Linux FormatApril 2017的目錄

Jonni Bidwell Ctrl-R is much more useful than using the cursor keys to search your Bash history. Then there are the laconic curly brace expansions. It would be nice to understand the effect of putting slashes at the end of directory names in an rsync command too, but this is a secret that mere mortals cannot behold. Neil Bothwick Without a doubt it’s a terminal multiplexer like tmux or screen. Until you have tried using one of these, and got over the initial learning hump, you will never want to do without them. While I find that screen is the best known multiplexer, I find tmux is more capable and no harder to learn, so why not give it a try. Les Pounder For me it’s the handy && conditional…

GitLab is a popular and important resource for many companies and developers, such as Intel and Red Hat, so when at the end of January 2017 the service went offline for what the GitLab Status Twitter account called ‘emergency database maintenance’, many people were understandably concerned. A later tweet offered more clarification about the problem: “We accidentally deleted production data and might have to restore from backup.” Not a terribly reassuring message and, after six hours of downtime and concerns over data loss, a better picture of what happened started to emerge. A detailed blog post by GitLab (http://bit.ly/GitLabDBIncident) explained that the first incident occurred on January 31 at 6pm, when a number of spammers began attacking the database by creating snippets and making the database unstable. Troubleshooting began in…

“The infinitely customisable nature of Linux has resulted in its expanding footprint across industry sectors and world regions. Beyond the internet and data centres, it’s now found in devices such as Kindles, smart TVs, and even Tesla cars. Geography-wise, China is a country that has witnessed tremendous increase in Linux use. According to the 2012 IDC Worldwide Quarterly Server Tracker, Linux server market growth in China surged from 9.2 to 33.2% between 2002 and 2012—a rate surpassing the global average. And there are other telling signs. Tencent, one of the biggest tech companies in China and the world, was among the first to use the OpenDaylight Project’s Software Defined Networking controllers to manage its massive data flows. The Chinese government has even developed Ubuntu Kylin, a national Linux distro which,…

Find and join a LUG Alpinux, le LUG de Savoie Meet on the 1st and 3rd Thursday of the month at the Maison des Associations de Chambéry www.alpinux.org Bristol Hackspace Studio G11, 37 Philip Street, Bedminster, Bristol, UK, BS3 4EA http://bristol.hackspace.org.uk Cheltenham Hackspace The Runnings trading estate, Cheltenham. Thursday night from 7pm. www.cheltenhamhackspace.org Lancaster and Morecambe Makers Unit 5, Sharpes Mill, White Cross, Lancaster, Open Night on Wednesday evening 18:30pm till late. www.lamm.space Huddersfield Raspberry Jam Meet every 4th Saturday of the month at Huddersfield Library. Huddersfieldraspberryjam.co.uk Hull Raspberry Jam Every other month at Malet Lambert School, Hull. https://twitter.com/hullraspjam North Kent Raspberry Pi User Group Every two weeks at Medway Makers, 12 Dunlin Drive, St Mary’s Island, Chatham ME4 3JE https://nkrpug.wordpress.com/ Preston Hackspace Open night 2nd Monday of the month…

In brief... Socket: 1151 Cache: 3MB Type: 64-bit SSE: 4.1/4.2 Process: 14nm Cores: 2 Threads: 4 Clock: 3.6GHz TDP: 51W Max memory: 64GB DDR4 Channels: 2 (ECC) GPU: Intel HD Graphics 630 Clock: 350MHz Max: 1.1GHz Units: 24 OpenGL: 4.4 Displays: 3 Virtual: VT-x, VT-d, EPT The end of Intel’s CPU strategy as we know it seems very likely. We don’t mean that in an apocalyptic sense. Intel isn’t about to suffer an existential calamity. But AMD’s Ryzen processor is coming, and we’re confident it’s going to shake things up. That’s the context into which Intel’s Pentium G4600 arrives. Based on the latest Kaby Lake microarchitecture, it’s very much a child of the last five years or so, when Intel ruled on the high seas, across the land and up…

