Linux User & DeveloperNo. 170的目錄

This issue » Virtualise your system » 50 terminal tricks » Use a phone as a smart home server » Back up your data securely Welcome to the latest issue of Linux User & Developer, the UK and America’s favourite Linux and open source magazine. How many computers do you have in your home? The answer, given the rise of smartphones, tablets and laptop/tablet hybrids, is probably “A lot more than ten years ago” – and that’s not including games consoles. Where once a single PC would serve the needs of the entire family, now it’s more likely that everyone has their own device. Those laptops and desktops can, however, include more than one operating system, whether that’s a lightweight install to allow you to skip smoothly from OS to…

“EOMA68 boasts support for a wide range of distros, including CentOS, Debian, Fedora and Arch Linux” Manufacturing desktop computing parts isn’t overly good for the environment, so it’s no wonder Rhombus Tech’s ‘earth-friendly’ desktop computer has already garnered a lot of support. The EOMA68 computing devices offer an alternative stance to the classic computing platform, using a standardised PC board alongside a series of 3D printable housing parts. At the time of writing, UK startup Rhombus Tech has raised nearly 75 per cent of its $150,000 crowdfunding goal, but with a number of days of left, it’s likely it’ll far exceed its original target. The company has developed what it’s touting as an ‘earthfriendly’ computer, which relies on easily attainable materials that have little impact on the environment. Another key…

A bug within Linux’s transmission control protocol, used primarily when browsing the internet on unsecured connections, has potentially left 1.4 billion Android users at risk. Security giant Lookout has discovered that nearly 8 out of 10 Android devices are potentially at risk, adding that the fault in the TCP has potentially enabled hackers to hijack internet traffic and modify connections. In the long run, it can mean your smartphone is taken over by snoopers, and your sensitive data can be manipulated and used. Data of this nature should always be put behind some sort of encryption, and now is a good time to do so if you haven’t already. While at the time of writing there’s no known fix for the issue, it’s believed that a fix will come from…

To keep each Formula Pi race as fair as possible, each competitor will be racing with the same YetiBorg HS Zero robot. Each robot is carefully crafted to take all the bumps and scrapes involved with racing, with each one coming with everything the competitor needs, bar a 9V battery and a Raspberry Pi Zero. The casing of each robot is constructed from a 2mm thick aluminium and powered by a 60rpm 6V 220ma motor. For racers, this should mean that the YeitBorg can reach some pretty nifty speeds. The rest of the robot is within the racer’s hands, and it’s up to them how they want to improve the robot. Each robot must be constructed themselves and Formula Pi supplies the necessary code to make the robot completely autonomous.…

Whether you’re running Ubuntu and Fedora on a dual-boot system, or you’ve got a partition for Windows as well (you might even run a Hackintosh partition too), then you have a definite issue with your setup: rebooting. It can take time to reboot; from shutdown, to your GRUB 2 menu selection, and then booting into the chosen OS can take as long as 5-10 minutes – time better spent being productive rather than staring at a screen. When you consider the number of times that you need to swap operating systems purely to grab a single file, or input just one command, it’s all a bit clunky, really. With a virtual machine, however, you overcome this problem. The alternative operating system exists as software (a ‘guest OS’) that you can…

Visual Studio Code provides embedded Git control for standard client actions. It also has built-in debugging support for the Node.js runtime Resources Fedorainstallation instructions for.NET Core microsoft.com/net/ core#fedora Visual Studio Code code.visualstudio.com C# Extension for Visual Studio Code code.visualstudio.com/docs/languages/csharp Microsoft has released an open source, modularised form of the .NET technology base called .NET Core that is cross-platform and offers support for a variety of Linux distros. The companion, .NET Core SDK, provides the command-line tooling to create simple .NET scaffold code, download project dependencies, compile, package and publish. However, to fulfil the story of .NET Core development on Linux, you need an editor that can support the iterative code-edit-debug cycle. Enter Visual Studio Code, a rich, cross-platform editor that is highly extensible, supports several programming languages, includes a debugger…

