Linux FormatSeptember 2016的目錄

Jonni Bidwell The nouveau driver was a phenomenal reverse engineering achievement. It may not compete with Nvidia’s proprietary driver for gaming, but for a home theatre PC it’s fine and doesn’t require me to keep adding options to prevent tearing during video playback. Neil Bothwick It was probably releasing the kernel under the GPL, which allowed everyone to contribute to it and paved the way for a complete open source operating system built around it. Without that it would have been yet another interesting academic project that went nowhere. It also gave the GNU project something useful to do! Les Pounder Over the 25 years, the way in which Linux has been accepted by the public has changed dramatically. Now we see Linux in movies, supported for blockbuster games and…

“Let’s say you are a developer, an engineer or an administrator. Let’s say you have excellent skills and expertise. And let’s say you are looking for a job. You know exactly what you can do, of course. But do your prospective employers? Chances are they don’t. In the Open Source Jobs Report, a recent study by The Linux Foundation and Dice, 87% of hiring managers said they struggled to find qualified professionals for their open positions. Why is that? One part of the answer is easy: open source is different. The community operates in a much looser framework than its standard or proprietary software equivalent. In a world where collaboration is the highest principle, careers don’t necessarily follow predefined pathways. Benchmarks differ, and the criteria that usually lead recruiters are…

Thanks LXF, I was excited to see and read your tutorial on creating randomised music using Sonic Pi, I think it’s a brilliant area of computer science and fascinating to see how programming can be used within this different context. What I find interesting is also the randomisation aspect you demonstrate in your tutorial that I think is such a strength of computationally composed music. I’ve been experimenting with this kind of thing over the last year for my university dissertation project. I’m working with Dr Sam Aaron (the creator of Sonic Pi) and have developed a plugin for Sonic Pi that allows you to randomly generate musical canons with a single line of code. It uses a Ruby implementation of MiniKanren (a domain specific logic programming language) for generating…

Of course, there are plenty more financial applications available on your Linux distro than the five contenders that we’ve just reviewed and compared. The list extends to numerous other titles, some of which are open source while others are strictly proprietary. TurboCASH, TAS Basics, NCH Express Invoice, xTuple PostBooks, Invoice xPert, Moneydance, Appgen MyBooks, Nolapro and many others run on Linux just fine, but they are very niche solutions and some of them are quite pricey to purchase or use on annual subscriptions. It would be impossible to run a fully-fledged comparison of so many accounting titles, which is why we’ve tended to stick to the most recognised applications. As you can see, maintaining a ledger isn’t rocket science and even though you’ll definitely need some specialist knowledge to get…

Efficiently managing memory is one of the core tasks of the Linux kernel. The available physical memory is mapped into the address space of the kernel. If there’s more physical RAM than can be mapped into the kernel address space, the kernel must resort to highmem to manage the extra memory, eg 32-bit machines can only manage up to 896MB of RAM and anything above this (up to a maximum of 2^32 = 4GB) can only be addressed by means of highmem. However, these days, the reverse is true and the highmem mode is not required on 64-bit machines because the available address space is quite large. It’s the task of the kernel to manage the available memory and to correctly map the physical and virtual memory. For efficiency reasons,…

Linux is a monolithic kernel, which is to say that it is one large program as opposed to a microkernel that breaks up the functional components into separate chunks of code. However, one of the main characteristic of the Linux kernel is that it allows for dynamically loading and unloading components or modules as and when they are needed. Dynamically loading modules makes the kernel very flexible and also helps keeps its size to a minimum. You can either load and unload kernel modules explicitly or leave it to the kernel. Once a Linux module has been loaded it becomes a part of the kernel and has the same rights and responsibilities as any other kernel code. Linux also allows module stacking, wherein one module can use the services of…

At this juncture of the narrative we’ll take a quick detour to mention some other ‘pioneer’ Linuxes, now consigned to the history books. Like MCC, TAMU was developed at the Texas A&M University for in-house use only. Unlike MCC it included X-Windows, although numerous reports of ‘magic smoke escaping from monitors’ were attributed to its haphazard configuration utility. Yggdrasil (a bigol’ treein Norse mythology) Linux has the honour of being the first near-live Linux distro. It was distributed on CD-ROM but obviously required a floppy disk from which to boot. It’s noteworthy that Yggdrasil was released as a commercial product, but its $99 price tag was orders of magnitude less than that of the Unix systems available. TAMU and Yggdrasil have, like many others, largely been forgotten by history. In…

As previously mentioned, many distros apply various patches to their kernels. It may be that you need or want to do the same. These patches may be to support additional hardware or to enable extra features. They may not be in the main kernel source because they are too new, have not been sufficiently tested or are otherwise unsuitable. To show how it’s done we will apply a patch that gives a greater choice of CPU optimisations. Download the ZIP file from https://github.com/graysky2/kernel_gcc_patch and unpack it. The latest release of the patch requires at least version 4.9 of the GCC compiler being installed. You can check which you have by running gcc -- version . If yours is older, either upgrade or use one of the older versions of the…

