching the news. QuiteRSS has a Webkit-powered embedded browser and can open news items in a new tab or in the external browser. The app offers plenty of customisation options. You can change the layout of the reader, change the default fonts and colours of the various items, and customise the notifications…

JanEnDi logged off and grinned. He’d arrived nice and early at the decrepit pay-as-you-go computer café. Despite its incredibly slow connection, he’d managed to find a job for the day, before they’d all been taken. Lucrative work too, with little investment up front for materials and plenty of opportunity to scam some extras. With a nod to the proprietor, he slung his green bag over his shoulder and took the three strides to the door. He shoved his feet into the pair of motorised roller blades that were released from their docking point as he paid the micro-credit. His signature code was now combined with the unique code of those blades and he’d be charged for the time he used them. While the blades glided towards his destination, he imagined…

After decades of it dismissing Linux, the past few years have seen the Redmond-based software giant become a fan of open source computing. While a Linux kernel at the heart of Windows itself remains unlikely, Microsoft’s support for things such as the Linux Subsystem for Windows 10, joining the Linux Foundation, and releasing the Windows 10 IoT Core for the Raspberry Pi proves that it at least recognises the importance of Linux to modern computing. Announcing the news on 16 April (which some took to be a late April Fool!), Microsoft President Brad Smith revealed “After 43 years, this is the first day that we are announcing, and will be distributing, a custom Linux kernel.” Designed to safeguard microprocessors in the Internet of Things and other compact devices, Azure Sphere…

NGINX, the open source project that you likely know and appreciate, is supported financially by a commercial business that sells support and some additional features more relevant to enterprise business, under the umbrella of NGINX Plus. This is a software load-balancer, web server and content cache that supplies production-ready features on top of what’s available in the community edition. This includes session persistence, the ability to configure NGINX via API and active health checks. “We have a more a managed cadence for releases,” says Garrett. “We provide support. We provide priority security fixes.” What was surprising at Kubecon was how few engineers and developers realised that NGINX Plus existed. If you’re someone using NGINX open-source in production, the company can provide you with a tuned, expertly maintained version. Not only…

• Public cloud Public cloud represents the largest focus for cloud computing – learn everything you need to get started for yourself. • Serverless A key growth area for cloud is serverless – removing the need to run your own ‘boxes’ at all. How does it work? • Private cloud For some applications, maintaining a private cloud is still the best option. Technology developed for public cloud helps simplify this. • Hybrid cloud Hybrid clouds are used for a number of reasons and can deliver the best of both worlds. Learn whether the hybrid mix is right for you.…

1 Create a DigitalOcean account To create your DigitalOcean account, head to www.digitalocean.com, enter your email address and choose a password. After confirming and validating your account you’ll arrive at the main dashboard. Use the code ‘DROPLET10’ to apply a free $10 credit. 2 Create your first droplet A ‘droplet’ is the Digital Ocean term for a server. After clicking Create Droplet you will be presented with a list of available Linux images for basic distributions, container distros or ‘one-click apps’ such as Ghost or Wordpress. Select the option of your choice. 3 Specify a droplet size Different sizes of droplets are available, with ‘standard droplets’ gradually scaling up in terms of CPU, RAM and storage (starting at $5/month) and ‘optimized droplets’ offering compute-optimised configurations for processor-intensive applications. 4 Choose…

1 Install serverless globally To install the serverless framework on your machine, you’ll need npm (part of Node.js) installed. Ensure you have Node installed using node -v and that you have npm installed with the command npm -v. Install globally with the command npm install serverless -g. 2 Log in to your account After the framework is installed, you’ll need to authenticate against the serverless online platform to allow your applications to be deployed. Use the command serverless login, which prompts you to sign in using GitHub credentials in your web browser. 3 Create the serverless function The next step of the process is to create the serverless function itself. Using the command serverless create --template hello-world creates a basic function. A number of templates are included for a variety…

As the leading cloud platform, OpenStack is a great way to get started with cloud technology and it’s very easy to install for yourself, either locally on your machine for test purposes or across a rack of physical servers using MaaS (Metal as a Service). Both options take advantage of a utility called ‘conjure-up’, so installing a practice system of your own exactly mirrors the process involved in a larger deployment. Full details on how to install are online at http://bit.ly/lud_try_openstack. After installing conjure-up from a snap package, the ‘OpenStack with NovaLXD’ spell walks you through everything you need to get started. The OpenStack Dashboard is installed as part of the installation ‘Horizon’; it’s a web-based utility to manage OpenStack services. From the dashboard you’ll can upload and manage images,…

We asked Brandon Philips, CTO of Red Hat CoreOS, to explain why this shift has occurred so quickly. Prior to Kubernetes and containerisation, Philips says “You got a whiteboard and drew out your thing: here’s the web server and here’s the database. After that you’d write a bunch of Bash scripts, source some Linux packages and wire stuff together and the thing that you’ve drawn on the whiteboard no longer exists; it’s translated into a bunch of scripts and recipes that you’ve followed and that gets modified over time.” However, it’s now possible to translate that diagram directly into an API: “You say this is going to be a deployment, this is a service and I’m going to tie them together with this metadata and you tell Kubernetes this is…