One risk of keeping all your data on local machines is that your local system could be damaged and you will lose your data Resources Types of backup http://typesofbackup.com/ Data backup types explained bit.ly/16uRkcS Backup virtual servers with traditional techniques and specialised tools bit.ly/2bjeczS Backup typically refers to the process of copying and archiving data: the idea is to enable a system administrator to restore the data if there is a data loss event. You can consider backup as a simple form of disaster recovery, but please note that it should not be considered as a complete disaster recovery process. One risk of keeping all your data on local machines is that in case of a natural disaster, fire or flood, your local system could be damaged and you will…

>_006 Read the system log Unix collects a large amount of data as it runs. Most of it is found in the syslog, whose last lines can be emitted into the terminal via the tailcommand. >_007 Determine your system temperatures Notebooks, desktop PCs and workstations come with a plethora of sensors. Entering the sensors command emits a list of all sensors visible. If the relevant packet is not yet installed, the shell will, instead, guide you through the installation process. The code accompanying this step shows the output from our ThinkPad T430. >_008 Learn to apply advanced temperature-checking techniques Today’s GPUs can easily sink more energy than the CPU driving them. Should you suspect cooling issues on your GPU (or an adverse affect to that expensive GPIB router card in…

Given the tremendous power of the command line, developers and users might feel like controlling a computer remotely via a command line. This is made easy due to the relatively low resource demands – being text-based, streaming a command line works even over a throttled mobile connection. Initially, Unix workstations were accessed via Telnet. SSH – the abbreviation stands for ‘Secure SHell’ – is a more secure version of the protocol, which foregoes simple plain-text transfers for a more or less efficient form of encryption. Get connected Configuring the local SSH daemon depends from workstation to workstation: defer to Google to learn more. Connecting to an instance is really easy – the bickering about the host key can be ignored in most cases: Stay alive By tradition, a job started…

While the main part of the article is about querying Google Calendar to pull event details to populate a family calendar display, there is nothing stopping you from working in the other direction and updating the remote calendar based on what happens at the monitor. This way, you can keep yourself synchronised with what is happening back home. The first thing you might want to be able to do is to add a new event to a calendar. While there is an 'insert' method, it is probably overkill for such a simple application. For your family calendar, you probably just want to use the 'quickAdd' method. Let's say that you need to actually update an existing event. As an example let's say you got the time wrong on the above…

There are many competing desktops out there, even in the niche of lightweight, low system-resource use, and some even get their own version of Ubuntu built around them. So what does Lumina have that separates it from the rest? Most desktop environments use various operating system frameworks to work with the system, but Lumina eschews DBUS, policykit, consolekit, systemd and HALD, using its own built-in interface layer. Written from scratch in C++ for speed it has very few dependencies for a full desktop environment, leaning only slightly on Fluxbox for a few accessories. Installation is easy for most distros, as repos are available with the latest binaries, but building from source is not a problem, with build dependency installation a single operation on Debian and Fedora-based distros. The default appearance…

Welcome to the Linux User & Developer DVD. Run dozens of distros on one machine with our complete virtualisation toolkit. From backing up data to running virtual machines to the best selection of lightweight distros, this kit has got everything you need to transform your PC into a virtualised powerhouse today! Featured software: Lubuntu The objective of the Lubuntu project is to create a variant of Ubuntu that is lighter, less resource-hungry and more energy-efficient by using lightweight applications and LXDE, the Lightweight X11 Desktop Environment, as its default GUI. Debian Debian is a classic Linux distro that’s been running since 1993. It’s a great introduction to Linux as well as being powerful enough for pro users. With support for a vast range of hardware and a complete collection of…