This segment has covered a few stories which touch on the current resurgence in artificial intelligence and machine learning. While we wait to see whether this will lead to a glorious future where servers look after themselves and our cars can drive us to work while we sleep or the enslavement of the human race, we should sit back, put our feet up and enjoy a beer brewed by a benign artificial intelligence. London based IntelligentX (http://intelligent.ai) has combined brewing with machine learning to create four different types of beers which will evolve over time thanks to customer feedback and interpretation of the data by the company’s Automatic Brewing Intelligence (or ABI, for short). Drinkers use Facebook Messenger to answer questions about the beer and IntelligentX say reinforcement learning and…

Eagle-eyed readers will recall that LXF has covered OCaml in the past [see Code Academy, p88, LXF182], Juliet Kemp gave us a great intro to this high performance functional language. OCaml is descended from ML and as well as being functional in nature, also supports object oriented and imperative programming. It has a reputation for being very performant; indeed, the first I ever heard of it was on a website (www.tbray.org) where a typical file processing batch job was benchmarked using a variety of languages. OCaml for a while topped the charts on that particular task. Jane Street (a proprietary trading firm, https://www.janestreet.com/technology) has long championed its use and has funded some of the development work which has gone into improving things like the OCaml package manager, OPAM. Its blog(https://blogs.janestreet.com)…

The Pi Wars ran in 2015 and was a huge success, the event had various Raspberry Pi-powered combatants from teams of schools and enthusiasts from around the country. Battles were fought, tears were shed, harrumphs were said, prizes were awarded and good times were had. Held in Cambridge in the UK by the same team that runs the Cambridge Raspberry Jams, the obvious question is when is the Pi Wars 2016 event? The answer to that is that, it’s in 2017! It turns out that after listening to feedback from the last competition it was decided that a date in April would suit contestants better than the original date in December. The new date gives a much longer period in the usual school year (that starts in September) for teams…

In this Raspberry Pi tutorial we’ve just scratched the surface of what Turtle can do. Turtle is an easy-to-use tool with a whole host of options and here are some of them: Coloured shapes Shapes can have a colour fill applied to them after they are drawn. You merely have to say which colour to use, when to start the fill, and when it ends. Pen colours You can change the colour of your pen by using the pencolor() function and passing it a colour. Colours can be passed as arguments to the function and they can be the name of the colour or the mix of red, green and blue, ranging from 0 to 1 per colour. Here we see the colour red represented in both formats: Lifting the…

For the purposes of this guide, a Gmail account will be used to send an email when the switch is tripped, but the sendemail program can be used with any SMTP server provided you have the details. If you’re happy to use Gmail, head over to gmail.com and create an account. Next head to https://www.google.com/settings/security/lesssecureapps to switch on access for ‘less secure’ apps. Next, on the Pi, you’ll need to install the sendemail program and its dependencies and once this is all installed, type nano email. sh to create an empty file and paste in the following script, modifying it as needed: Use Ctrl+x to exit, saving your changes. Next, run chmod a+x email.sh to make the FTP script executable. Make sure to remove the # at the beginning of…

Xrandr is a powerful tool, but as with all good command-line tools, things can go wrong. If your displays get messed up, then simply logging off and back on again should reset them to their defaults, or you can try xrandr -s 0 to reset the main display to its default setting. If you’re unsure about whether or not a resolution will work correctly, try the following line when setting a new resolution: This will attempt to set your new resolution, then after 10 seconds revert to the original resolution. If the display goes blank for this time, the new resolution isn’t supported. Sometimes you may get a BadMatch error when attempting to add a resolution. This could be down to a number of issues. Try doing a web search…

The GPS module is a sensor and works by picking up a series of satellites that map the drone’s location. As the drone we’ve built is quite small it won’t be as accurate as larger craft, but it will still have a positive effect on the quality of flight possible. Mounting the GPS module can be an issue as it can be difficult to find a place on the drone that doesn’t get in the way of the propellers. Also take into consideration that every few flights your drone will need recalibrating, and this will involve you placing the drone on its back so the GPS pole will need to be removed. Once connected to the drone the GPS needs to be mounted. Unlike all other components that need to…

Our expert Mihalis Tsoukalos (@mactsouk) has an M.Sc. in IT from UCL and a B.Sc. in Mathematics. He’s a DB-admining, software-coding, Unix-using, mathematical machine. You can reach him at www.mtsoukalos.eu. LTTng Learn how to track behaviour and analyse data from your system LTTng is an open source tracing framework that runs on Linux. This enables you to understand the interactions between multiple components of a system, such as the kernel, C or C++, Java and Python applications. On the Ubuntu 16.04 distribution (distro) you can install LTTng as follows: After a successful install you will see at least one process related to LTTngrunning (see above, right for how the installation process looks in more detail): You can find the version of LTTng you are using with: Using LTTng LTTng does…