In the previous iteration of this Roundup, we included Qubes OS in the mix as well. While it is an interesting Linux distribution it’s more geared towards security conscious users rather than privacy advocates. The distro divides the computer into a series of virtual machines or domains using Xen that are cutoff from one another. Each virtual machine only has access to the services that it needs to perform the designated function, thus limiting the potential security threat. You can, if you so desired, deploy Whonix over a Qubes installation to get the best of both worlds. Another distro that’s worth looking at and that we covered before is Ubuntu Privacy Remix. It’s now called Discreete Linux and is currently in the early stages of development. One notable feature of…

The Linux command line offers various options to help you be more productive and find your way around the unfamiliar environment. For instance, many commands and utilities support a --help option that displays information about its supported options. For example, the rm --help command will print the various options supported by the rm command along with their description and brief usage instructions. Similarly, most command-line utilities also bundle a formal piece of documentation known as the manual page and usually referred to as its man page. The command man mkdir will bring up the man page for the mkdir utility. There are also a couple of helpful utilities that can extract brief information from a man page. For example, the whatis command displays a very brief description of a command…

The shell has various mechanisms to effectively create compressed archives and backup files. Archiving is the process of gathering up many files and bundling them together into a single large file. The tarprogram is the classic tool for archiving files, e.g. the command tar cvf documents.tar Documents/ would archive the whole Documents directory inside a single file called documents.tar. Conversely, tar xvf /path/to/documents.tar will extract the contents of the archive under the current directory. Once you’ve created an archive, you can also compress it before backing it up. The gzip program is used to compress one or more files. When executed, it replaces the original file with a compressed version of the original. The corresponding gunzipprogram is used to restore compressed files to their original, uncompressed form. The bzip2 program…

Sage advice for your journey to master-level command-line Jedi: 1 screen If you SSH into remote machine regularly, you’ll find screento be a wonderful companion. Using the utility you can run a process without maintaining an active shell session. To run a time consuming process inside a remote machine, first connect to it with SSH. Then type screen to start the screen session. You can now initiate the time-consuming process like an update or a download. When it’s underway, press Ctrl+A and D to detach from the screensession but leave the process running. You can then terminate the SSH process. Later on when you reconnect to the SSH session, you can check on the status of the update or download by restoring the screen session with screen -r . Use…

Adiós Administeria Time for a little bit of a change here at Linux Format: this is my last Administeria column. It’s a good idea to keep things evolving and I look forward to seeing what the great editorial team here at LXF come up with next. I thought I’d use this last 300 word section (which has always been the most difficult bit to write) to briefly mention the kinds of things I’m going to be looking at for the next year or so. They’re a mixture of skills that hopefully keep me vaguely employable— and others that I just find interesting. It really is a disadvantage in the job market now not to have any skills when it comes to the big players in the cloud computing arena. The…

It’s a fairly common requirement for applications to be horizontally scalable these days. For lightweight microservice-based infrastructures it’s an assumption that this will be possible. DC/OS handles this in a couple of different ways, with Marathon being responsible for handling the actual ramping up of capacity. The DC/OS tutorial provides an example python script (https://dcos.io/docs/1.8/usage/tutorials/autoscaling/cpu-memory) which monitors the amount of CPU and memory utilisation by a Marathon service. Based on pre-supplied metrics, this script will increase the number of app instances up to a ceiling when it calculates that the conditions have been met. A bit more sophisticated is an advanced feature of Marathon-LB that scales up based on the number of requests an application is seeing over a defined time period. The autoscale script polls the HAProxy stats endpoint…

Our expert Sean D. Conway had formal training in electronics and spent half a career in aviation, so, if anything, he really knows how to implement a GPS receiver on a Raspberry Pi. This tutorial will configure a Raspberry Pi as a web server to set up a content management system (CMS) using the popular WordPress platform. Before starting the configuration, we’ll cover what makes a CMS and follow up with how to install and configure a WordPress server and have it running and accessible from a browser. For this tutorial, you’ll need a Raspberry Pi for booting into Raspbian. You’ll also need some experience using the terminal and be comfortable using a text editor to work with files. Drupal, WordPress and Joomla are just three examples of free open…