As far as scripting languages go, Microsoft’s PowerShell is considered one of the best. It’s an ideal piece of kit to have around for running and managing system tasks with ease, and is also perfect for those who are looking for something built on the .NET framework. Microsoft has teased the release of PowerShell over on Linux for a while, so it’s great to see that the command-line shell has finally gone open source. With Microsoft’s ‘multiplatform’ dream in full flow, we are likely to see many of its other core software tools eventually make the full transition across to Linux. The codebase for PowerShell will work across all compatible, open source OSes, and will be readily available with a license on GitHub. It’s important to note that this initial…

Top 10 This month Stable releases (16) In development (10) Mint is definitely the flavour of the month currently, and it’s one of the few months we’ve encountered that we haven’t seen any major Ubuntu-based distro releases. Highlights Mint Mint has been steadily growing its userbase over the past few months, and it’s still gaining support thanks to its most recent update. Make sure to give it a download if you haven’t done so already. Elementary Elementary is one of the few distros to gain users this month, but we’re not surprised. It’s still one of the prettiest distributions out there, with some nice graphic enhancements also on board. Arch Arch may have fallen out of favour with people, but there’s some fantastic spin-off distros out there that look to…

Each competitor will receive the standard race code, manufactured by the Formula Pi team, which has to be used within their robot. However, it’s up to the competitor to explore the ways they can adapt the code to help improve how their robot performs in a race. Essentially these changes can be as simple or as advanced as you see fit. For example, some may want to alter the code to help their robot react better when navigating corners, while others may want to improve how the robot makes decisions when going around the track. What we’re most impressed with is the control that each racer has over their robot’s motors. One particular section of the script relates solely to the motor speeds, and it’ll be up to the competitor…

LINUX MINT If you haven’t already tried Linux Mint (it tends to be unfriendly with certain hardware) then installing it in a VM is a great idea, as the desktop doesn’t require 3D acceleration. This makes it ideal not just for hardware virtualisation, but lower-spec systems without this feature as well. LUBUNTU This ultra lightweight version of Ubuntu is ideal for running on virtual machines. Its modest footprint on system resources means that you can get the most out of it, giving you an idea of how it might run on an older PC or laptop when installed as a full operating system. SLACKWARE Yet to sample the lightweight, simple Slackware? Ideal for advanced Linux users (largely thanks to its closeness to Unix), Slackware runs effortlessly with all virtual machine…

Using the right tools for the job is just as important with virtualisation as it is with any other task. For instance, should you wish to virtualise an ARM device like the Raspberry Pi, VirtualBox will prove useless, as it is designed for 32-bit and 64-bit virtualisation. For ARM device virtualisation, you need QEMU, which is also capable of providing virtual machines for 32-bit and 64-bit platforms.This isn’t just about the Raspberry Pi, however, as almost any distro or operating system can be set up and run in QEMU – once you’ve mastered its command-line interface… 01 Install QEMU If it’s not installed already, update your Linux repos, before installing the QEMU package, using the command line. For Ubuntu, this will be: RedHat/Fedora users, go with: SUSE/openSUSE uses: If you’re…

What we’ve shown you so far is really just the simple stuff when it comes to virtualisation in Linux. Whether you’re using VirtualBox, QEMU, KVM or any of the proprietary alternatives, virtualisation is a tool that works in many different ways, with a myriad of options for each operating system out there. For instance, we’ve alluded to the fact that ARM devices such as the Raspberry Pi can be virtualised using QEMU. Configuration and installation can be tricky, but it is possible, enabling you to install Raspbian and other Pi-centric distros on your desktop PC (although a lack of GPIO will limit the possibilities). Additionally, you may want to run a virtual machine based on Mac OS X. Remarkably, this is possible, and while it was previously limited to VMware…