What has any of us achieved over the last 25 years? I can tell you the Linux kernel has developed into a Goliath with 17 million lines of code, that started life as one coder’s hobby and has turned into a world-leading kernel, which powers the majority of servers in the world (and apparently over 2.3% of desktops, (see p7)). That faintly smiling penguin we know and love as Tux propelled, what should be an unknown and uncared-for OS component to worldwide fame. No one wanders around talking about the Windows kernel, the Mac OS X kernel (sorry BSD!) or complains that their TLA doesn’t proceed that kernel’s name, but apparently Linux is known well enough that it can have entire magazines named after it! We’re here this issue to…

We’ve recently seen a number of positive moves by Nvidia and AMD, the two biggest companies in computing graphics, in embracing open source when it comes to open source drivers. AMD continues to be in our good books as it has just announced it’s giving developers access to the source code of its powerful physics-based rendering engine, Radeon ProRender. Plug-ins for the engine are available for popular 3D content creation tools, such as Autodesk 3ds Max, Solidworks and Autodesk Maya. ProRender is built on OpenCL and it can run on any hardware that supports the open standard, and by using the compute capabilities of multiple GPUs and CPUs, it can create state-of-the-art 3D graphics, with the engine available on http://gpuopen.com. Raja Koduri, senior vice president and chief architect, Radeon Technologies…

APRICITY OS 07.2016 The first stable release of Apricity OS, an Arch Linux-based distro that comes with both Gnome and Cinnamon desktops, is now available to download. This latest release includes a new system configuration tool, Apricity Freezedry, which allows users to easily configure the system. Gnome and Cinnamon themes and settings can be tweaked along with installed settings and enabled Systemd services etc. Also new is support for LUKS encryption, a more stable installer and improved touchpad support. To download the distro head to http://bit.ly/ApricitySs07_2016. BLACKPANTHEROS 16.1 A major new release of blackPantherOS – a distro that’s aimed at school, home and work use that was originally forked from Mandriva Linux, has been released – and for the first time the distro comes with the KDE Plasma 5 desktop.…

Welcome to the Makersphere A new event for the next generation of makers. June 2016 saw Makersphere, a new event, emerge from the Raspberry Pi community aimed squarely at parents looking to help their children get the most from their Pi gear. This was the first event run by the local tech community and teaching staff at Mary Magdalen’s Primary School in Penwortham and it attracted 370 people for the family fun day. The goal of the event was to offer classes and workshops based around popular technologies, such as the Pi, Codebug and micro:bit, to parents who weren’t tech savvy. The event also had other hands-on sessions for areas such as wearable technologies and 3D printing. There were sessions running all day covering introductions to the Raspberry Pi for…

Skrooge is more advanced than KMyMoney thanks to its Undo/ Redo feature, detailed transaction properties, powerful search engine, budget builder with auto-transfers and very good-looking reports that you’d expect from premier (and paid-for) online banking services. However, both Skrooge and KMyMoney lack tax accounting, vendor management and billing features that prevent them from being fully loaded financial tools. All of the above features are neatly integrated into GnuCash and although KMyMoney has online banking support (via OFX and HBCI protocols), GnuCash is far more advanced in terms of intercommunications with banks. In fact GnuCash is pretty comprehensive: it supports stock, bond and mutual fund accounts; it produces high-quality invoices (payouts, taxes and more), credit notes, stores and tracks them (auto numbering is used). In case you need to organise your…

“Today it powers everything from the Raspberry Pi to the New York Stock Exchange.” You wouldn’t realise it, but you’ve got software worth billions of pounds powering your computer. That’s what it would cost to redevelop the Linux kernel, according to estimates by the Linux Foundation. The foundation has dubbed the Linux kernel the world’s largest collaborative development project as it would take thousands of man years to rebuild from scratch. The latest release of the kernel contains over 19 million lines of code written in about a dozen programming languages, and most of the work is paid for by hundreds of multinational corporations that have thousands of dedicated kernel developers pitching into its development. Yet all of this work can be traced back to one solitary bespectacled developer hacking…

System calls are used to enable user processes to interact with the kernel However, to understand their importance, you must first learn how the kernel maps processes. The word length of the CPU determines the maximum size of the address space that can be managed, eg on 32-bit systems, there are 2^32 bytes while 64-bit machines can manage 2^64 bytes of address space. The maximum size of the address space isn’t related to the physical RAM on the computer and is therefore known as the virtual address space. Linux divides virtual address space into two parts known as kernel space and userspace. This division is based on an architecture-specific value. The key difference between userspace and kernel space is that access to the latter is forbidden to the former. Instead,…