The main purpose of Git is collaboration on large software projects, particularly open source ones. One possible pitfall with this is that different collaborators might be working on the same code at the same time, and they might take it in two different directions. Last issue, we saw how we can use merging to reconcile changes from different collaborators. However, part of the Git model is that we should be able to look at the whole history and possibly revert some changes. In order to do this, it makes sense to keep track of contributions from different people individually, so that we get a full picture of the changes that have been made. This is where branches come in. A branch is a particular strand of work that may fork…

Metasploit ships with a bunch of multi-platform payloads out of the box; just pick the one you need and you’re good to go. But sometimes you need more. Imagine that you’ve found a vulnerable program for which there’s a Metasploit exploit module; you configure your classic Bind TCP shell payload and run the exploit against your target. So far, so good – except that you’ve left that target exposed to others as well. Wouldn’t it be great to add some customisation to this payload in order to accept connections only from a given IP address? Some years ago, a security researcher wrote a Metasploit payload for Windows called Hidden Bind Shell (see Resources). His was an interesting idea: to hide the listening port of the shellcode from unknown IP addresses.…

Resources Kotlin compiler Installation instructions in the article A Java IDE, such as Eclipse or IntelliJ (optional) If there’s one thing that can be said about the Kotlin language, it’s that programmers love to use it; in fact, it came second only to Rust as the most loved language in the recent Stack Overflow Developer Survey. Unveiled in St Petersburg in 2011, Kotlin was intended from the start to get around several of the problems present in Java, which is still the dominant language for enterprise programming. Indeed, Kotlin provides a number of constructs that are far more concise and elegant than their Java counterparts. Unlike some other langauges, however, Kotlin does not seek to replace Java immediately. Instead, there’s a strong focus in the community on interoperability with existing…

One very useful feature in Kotlin is the concept of null safety. In many languages, including Java, variables can take on a special value null that indicates that they have not yet been initialised. Code with null is prone to errors, particularly because trying to call a method on a null object raises an exception. Several languages have evolved clever ways of getting around this problem; Kotlin adopts an approach that keeps the spirit of Java, while making code more safe. By default, objects in Kotlin cannot be set to null; if we want this to possible, we have to declare them with a special nullable type, which is formed by adding a question mark to the original type. So val x: Int = null is not permissible in Kotlin,…

We’ve already described the proof that the Halting Problem is uncomputable as being a close parallel to the proof that the Bocca della Verità isn’t able to tell truth from a lie. If you want to know more, though, here’s the gist of Alan Turing’s own proof. We start by assuming that there exists a program that solves the Halting Problem. It’s called Halt_or_Loop, it takes as its inputs a program and its input data, and it computes a single output, stating whether the combination of the program and its data loops forever or halts. We can now envisage another program, illustrated here, which builds on Halt_or_ Loop by adding a few more instructions. Now, let’s think about using this new program as the input data to itself. If it…

1 Create a database user Create a separate MySQL user to access your Nextcloud database. You can do this with the MySQL command line client or phpMyAdmin. As you haven’t created the Nextcloud database yet, give the user full permission to start with. 2 Add any missing PHP modules Nextcloud requires several PHP modules. If you see a message like this, use your package manager to install the missing modules, then go back to your browser and refresh this page to move onto the next one. 3 Set up users Here you create an admin user within Nextcloud – you can add other admins later – and supply the credentials for the MySQL database. Moving the data folder to somewhere outside the DocumentRoot is a good idea. 4 Add some…

Resources PIC 16F1503 PIC programmer of choice Breadboard, wiring Combinatorial process computers became fashionable when the Arduino Yun hit the road; it combined a high-performance ARM SoC with an 8-bit controller intended for handling real-time and low-power tasks. A similar approach can be taken with the Raspberry Pi, combining the power-expensive process computer with a simpler secondary MCU. The Microchip PIC16F1503 is an extremely convenient candidate: it’s backed by an industry-leading IDE (MPLAB X with MCC), it’s cheap, can be had in a DIP case and can be programmed with a dirt-cheap programmer. The following steps outline the reduction of total power consumption. Due to space constraints, we aren’t able to discuss the (simple) power regulation circuits. On the PIC… Start MPLAB, and create a new PIC project based on…

With Universal Media Server (UMS) you can stream all kinds of media from your Linux computer via the Universal Plug and Play (UPnP) protocols to any DLNA-compliant device. DLNA is a certified implementation of the UPnP protocol that’s found on popular gaming consoles including PlayStation and Xbox, and even several TVs from popular brands such as LG, Philips, Sony, Samsung and more. UMS uses FFMpeg, Mencoder and Mediainfo to support virtually every media format. It’s written in Java, so you need to fetch OpenJDK from your distribution’s repositories. Then download and extract the tarball from UMS’s website and launch the server. You’ll be taken through a small setup wizard on the first run. UMS is fairly straightforward to configure thanks to its multi-tabbed graphical interface. UMS detects and lists all…

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