1 Reboot your server Kick off a reboot of the server, by now you must remember the shutdown command for a restart. When the server returns, open a web browser to access the user front-end of the CMS system by entering the URL http://webpi. The WordPress platform is designed to provide step-by-step assistance in completing the configuration. We are in the home stretch now, select the ‘Let’s Go’ radio button and proceed. 2 Generate your config Fill in the question fields with the configuration data used for setting up the MySQL database. If you don’t recall them the details are in the screenshot (above). After completing the fields, select the ‘Submit’ button. Using the details provided, WordPress generates the contents for the configuration file /home/pi/www/wp-config.php . It wouldn’t be able…

The main reason why some people avoid using public shares is the matter of trust. But in most other regards, public shares are more convenient than peer-to-peer communications. Luckily, you can combine the power of both by using EncFSthe encrypted filesystem. KEncFS is an easy-to-use graphical front-end for the filesystem. Launch it and press the ‘Add’ button, give a name for a new entry, set the mount point (a destination directory) and then in the ‘Encrypted directory’ field select the directory that will show encrypted files. Finally, set the access password and enjoy the on-the-fly encryption. Using this technique, you can tell KEncFS to use ~/Public or ~/Dropbox, or whatever the path to your shared files is, as the ‘Encrypted directory’. As a consequence, if your shared files are leaked,…

Another minimalist window manager is Awesome, which aims to be fast and easily configurable. When we tried it on our system, it was faster to start than we could react. Awesome follows a similar pattern as i3 using the $mod+key scheme to map different key combinations to actions. One major difference is that Awesomecomes with a drop-down menu which lists your applications. The list is held in a standard configuration file pointed to from the rc.lua file. Using $mod+P will also show a bar at the top of the screen that lists program categories in a tree form. Use the arrow keys to navigate the tree until you find your program; this feature also enables you to type the name of the application and see matching results dynamically. You can…

For this tutorial, we used a radio link to connect two micro:bits, which enabled strings of data to be sent between devices. This used the default radio settings for ease of use. But what if we wanted to create multiple robots for battle in an arena? This is where channels come into play. The radio class has many different configuration options available to the user, but the most basic is channel. To change the channel of the radio we must use: So now we can change the channel from 0 to 100. This must be done for every micro:bit that you wish to have on a certain channel. If you would like your radio signal to go further, then you’ll need to increase the power of the transmission. This is…

After learning about Nginx, you might ask whether Apache is still a good choice. Well, before Nginx, Apache was the most popular web server, which means that it’s still good. Apache is a process-based web server, which means that each simultaneous connection requires a separate thread. The main reason for having a separate execution for each request is that this is the only way to avoid blocking when using synchronous I/O. As you may appreciate, the way Apache works is simple to implement and can easily serve websites without lots of traffic provided that your Linux machine has the right amount of memory and CPU power. Apache uses .htaccess files and Nginx doesn’t support .htaccess files, so you’ll have to convert existing Apache .htaccess files into Nginx rules which looks…

This tutorial has various instances where DOM is manipulated with JQuery. To access a DOM element with JQuery, the selector is often the first part of the process. For example, let’s look at $(’.myName').show(). The selected element is actually any element with the myName class. In some cases, that could be exactly what you want to select. Now, to reinforce this, look at $('img.specialImage'). The item selected here is any image on the page with the class called ‘specialImage’. Thus, the HTML for this item would look like <img class="specialImage" src="myImage” />. As you can see, the second example was a little more specific. Although that may seem as specific as you might need, you may end up with a situation when you must be much more specific because you…

Unix applies a concept of standard streams of data, which means that each program automatically gets access to three data streams: input, output and error. Each standard stream has a file descriptor associated with, 0, 1 and 2 respectively. A file descriptor is just a number used for referring to an open file. The following command shows how to use a single file as an input to another file: Note: This method doesn’t work with multiple files. But with this approach you can take advantage of standard input, output and error as well as how to redirect standard error to standard output and ignore the standard error output entirely with a redirection.…