The Linux kernel supports more than four dozen filesystems including disk-based filesystems (ext3/4, FAT32 and NTFS etc), virtual filesystems (/proc), and network filesystems (CIFS, NFS etc). To support the filesystems, the Linux kernel includes a layer between user processes and the filesystem implementation. This layer is known as the Virtual File System (VFS) and provides abstract data structures to represent files and inodes. One of the tasks of the VFS is to provide a uniform mechanism for manipulating files, directories, and other objects. It ensures that the real filesystems must fill in the data structures such that applications can use the same interface to access and manipulate files without knowing what physical or logical system the file resides on. For this purpose, it relies on the Device Independent Interface module…

A little known fact is that in August of 1994 Murdock received an email from one Marc Ewing saying that he was starting a company called Red Hat (you may have heard of them) that was going to build a commercial product. So impressed with Debian was he that he planned to use it as the base for this new financially-motivated distro. Of course, things didn’t work out this, but Red Hat Linux nonetheless became the last of the ‘Big Three’ grandaddy distros—those from which most others were derived. The name comes from a Cornell University lacrosse hat, given him by his grandfather, which Ewing had worn during his time at Carnegie Mellon. In 1993, Bob Young formed a business, ACC, which sold, amongst other things, Linux CDs and software.…

We’ve seen that in the early days, the distro was very much something that wanted to make your life easier. The first ones probably didn’t seem like they actually did that, but the huge popularity of Linux distros by the late 90s definitely suggests that they had become much nicer to work with, either that or they were just so useful that people had no choice but to work with them. Lately though, things seem to be changing. A small but interesting thing happened in 2014 when Gnome 3.12 was released. Or rather it didn’t happen. Gnome 3.12 represented a major advance for the desktop; all manner of problems in 3.10 had been corrected. It was generally considered to be the first of the Gnome 3 series in which the…

The are two types of people: those whose first kernel compiled and booted correctly and those who tell the truth. It can take a few tries to get it right, look at the sub-version number on distro releases, but you cannot break your system. This is because installing a new kernel version doesn’t touch your old kernel, and your Grub menu will contain all the kernels it finds in /boot. So experiment away knowing you have a safety net. The most common failures, especially if you are not using an initramfs, are not including essential items like your hard disk controller and root filesystem type as built-ins. Remember, you cannot load any modules until the root filesystem is mounted. The usual sign of a failure is a kernel panic, the…

You have to pity the poor blighters tasked with putting together ‘end of year review’ editions of magazines and news programmes when it comes to 2016. From David Bowie to Brexit and beyond, this year has been relentless in throwing up newsworthy events (tragically so, in some cases of course). While I’m loathe to get political in this column (you can get in touch with me on twitter via @Eddie_Catflap for that kind of thing) I found the aftermath of the EU referendum fascinating, particularly the changing fortunes of the key figures involved. One day you’re the Prime Minister and the next you’re on the backbenches; one moment you’re Lord Chancellor and Secretary of State for Justice ready to sweep into power and the next your so-called allies avoid you…

I’ve concentrated on MirageOS here which has garnered the most publicity in this relatively new market, but a look at the projects page on http://unikernel.org shows quite a few options available. The production supporting sysadmin side of me reels in horror at words like ‘early performance analysis’ and ‘research prototype’ however! MirageOS does have the momentum at the moment with its growing list of modules, but it isn’t the only game in town. There’s also rumpkernel (http://rumpkernel.org) which take a slightly different tack (the name is going to be a hard sell for any marketers though). Rather than go down the clean slate route, the rumprun unikernel targets software which runs on current operating systems like our beloved Linux. The project says it optionally supports a Posix-like application interface and…

Our expert Les Pounder travels the UK helping the Raspberry Pi Foundation deliver its Picademy teacher training, specialising in Maker Skills. He writes up his adventures at http://bigl.es School children are introduced to coding through a series of applications but the underlying computer science and logic will be the same no matter the language or application. One of the first skills taught is understanding the principle of the algorithm, a sequence of code that works line by line to complete a task. In Scratch we build this block by block, in Python we do this with every line of code written. But how can we make this more fun? Well, this looks like a job for Turtle—and no it’s not a ninja. For this project you only need any model…

Our expert Nate Drake is a freelance tech journalist specialising in cybersecurity. His dead man’s switch asks his long-suffering girlfriend to remember to water his rubber plants if he disappears. Did you have the misfortune to sit through Superman IV: A Quest for Peace? If so, you’ll remember a scene where the Man of Steel is forced to stop a subway train that has shot off down a tunnel. After single-handedly halting the train and saving everyone on board, Superman takes the time to reassure the public that the subway system is one of the safest ways to travel. This is in fact true, because while the fictional Metropolis may not make use of them, real-life subway trains have a dead man’s switch—a control that has to be continually pressed…