Resources Tasker bit.ly/1i0IuDw IFTTT ifttt.com SL4A bit.ly/2byqjtf Busybox busybox.net/ Ulti Server bit.ly/19UzN8w TeamViewer QuickSupport bit.ly/1clagJQ IP Webcam bit.ly/1KqZpyq Kodi bit.ly/1G8mSQg joaomgcd bit.ly/2bcKHBu Vodafone Smart Prime 6 bit.ly/2aZeaer An Android phone makes a surprisingly good smart home server. Even a relatively old device will have a decent amount of storage, Wi-Fi connectivity, lots of sensors and, best of all, use a minimal amount of power. From a software perspective, Android is hugely flexible. As well as the option of using trigger/action-based applications such as Tasker, Android – with its Linux base – can use traditional command-line scripts. One of the benefits of building your own home automation system (so far as is possible) using a dedicated device is that you have a lot…

Resources A text editor such as Emacs or vi The Go compiler Concurrent programming is a difficult area of computing that requires special care and precision. This tutorial will talk about concurrent programming in Go, which introduces a unique approach to concurrency. Go uses goroutines and channels in order to program concurrent applications but can also support traditional concurrency techniques. Everything in Go is executed using goroutines; when a program starts its execution, its single goroutine automatically calls the main function in order to begin the actual execution of the program. This tutorial will mostly talk about goroutines and channels. However, Go also supports the traditional and well-known concurrency model that uses shared memory. The next tutorial is the Go series will continue talking about concurrent programming in Go so…

>_010 What’s in a name? Should you ever wonder about the role of a specific command, entering whatis followed by the name of the command in question tends to lead to further information on the topic. Our example, shown here, tells us what the gcc tool is all about. >_011 Simple help Most shell commands come with an integrated help system providing further information about the syntax. It can usually be accessed by passing in a parameter like -help, --help, -? or --?. If the syntax is not correct, the utility will usually show a little message informing you about the correct help parameter. Be aware that experimenting around with these commands can be dangerous: we would not try to find out the correct help parameter for rm or similar…

>_033 Get file information Sometimes you simply want to see what is contained in a text file. In that case, invoking the more command is helpful – it shows one screen-full’s worth of content, which can furthermore be scrolled down effortlessly. >_034 Keep an eye on changes Tools such as the sensor utility are best watched as time goes by. This can be accomplished by prefixing it with the watch command, which runs the specified command repeatedly. The tool can even be provided with the parameter -n, which allows you to configure the delay between the individual updates. >_035 Find your current location Even though Bash usually does a quite decent job at displaying the current path, some special folders are not displayed in full. This problem can be addressed…

CMus bit.ly/2bSc9n9 Friends of the vi editor can use their well-liked syntax to perform media playback. Deploy CMus to get your hands on a nicely designed media player which behaves just like vim. People who dislike vim are unlikely to be happy with the product, though – if you don’t know vim by heart, another media player with a simpler user interface is likely to leave you happier in the end. mp3blaster mp3blaster.sourceforge.net If CMus is intended for vim heads, mp3blaster is the MP3 player ‘for the rest of us’. Its super-easy user interface is full of hints, which explain the various keyboard shortcuts needed for multimedia manipulation. The developer claims that its design was inspired by traditional CD-ROM players – if you ever handled a CD-ROM, you will not…

What you’ll need • Raspberry Pi NoIR Camera V2 Element14.com • Raspberry Pi case with mount or slot for camera module • Portable power supply Want to get more out of your Raspberry Pi’s photographic abilities? You might have already connected a webcam or the official camera module, but found that certain activities – particularly shooting in low light – have been unsuccessful. The solution is a new camera module, the Raspberry Pi NoIR Camera Board, which has no infrared filter This makes the camera ideal for taking infrared photographs or photographing objects in low light (you still won’t be able to take photos in the dark without a light source). Capable of delivering 5MP still images, or recording video at 1080p and 30fps, the NoIR camera is easy to…