Linux Format is proud to produce the biggest and best magazine that we can. A rough word count of LXF217 showed it had 65,010 words. That’s a few thousand more than Animal Farm and Kafka’s The Metamorphosis combined, but with way more Linux, coding and free software (but hopefully less bugs). That’s as much as the competition, and as for the best, well… that’s a subjective claim, but we do sell way more copies than any other Linux mag in the UK. As we like giving things to our readers, each issue the Star Question will win a copy or two of our amazing Guru Guides or Made Simple books – discover the full range at: http://bit.ly/LXFspecials. For a chance to win, email a question to lxf.answers@futurenet.com, or post it…

★ Kali conundrum Q I am having problems trying to get a Kali Linux and Mac OS X dual boot on my friend’s MacBook as when I installed Linux there was no Wi-Fi chip found. I did some research and found it was a common problem. I managed to get a USB to Ethernet working with the internet, but when I use apt-get install Thenameofthedrive it says 'package not found' and the same error occurs when I try installing different applications that had worked for me previously. A bit more research later I found that adding some repositories might help but using apt-add-repositorie/s , it says 'command not found'. Paul Fawbert, 12 and a junior pen tester A The wireless network adaptor in the MacBook Pro is not supported by…

System tools Essentials Checkinstall Install tarballs with your package manager. Coreutils The basic utilities that should exist on every operating system. HardInfo A system benchmarking tool. Kernel Source code for the latest stable kernel release, should you need it. Memtest86+ Check for faulty memory. Plop A simple manager for booting OSes, from CD, DVD and USB. RawWrite Create boot floppy disks under MS-DOS in Windows. Smart Boot Manager An OS-agnostic manager with an easy-to-use interface. WvDial Connect with a dial-up modem. Reading matter Bookshelf Advanced Bash-Scripting Guide Go further with shell scripting. Bash Guide for Beginners Get to grips with Bash scripting. Bourne Shell Scripting Guide Get started with shell scripting. The Cathedral and the Bazaar Eric S Raymond’s classic text explaining the advantages of open development. The Debian Administrator’s…

It’s one of those issues where we’ve had to sneak the main feature past management to get it into the magazine. But using the terminal is so core to Linux day-to-day life we were way overdue a decent look at the subject. Over the last year of Linux Format we’ve been slowly pecking away at the terminal with a regular tutorial section, but like the clichéd guided horse there’s no reason that someone might try it unless they’re forced to! So we’re forcing you by dedicating our cover feature to mastering the Linux terminal. We’ve been inspired by the Linux Foundation LFS101 course you can try at edx.org for free. If you’re at all interested in boosting your Linux skills we’d encourage to take a look, as it’ll take you…

While 64-bit processors are becoming ever more popular, there’s still a number of us who use 32-bit hardware and while there will always be distros available that support older and legacy hardware, there have also been some recent announcements that make finding a distro to run on 32-bit software much more difficult. For example, it has been announced that Tails 3.0 will require a 64-bit x86-64 processor, with support for 32-bit ending on June 13, 2017. As the Tails project mentions in its announcement of the news, only 4% of Tails users use a 32-bit computer. While it’s not good news for that small minority, the team behind Tails say that the move to 64-bit only will benefit its users, thanks to improved security features and greater compatibility between the…

DEFT 2017.1 ZERO DEFT (Digital Evidence & Forensic Toolkit), a customised version of the Ubuntu live CD, is back after a hiatus of two years with version 2017.1, also known as ‘Zero’. Specially designed as a lightweight tool for performing forensic acquisition of digital evidence, the new version supports NVMExpress memory (found in the 2015 MacBook), eMMC and UEFI. It can be run entirely in RAM (as long as you have over 400MB) and it is based on Lubuntu 14.04.02 LTS. DEFT Zero will be updated and developed alongside the full version of DEFT. You can find out more and download the live CD at www.deftlinux.net/2017/02/13/deftzero-2017-1-ready-for-download. CRUX 3.3 Crux is a lightweight distro that doesn’t rely on systemd and is aimed squarely at experienced Linux users. A new version of…

Broken PDFs I have subscribed to LXF for several years and often read the PDF version when looking for a specific past item. I have noticed that issues 213 and 214 appear with no text content—I assume the PDF’s are broken… Graham Andrews Jonni says: I’ve just checked those PDFs and they appear to be OK. They work in Firefox’s built-in viewer on my Linux install and they work in macOS’s preview on my Mac. Which PDF viewer are you using? We often get people writing in with difficulties when using old versions of Evince (Gnome’s PDF viewer), but I’m assured it works in newer versions. In fact, I’ve just tested it in the latest one and it’s fine there too. So I’m pretty sure this is a problem on…