Our expert Nick Peers finds xrandr an essential part of his Terminal armoury, given that many resolution settings are absent under Screen Display. Terminal Learn to set, add and mirror display resolutions with xrandr Xrandr is your best friend you’re looking for a way to manipulate your monitor’s display through the Terminal. It’s the command-line tool that gives you control over RandR (‘Resize and Rotate’), the protocol used for controlling the X Window desktop. RandR can be configured through the Screen Display Settings tool, but it’s limited in scope and as you’re about to discover, xrandr can do much more. Let’s dive straight in and see what xrandr can do. First, open the Terminal and type $ xrandr. This will list the following attributes: Screen 0 , a list of…

Our expert Alastair Jennings has been flying drones for the past four years and has recently started working towards getting a full commercial drone licence. Once qualified, he thinks he’ll be having too much fun to think about use it for any commercial jobs. Raspberry Pi Calibrate your Pi-powered drone using APM Planner 2.0 for Linux Last month, we showed you how to build your own drone [Features, p44 LXF214]. If you were lucky then once you’d fitted all the cables and powered up, you would have been able to enjoy your first flight. However, if you’ve found that your drone has a tendency to fly off in a random direction or doesn’t seem to respond in the way that you want then this month we’re going to take a…

Our expert Sean D. Conway had formal training in electronics and half a career spent in aviation, so he really knows where he is with implementing a GPS receiver on a Pi. Geolocation Install and configure a HAT to gain GPS support The Raspberry Pi opens up a host of technology opportunities to explore in its own right, but a HAT (Hardware Attached on Top) expands the quantity and type of input and output resources available for use by a Pi. In our case, a pairing of the Pi with an Adafruit Ultimate GPS HAT (http://bit.ly/GPSHAT4Pi) provides any technology explorer with the ability to delve into geopositioning satellite triangulation. The Adafruit website provides information to get the GPS HAT operational. However, while the guide will explain how to do each…

In order for a GPS receiver to produce accurate data, it requires a fix. The fix is obtained by receiving data from enough satellites (minimum four) to determine its location. The GPS HAT has an LED connected to the data output of the MT3339 to provide a fix status indication. If the LED blinks once a second, the receiver doesn’t have a fix. This may require moving the antenna to another location that provides an unobstructed line of sight to the sky. During testing our receiver failed to obtain a fix while located in the basement. Only after positioning the antenna on the second floor was a fix obtained. This is indicated by the LED blinking once every ten seconds.…

There are many tracing tools for Linux including DTrace, perf_events, SystemTap, sysdig, strace and ftrace. SystemTap is the most powerful tool of all but LTTng comes close, apart from the fact that it doesn’t offer an easy way to do in-kernel programming. DTrace is in an experimental state on the Linux platform, its biggest advantage is that it also works on other Unix platforms including Solaris and Mac OS X. Alternatively, perf_events can solve many issues and is relatively safe to use and as a result it is very good for amateur users who don’t need to control everything on a Linux machine. Built into the Linux kernel, ftrace has many capabilities but doesn’t offer in-kernel programming, which means that you’ll have to post-process its output. LTTng has the lowest…

Our expert Mihalis Tsoukalos (@mactsouk) has an M.Sc. in IT from UCL and a B.Sc. in Mathematics. He’s a DB-admining, software-coding, Unix-using, mathematical machine. You can reach him at www.mtsoukalos.eu. Redis (REmote Dictionary Service) is a NoSQLkey-value data store, or more precisely a data structure server. Although Redis is similar to Memcached in functionality, it differs from Memcached because Redisis persistent, which means that data is saved on your hard disk, and supports more data types. Redis stores its entire data set in RAM, so it is extremely fast. The latest major version of Redis has support for clustering, which allows Redisto scale better. In this tutorial, we’ll look at Redis installation and usage as well as Redis data types. Then, we’ll examine an example in Python and talk about…

The people who develop Redis strongly suggest running production Redis servers on Linux because the Linux platform is where they do most of the Redis development and testing. However, Redis also runs on Mac OS X, FreeBSD and OpenBSD. As you already know, Redis can replace Memcached and can be used for caching operations. Redis is also really good at storing frequently-updated real-time data. The interesting thing is that it handles writes faster than it handles reads, so if you know you are going to have lots of write operations, you should consider using Redis. Additionally, the data types supported by Redis will make your life easier if they suit your needs. However, if a traditional database, such as MySQLor PostgreSQLdoes your job, don’t consider replacing it with Redis. The…

Both advantages and disadvantages of threads lie in their lightness—is it always the right solution to a problem? The main advantage of threads is that creating one or more threads has almost no overhead—conversely, creating a new process has a considerable overhead as it requires the duplication of the entire parent process. Additionally, threads can have control over threads of the same process while processes can only control their child processes. The biggest disadvantage of threads is that you will need to write extra code for dealing with their synchronisation in case threads must be synchronised in order to solve a problem.…