Live boot Insert the disc into your computer and reboot. You will need to make sure that your computer is set up to boot from disc FOSS Insert the disc into your computer and double-click on the icon or Launch Disc file to explore the contents Distros Distros can be live booted so that you can try a new operating system instantly without making permanent changes to your computer Explore Alternatively you can insert and run the disc to explore the interface and content Important information Check this before installing or using the disc For the purpose of this disclaimer statement the phrase ‘this disc’ refers to all software and resources supplied on the disc as well as the physical disc itself. You must agree to the following terms and…

1 CorePlus CorePlus is one of the smallest Linux distros, and ships with three very different variants. The smallest of the small is the Core edition, which uses just 10MB of resources, but lacks a window manager. It’s incredibly basic and does the absolute minimum you’d expect from a distro. 2 LXLE The lack of resources taken up by LXLE make it a sensible choice for those looking to breathe new life into an aging desktop machine. It’s tailored to work out of the box, but with plenty of customisations on hand as well to make it your own. 3 Porteous While Slackware-based distros have generally fallen out of favour, Porteous remains one of the best around. It’s designed for managing removable media through a series of modules, which help…

While the Surface 3 may have received plenty of critical success, it has by and large alienated Linux users wanting a solid piece of hardware. It has been plausible getting older versions of the Linux kernel working on the Surface series of tablets, but the process is, arguably, far more convoluted than it’s worth. However, that’s all about to change with the first release candidate of Linux 4.8. Built in to the release is a new driver, with noted support for the Surface 3 touchscreen controller. We should mention here that a lot can change between now and the emergence of the final release, so the driver may also be changed; it is however, a great inclusion for those seeking a new tablet. The $499 Surface 3 should run Linux…

“Where did the idea for Formula Pi come from? When I was young, my father used to take me to watch motor racing. While most people were obsessed with driving the cars or which celebrity the driver was, I always preferred the engineering behind the cars and how they were built. I always wondered what it would be like to take the driver away from the car, and have the cars compete among themselves. How cool is it to have a driver take their hands off the wheel? To have self-driving cars taking sick people to hospitals, for old people to visit their family even if they can’t see well, or to get me home from the “very occasional” pub evening! It was these ideas that eventually formed what we…

“Linus Torvalds announced the first few release-candidate kernels for what will, in a few more weeks, become 4.8. In his announcement mail for 4.8-rc1, he noted that he was a little behind in pulling in a handful of patches due to travel, but that he was closing the merge window to prevent any more patches coming in. According to Linus, 4.8 will be one of the “bigger releases lately”. Indeed, the feature set landing in the new kernel is quite impressive (read on for an initial summary), and overall the kernel includes a few changes that skew the stats in a lopsided fashion. For example, 4.8-rc2 was “dominated by arch updates, and fs/ and mm/” (rather than the typical driver-heavy focus after the initial rc1). And, in a further departure…

VirtualBox USEFUL FOR Versatile virtualisation. VirtualBox is capable of both software- and hardware-assisted virtualisation, making it the best all-round choice If you’ve had go at virtualisation in the past, the chances are that you used VirtualBox. It’s free, open source and available for all major operating systems, including Linux. With VirtualBox, you can easily run another Linux operating system, or even (if you’re desperate) install Windows, perhaps to run software that doesn’t perform well with Wine. VirtualBox does this by creating a virtualised hardware environment, which receives a nice performance boost if your system is already equipped for virtualisation. Meanwhile, VMs (virtual machines) are stored as disk images, making them easy to back up and migrate to other PCs and virtual machine applications. QEMU USEFUL FOR running a virtualised ARM…

“Given that Bash is Turing-complete, developers could – in theory – use ncurses or a similar library to create custom output” Resources Bash gnu.org/software/ bash Decades of hacker movies have ensured that Joe User has a dedicated bit of respect of all things Terminal. The Bash shell can be combined with a bunch of useful system commands to create nifty scripts dedicated to file system traversal. Given that Bash is Turing-complete, developers could – in theory – use ncurses or a similar library to create custom output. A more practical approach involves the invocation of dedicated programs that handle the selection process and return a result to the caller. As time went by, developers created a large variety of utilities that provide these features for you. Dialog is, by far,…