Helpful documentation and active support avenues play an important role in the uptake of any software. This is especially true for privacy-enhancing distros that can often be frustrating and involve a learning curve even for people familiar with Linux. Tails offers in-depth end-user documentation in multiple languages with general information, first steps, commonly asked questions and detailed explanations to make you aware of common issues related to privacy and the importance of encryption. There’s even an XMPP chat room, a support mailing list and a form to request features. Whonix won’t let you down either with its wiki containing detailed documentation. The distro also offers several support options and has a very active forum. To assist new users, TENS’ s website contains several thorough FAQs as well as a Quick…

“while the graphical tools have made the CLI optional, most only expose a small subset.” Despite the leaps and bounds that Linux desktops environments have made over the years, there are still moments when accomplishing a task requires you to fire up a terminal. Since none of the other mainstream operating systems rely on the Command Line Interface (CLI) in the same way as Linux, it’s often quite intimidating for new users. Fear of the CLI is simply not acceptable to anyone at LXF towers. The command line is a powerful portal to some amazing tools that makes it possible to accomplish tasks much more quickly than you could with graphical tools. Whether you want to install software, configure your network or tweak other system settings, you can do it…

Links enable you to create an association between two files or directories. This is useful for maintaining multiple versions of a file or directory without the overhead of additional disk space for storing multiple copies. Links can either be hard or symbolic and we can use ln to create a link between two files. By default, the ln command will create a hard link between these files. Hard links create an identical copy of the linked file on disk that gets updated automatically as the source file gets updated. While the content of the two files are linked, if the source file gets deleted, the target file will continue to exist as an independent file. An important thing to note about hard links is that they only work on the…

One of the best things about the CLI is that it lets you combine small individual commands into a complex and useful task without much effort. This is accomplished with the pipe ( | ) operator. It is used to sending the output of one command as the input for another. For example, ls -a | grep _ uses the ls and grep commands to list all files that contain the underscore character. In the example, we’ve used the | operator to sort through the verbose output of the ps command to find the processes that are associated with a particular application, such as LibreOffice. You can do some amazing things with the | operator. We mentioned earlier that Bash maintains a history of commands. You can print the entire…

You can make a home server out of any old bits and pieces you have lying around, but that doesn’t mean you should. At least not as regards old disk drives and power supplies—these things have a habit of failing as soon as you start relying on them, and we would rather our server be reliable. In terms of processing power, a dual-core chip from the last decade will suffice for most things you might want your server to do: host files, print and run web services. However, if you plan to use it for streaming movies around the house (e.g. with Emby), something more powerful (like a recent Core i5) will be better—on the fly video transcoding is quite an onerous chore for older CPUs. Memory (at least DDR3…

Mesos-DNS provides service discovery within a DC/OS cluster. It automatically allows applications and services to find each other via DNS. When an application is launched by Marathon, it gets assigned a name using the naming pattern task.scheduler.mesos. In all of my cases here, that means task.marathon. mesos. So, for example, when I want to find out the IP address of my MongoDB service, I can just issue the command And get a result like the following (which I’ve edited for brevity). I can go on a little further though—I can use the command (below) which will give me the information on which host the MongoDB service is running at the current time, but to find the port I need to connect to, I have to look at the service locator…

Our expert Les Pounder Les is a hacker and maker who loves tinkering with Raspberry Pi, Arduino and micro:bit. He trains teachers with the Raspberry Pi Foundation and writes up his adventures at http://bigl.es You will need: Raspberry Pi 2 or 3 Model B Raspbian Pixel 1x Infrared obstacle sensor 3x Jumper wires (to connect sensor to GPIO) Speaker Power supply Wi-Fi connection Optional box to store the project All of the code for this project and a detailed diagram can be found at https://github.com/lesp/LXF222-Butler/archive/master.zip. Personal assistants vary in their design and scope but what are the basics? Well, it should be easy to use and provide instant access to information. Fortunately, creating one can be quite simple. We’re going to create a project where waving your hand in front…