1 Update from DVD Q I have recently installed Ubuntu Studio 16.04 and I have heard that it is possible to add extra software from discs of other versions of Ubuntu. I have burnt the ISO of Kubuntu 16.04 from the LXF212 cover disc to a DVD, but how do I use this to add software to Ubuntu Studio? Susan Springfield A Sorry, what you are asking isn’t possible. There are two main ways in which distro installer discs work: The traditional way was for the disc to contain a collection of software packages and an installer. During installation, you selected the packages you wanted and they were installed. When distros started producing installable live discs, they had to come up with a different approach. The live disc contains a…

“The rise in smart internet-connected IoT devices has seen a corresponding increase in malware that targets them.” Security firm, Kaspersky recently released its DDoS Intelligence Report for the second quarter of 2016, and it makes for uncomfortable reading for Linux users. In the report (which can be read in full at http://bit.ly/DDosQ22016), it shows that 70.2% of DDoS (Distributed Denial of Service) attacks detected by Kaspersky’s DDoS Intelligence system (which analyses commands sent to bots from command and control servers) were launched from Linux botnets, which is almost double the amount discovered in the first quarter of 2016. Because Linux tools are considered the most effective for the SYN flood method of launching a DDoS attack, the rise of SYN flood attacks has also seen an increase. This type of…

Linux’s market share of desktop operating systems continues to rise. Only last month we brought you the good news that Linux’s market share hit 2% for the first time, and now, according to Net Market Share’s latest report (http://bit.ly/OSMarketshareLinux), this has risen once again to 2.33%, above Microsoft’s maligned Windows 8 and Windows Vista operating systems (which have a 2.09% and 1.22% market share respectively), and not too far off Mac OS X 10.11’s 4.69% share. It’s still an upward battle to close the gap with the most popular Windows version (such as Windows 7, with 47.01% of the market), but Microsoft’s recent aggressive practises to get people to upgrade to Windows 10 may end up pushing people to jump to Linux. The future of embedded Linux in smart vehicles…

Deepout Regarding your review of the Deepin 15 distribution in the March issue [LXF208], I have a few thoughts. Let’s see: “Developed in China…” With its nationally sponsored and encouraged intrusion of western computers? "Insists that you not run it in a virtual environment ... you can’t create an encrypted home folder...” Thanks all the same, folks, but I think I’ll pass on this distro. Too many red flags. Sometimes, our paranoia may not be misplaced. Bob Blum Annapolis, MD USA Neil says: Ha, can’t really blame you… Debian don’t You may imagine my intense interest in examining the various faces of Debian (the Daddy) using my LXFDVD. What a disappointment! It seems that Debian hadn’t considered the possibility that an English speaker (a born and bred Brit living in…

PyCon UK 2016 There’s still time to get your tickets for PyCon UK. Set over four days from September 15 to 19 at Cardiff City Hall, the event is a mix of workshops, talks, sprints and presentations all with a Pythonic twist. Expect to see lots of Raspberry Pi, micro:bit and, of course, Python-powered projects at this event. PyCon UK has also successfully integrated an education track for teachers wanting to usePython in the classroom. Tickets and more details are on the official website. http://2016.pyconuk.org Over The Air 2016 November 25-26, sees St John’s Church, Hoxton, London play host to two-day conference for those interested in mobile development. This event offers the chance to work together during a hackathon, learn from peers in workshops and listen to inspirational lightning talks.…

We’ve already touched on this subject a little in the regard toSkrooge’s colourful and versatile reports that look really good. But it doesn’t mean that reports in GnuCashor KMyMoney are lacklustre in comparison. There are 11 categories of reports in KMyMoney that cover almost any aspect of transactions, such as cash flows, budget, forecasting, taxes and much more. Graphs and various kinds of charts also exist for a more visual presentation and all reports can be exported to CSV or HTML. In GnuCash there’s a dedicated Reports menu with plenty of report templates divided into sections, such as budget, assets, income & expenses and business etc. Each submenu stores a respectable number of reports of many types. Most of them are formatted XML files and they look somewhat enterprise-like, although…

1991 AUGUST 25 August 1991 Linus announces his hobby project on comp.os.minix Linus Torvalds, a 21-year-old student at the University of Helsinki, Finland, starts toying with the idea of creating his own clone of the Minix OS. He originally intended to call his kernel Freax. However, when he uploaded the first version of the kernel, the maintainer of the FTP server, Ari Lemmke, renamed the directory that housed the source to Linux. SEPTEMBER 17 September 1991 v0.01 posted on ftp.funet.fi This release includes Bash v1.08andGCC v1.40. At this time, the source-only OS is free of any Minix code and has a multi-threaded file system. Torvalds also famously mentions that Linux currently isn’t portable and “It probably never will support anything other than AT-hard disks, as that’s all I have.” OCTOBER…