“Censys holds a huge amount of data that can be parsed by using its own search engine” Resources Zmap https://zmap.io/ Masscan http://bit.ly/1pSDGls Censys Database https://www.censys.io/ Censys API http://bit.ly/2bQpRVI Heartbleed bug http://heartbleed.com/ Heartbleed PoC exploit http://bit.ly/2bIKwMJ Scanning your network in search of well-known vulnerabilities is noisy and time-consuming. Although there are tools that can help you decrease the time it takes to scan an entire IPV4 network address space, such as Zmap and Masscan (covered in this tutorial), you should be aware of some freely available services that perform internet-wide scanning on a regular basis, exposing their results to anyone who cares to use them. This is precisely the case with Censys (see References). Censys holds a huge amount of data that can be parsed either by using its own search…

>_020 Search the package information The apt-get tool comes with a little brother called apt-cache. It can be used to find out information about the packages currently known in the cache, gathered from various repositories after apt-get update is run. One simple use case involves finding out more about the origins of a package. >_021 Sniff out dependencies When deploying packages on space-constrained systems, finding out more about dependencies is helpful. Simply enter apt-cache showpkg followed by the name of the package in order to dump detailed information on dependencies of the named packet. >_022 Clean up! As time goes by, apt-get can accumulate quite a bit of cached information. This can be removed by entering the command apt-getclean – be aware, though, that many systems don’t accumulate garbage. In…

>_029 Who owns what? The first step to successfully managing the permissions of files involves finding out who has what rights. Entering ls -l provides you with an expanded version of the normal ls output which also lists owner and accessibility permissions in the form of a table similar to the one shown in the image. Above Each character describes one bit of file system information >_030 Understanding the output As long as the width of the terminal is wide enough to take the entire output, ls generates classic tabular output. The eleven characters on the very left of each line provide information on the rights. After that, the two usernames provide information about the user and the group owning the file: groups are a very efficient way of sharing…

"You need to go to Google and enable the API beforehand" “For many people today, a major issue is keeping their time organised and keeping track of scheduled events. This gets compounded exponentially for every additional person that you need to keep track of. That includes children. This issue, we will look at how you can use a Raspberry Pi to display a family calendar and help you keep track of all of the events happening in the lives of your family members. Like the previous articles in this series, we will be focusing on the code you will need to get your calendar information. As for the actual physical display, there are many options you could choose. These include small HDMI displays or small screens that plug directly into…

What you’ll need • Article’s Github repository (https://github.com/alexellis/zumopi) • Explorer Robot as built in part two • Wi-Fi dongle • Ultrasonic sensor • 2x analog light sensors In part three we gave our robot “legs” through a manual control program and a gamepad. Now we will add self-driving capabilities through sensors and a feedback loop. We start off by looking at open versus closed loops for control, then create a simple obstacle-avoiding behaviour. Once our robot can avoid walls we will add a second behaviour to follow a light source such as a torch being shone at the left or right side of the robot. The programs are only a starting point for you to adapt and tailor to your needs. The light-following program could be adapted into a line-following…

The FriendFeed social media websitemayhavedisappeared beneath most peoples’ radars since Facebook bought it seven years ago, but its great legacy is the non-blocking Tornado Web framework. Designed to cope with thousands of simultaneous connections, its performance remains ahead of other Python frameworks like Django and it’s ideal for sites needing long-lived connections to users – perhaps for your customer support department’s new chat app? The HelloWorld app on GitHub is one of a number of demos which play to Tornado’s strengths and show you the possibilities from websockets to web spiders. Speaking of websockets, Tornado is just the thing if you’ve run up against the limitations of WSGI, which does not support non-blocking requests. Database support includes asynchronous drivers for MongoDB and PostgreSQL, and a choice of drivers for CouchDB.…

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