Before loading the software components it is good practice to ensure that the distro is updated, so it has all the newest versions of all packages currently installed on the system from the source repo: The upgrade command is used to install the newest versions of all packages that are currently installed on the Pi. An update command is performed first so that apt-get knows if new versions of packages are available for upgrade. Restarting an OS after major changes will help in the long run. It make troubleshooting problems easier. Performing a number of tasks on an OS before rebooting creates the difficultly of trying to determine what change may have caused the error.…

Our expert Alexander Tolstoy has a torrent server running on a constantly charging phone somewhere in his house. He’s lost it but connects via SSH, so it’s not really a problem. Transferring large amounts of data between remote computers can still be challenging for many Linux users. Sometimes you just don’t want to write it on an external hard drive or upload to a cloud-based service. Both ways take much time and effort while not being very safe. In this tutorial, we’ll examine methods for sharing files using the peer-to-peer (P2P), which is a top-notch technology for interchanging data. The big entertainment corporations may not like the technology due to possible copyright laws infringement, and we certainly don’t endorse sharing files that you don’t have a right to, and start…

Our expert Mats Tage Axelsson has spent decadesmaking his computers run Linux. His first was a ThinkPad laptop from IBM when the company was still making them. When it comes to the graphical user interface, the major Linux distributions (distros) will provide you with a compositing Window Manager (WM). In this tutorial, we’ll examine the alternatives to help you make a bold choice and perhaps try something different such as a tiling WM. First, we’ll start with the types of window managers that exist. After that, we discuss some popular, and more obscure alternatives, and examine the impact they have on both your machine and your productivity. Compositing is the most common type of window manager, but there are also stacking and tiling window managers. The stacking and compositing versions…

FVWMstarted a long time ago in a Department of Defence office, when Robert Nation started hacking the twm window manager. Of course, twm also has a history but that’s another story. Nation’s main goal was to reduce memory usage while adding support for virtual desktops. In June 1993 he bundled it with rxvt, a project he’d been working on, which was already successful (and still is). As development continued and maintainers changed, the meaning of the F in the title, which had originally meant ‘Feeble’, became lost. When the original announcement was retrieved from newsgroups, the developers decided to leave the F’s meaning mysterious. FVWMhas since been used to create new window managers (some that we’ve mentioned in this tutorial). Xfce is one notable one which has become the default…

In this tutorial, we used a motor driver board to interface our micro:bit with two motors—but why did we need that controller? The controller is simply there to buffer the micro:bit as motors require a considerable amount of current in order for them to start moving. This is current that the micro:bit is unable to provide without potentially damaging the unit. We used a Kitronik motor driver board, but at its heart is a DRV8833 motor controller that uses an H bridge or ‘flip flop’ circuit to control the direction of the current. Remember in the tutorial we changed the polarity of the motors to change direction? Well, that’s the H bridge circuit in operation. But do you need to buy the Kitronik kit? You can make your own by…

Nginx works differently to Apache mainly because of the way it processes requests. A side effect of this is that Nginx processes requests faster using fewer system resources. Nginx uses asynchronous sockets that allow it to handle more requests per process while not having to spawn too many children (worker) processes. As a result, the memory consumption of Nginx is very low when serving static pages. The configuration files of Nginx are simpler to read, use and modify than the config files of Apache. The only reason Nginx uses multiple processes, is to make full use of multi-core, multi-CPU and hyperthreading systems that are currently being used. User requests are served by the worker processes that Nginx server starts. The number of worker processes the Nginx creates is defined in…

With AngularJS, especially for newcomers, many of your usual repeat tasks can become more complicated to implement. Thus, if your files for your application are PHP files, you have options to switch in and out of an Angular application. To make this process simple, you can do a few things. With our example, let’s say you have a website and want to run Captcha2. The first step you can take is to change a link in your main menu, footer and wherever else from something like <a href="#/contact"> to the actual PHP page. This means the new link will look like <a target="_self” href="contact-us.php">. The target is required. This a new workaround for the Angular route. But since the index.php page is an Angular app, you need to ‘deangularise’ it…