Managing and scheduling processes is one of the most important subsystems of the Linux kernel. Its purpose is to control access to the computer’s processors. Linux can run several processes at the same time despite the fact that a single-processor system can only run one process at any given time. To be able to multitask, Linux must switch repeatedly between multiple processes running on the system in rapid intervals. To multitask successfully, the kernel must decide how much time to devote to each process and when to switch to the next one. Also when it switches from one process to another, it must ensure the execution environment is exactly the same as it was when it last withdrew processor resources. Both these tasks are the responsibility of the scheduler subsystem.…

The objective of the network subsystem is to allow Linux systems to connect to other computers over a network. Thanks to it, processes can access the network without necessarily knowing what physical devices or protocols are being used. It’s architecturally modelled after the network protocols themselves. The reference model that defines a network is made up of seven layers and is known as the Open Systems Interconnection (OSI) model. However, most communication over the internet is based on an alternate model which combines some of the OSI layers into a total of four layers and is known as the TCP/IP reference model. At the bottom is the host-to-host layer that’s implemented by the device drivers for the network cards. Next up is the Internet layer which assigns unique addresses to…

Package management in Slackware is done through the pkgtools suite which includes self-explanatory commands such as installpkg , removepkg , upgradepkg , among others. A common complaint is that unlike almost any other modern package manager that you’d care to name, Slackware’s does not automatically resolve dependencies. We’ve already seen that this was commonplace in the early days, but for many users this will seem like something that we shouldn’t have to put up with in the 21st century. But it all depends on your philosophy—Slack users like to be in control, and they don’t necessarily feel that they are in control when they are asked to install one package (presumably one they know about, because why would a Slackware user install something without knowing all about it?) and all…

After spending some time getting your customised kernel just the way that you want it, that annoying Linus Torvalds guy goes and releases a new version. You’re probably thinking that you’ll have to start all over again, right? Actually, you don’t. You’ll need to download and unpack the new sources. Apply any patches you want, bearing in mind that some may fail because you may need a new patch or even none at all as it’s now in the kernel. Next cd into the source directory, copy your old .config file into it (there will be a copy in /boot and also in /proc if you set that option) and run $ make oldconfig . This command compares your existing.config with the options available in the new Linux kernel version…

“Gimp boasts modern split preview for GEGLenabled filters.” The new generation of Linux users are likely to be unaware of what the GTK toolkit’s name stands for. Many years ago, it was written specifically for the Gimp image editor and was known as the Gimp ToolKit. Gimp was one of the first bold and feature-rich graphical Linux applications, and its interface library later grew into the core part of many desktop environments, such as Gnome and Cinnamon etc. Gimp doesn’t often supply new and fresh releases, but when it does the list of changes is always thrilling and amazing. The 2.9.4 version is a major milestone and a significant leap forward since the 2.9.2 release [which we proudly covered in LXF207]. The first thing you’ll notice is the new tool…

“An indispensable helping hand for students and web developers.” Many students use standard calculator applications, which work nearly the same across all platforms. Apart from advanced mode – commonly called engineer/ scientific mode – calculators lack the intelligence to solve mathematical problems. The NaSC project is an attempt to plug this particular gap. There are many things that the NASC acronym can refer to, but the point of interest for us is the tiny and nifty open source application. NaSC works like a normal calculator, although it’s focused on text input. Its main panel has numbered lines, just like an advanced text editor. You can simply put random text strings here, but once NaSC detects a solvable task, problem or equation, it will automatically solve it and display the answer…

Hard to believe it’s now a little over four years since I first got my hands on a Raspberry Pi. In that time I’ve taught myself Python, learnt to solder, gained an understanding of electronics and robotics and taken part in Pi Wars (the Raspberry Pi robot competition—I came a respectable fourth). I’ve also become a member of Cheltenham Hackspace, a volunteer at Cotswold Rasperry Pi Jam and met a whole bunch of extremely nice, positive people along the way. Educated by Pi I’ve always been slightly more than ‘a bit of a geek’ but the Pi opened up a whole new world of coding and hackery. I went to a pretty poor school full of overwhelmed and under-inspiring teachers – except for one teacher called Mr Glazier. He instilled…

Why bother using Turtle? Well, quite simply, it’s a great introduction to Python because it offers something familiar to children. Scratch and LOGO both offer a similar tool to help children understand how a sequence of code works, but Turtle is also a great activity to introduce all aspects of coding, such as sequence, iteration, selection and decomposition are all key concepts that can be demonstrated with Turtle. In fact Turtle is a great introduction to robotics, with the turtle representing the robot. Once children understand how to move the turtle, they can control a real bot. I used a whiteboard on the floor, modelling clay and a whiteboard marker to demonstrate real-life turtle with a Pi robot.…

1 Create a switch script In your Pi’s home folder, type nano switch.sh to create a file. Next paste in the script from the tutorial. (You may want to comment out lines to invoke FTP/e-mail scripts.) When you’re done use Ctrl+x to quit, save, then run chmod a+x script.sh to execute the switch. 2 Schedule a cron job Simply run crontab -e to open the Cron scheduling utility which will act as our countdown timer. Choose Option 2 to edit using nano and at the very bottom of the file paste 0 0 * * * /home/pi/switch.sh/ . Use Ctrl+X to exit, saving your changes. 3 Create a reset switch Type nano reset-switch.sh and paste in: #! /bin/bash touch /home/pi/switch.sh Exit and type chmod a+x reset-switch.sh to make the reset…

If you want to make your edits permanent, you’ll need to edit some config files. The standard way of doing this is using xorg.conf, but it can be quite fiddly. If you’re looking for a fast and dirty way of changing screen resolution, and are happy to accept that it’ll affect the screen only after you log on as your user account do $ nano ~./.xprofile . Ignore the error, and this should generate an empty, hidden file called xprofile. Type your commands into the file as if you’re entering them into the Terminal, one per line. The following example creates and applies a new resolution setting on boot: Press Ctrl+o to save the file, then Ctrl+x to exit. The file needs to be executable, so use: $ sudo chmod…

After quite a bit of work your drone should now be at the flying stage and with a bit of practice and quite a few replacement propellers you should have your creation airborne. Don’t worry if it takes a while to get to grips with the controlling this drone as at present it’s about as raw as it gets and lacks any of the niceties of the expensive commercial drones you can by on the high street. Just because you built the drone yourself it doesn’t means that you can’t rely on a few of the more advanced features to help stabilise flight and make the whole flying experience a little easier. The first essential is to fit GPS. The cheapest option is to purchase the GPS unit at the…

GPS satellites send information about their location and time in data sentences, but in order for a GPS receiver to retrieve the information the signal must of a specific strength for a specific duration. If the signal is degraded because of obstructions while your receiver is trying to get a fix, the data is lost and the unit must start over. To assist GPS units in locating satellites, the manufacturers make available ephemeris data from their FTP sites. The data can be downloaded and then uploaded into the GPS unit’s flash memory. Then, when the GPS unit starts, its has information on the satellites that assists it in establishing time to first fix (TTFF) more quickly.…

BabelTrace is a tool that helps you deal with various trace files, including the trace files generated by LTTng. It allows you to read, write and convert trace files using the Common Trace Format (CTF) and is very useful for presenting CTF files onscreen. If BabelTrace isn’t already installed, you can get it with: The babeltrace-log utility that comes with the babeltrace package enables you to convert from a text log to CTF but you will not need it if you are only dealing with LTTng. You can learn more about babeltrace at http://diamon.org/babeltrace. You could also try using Trace Compass (http://tracecompass.org) to view LTTng trace files, which is a graphical application. You can also learn more about the CTF format at http://diamon.org/ctf.…

Redis has two unique characteristics: it runs in memory and it supports many unusual data types. One of the benefits of Redis running in memory is that it’s really fast! This can be proven by the fact that most operations on Redis data types have a time complexity of O(1), which is a constant time regardless of the amount of data stored in the Redis database. Additionally, the data types supported by Redis offer unique design capabilities to the developer. Redisis better than Memcached because Redis offers built-in persistence. Redis requires you to think in a different and a more contemporary way when designing applications, which can give a new perspective to your applications, and adds support for clusters, which makes it scalable. Finally, Redis uses a simple configuration file,…

Our expert Mihalis Tsoukalos (@mactsouk) has an M.Sc. in IT from UCL and a B.Sc. in Mathematics. He’s a DB-admining, software-coding, Unix-using, mathematical machine. You can reach him at www.mtsoukalos.eu. Developing concurrent applications is a difficult subject and threads are the root of many nasty bugs, so you should try to make your applications as simple as possible. However, threads allow you to use your CPU, including its various cores, to its full potential. How processes, threads and variables are related can be seen in the diagram (pictured below). As you’ll see a thread can access two kinds of variables: local and global ones. This article will use both Python versions—you can find out which Python version is used by looking at the first line of a Python script; for…

Strictly speaking, a thread is a subset of a process that is being executed within the context of a process and shares the same resources given to the process by the kernel. A thread is the smallest unit of execution schedulable by the process scheduler of the OS. Each process starts with a single thread but it’s allowed to create additional threads. This means that when a process creates a thread, apart from its own flow of control and stack, a thread shares everything with the process that originally created it, such as global data and other resources, as well as file descriptors and the current working directory. So, strictly speaking, you can’t really consider threads to be autonomous entities.…