When you execute a Linux command or a script you usually provide some text after the name of the program, which are called command line arguments, can be accessed in every programming language and Python 3 is no exception. Traditionally, command line arguments on a UNIX system are stored using an array or a similar data structure—the first element of the array, which has an index number of 0, is usually the name of the program itself! You can process command line arguments in Python 3 as follows: If you name the previous Python code as aStrangeScriptName.py, make it executable and run it, you will get the next output: As you can see, the first print() command displays all of the arguments, whereas the for loop goes on to process…

Nothing is more infuriating than random crashes of a computer. If a crash is reproducible, you have somewhere to start looking, but if it happens at any time and using any software, where do you look? If it happens regardless of the software you are using, it may be a hardware problem. If you have a spare PSU, try swapping that. If it’s a laptop, the battery may be on the way out. If the computer doesn’t run reliably on battery power alone, look for a replacement battery. The other common culprit is faulty memory. Not all of it, just a few bytes. Testing memory on a running system is unreliable as you can't test anything the system needs, so use Memtest86+. This is a bootable system that uses minimal…

We receive several questions each month that we are unable to answer, because they give insufficient detail about the problem. In order to give the best answers to your questions, we need to know as much as possible. If you get an error message, please tell us the exact message and precisely what you did to invoke it. If you have a hardware problem, let us know about the hardware. If Linux is already running, use the Hardinfo program (https://github.com/lpereira/hardinfo) that gives a full report on your hardware and system as an HTML file you can send us. Alternatively, the output from lshw is just as useful (http://ezix.org/project/wiki/HardwareLiSter). One or both of these should be in your distro’s repositories. If you are unwilling, or unable, to install these, run the…

At first glance, Linux Mint and Scientific Linux would not appear to have much in common, but that’s not the case. Both are based on commercially supported distros and both are community developments. These are important points. We have companies such as Canonical and Red Hat taking free software and turning it into a commercial product, but in turn they have, and choose, to give their changes back to the free software ecosystem. Then one of the great advantages of the free software and open source environments comes into play: the idea of community. With our communities there’s no divide between a software vendor and its user, anyone can use the software and anyone can submit changes to it; the lines between user and developer become blurred allowing people to…

Building better IoT Pi Zero W Pop on your maker hat, it’s time to combine Linux, Python and the new Pi to create secure IoT devices! What happened to Blu-ray? The digital download revolution is the obvious answer, but let’s explore playing Blu-ray discs on Linux. Android Studio Get a leg up with Android app development building a base Android development environment. Open source CAD With the Maker revolution here everyone needs decent CAD software, we explore what FOSS has to offer. Contents of future issues subject to change – we might be too busy innocently joining Russian botnets.…

Kodi is a very popular piece of open source media playing software, and while it’s easy and free to download and install Kodi on a large number of devices, including the Raspberry Pi, there is also a growing market for set top boxes that are sold with Kodi pre-installed. The problem is, there are many third party add-ons that aren’t endorsed by the Kodi team, and are primarily used by people to stream and download subscription and pirated media for free. Boxes with Kodi and these add-ons pre-installed are being subject to a crackdown, and a shopkeeper from Middlesbrough is pleading not guilty in a landmark case that could determine the legality of selling ‘fully loaded’ Kodi boxes in the UK. The trial begins in May. http://bit.ly/LXF222kodi Mesa 17, the…

“Mesa 17.0, the latest release of the open source 3D graphics library was made available this February 2017. With nearly 2,500 commits from over 120 developers, Mesa 17.0 is without a doubt a hefty upgrade over the previous development release. It also brings a new versioning scheme reflecting the release year For the first time an open source driver meets all the latest conformance test suites for OpenGL, OpenGL ES and now Vulkan, a feat achieved through significant investments in Mesa over the years. Key features of this latest release include OpenGL 4.5 support for Intel Haswell, Open GL 4.3 support for NVIDIA Maxwell, support for multiple devices with the Radeon Vulkan driver (RADV), and Float64 support as well as tessellation shader support with the Intel Vulkan driver (ANV). The…

Recently, I was reading your Raspberry Pi section with my daughter (age 9, wants to be a programmer when she grows up), and she noticed an interesting thing about your magazine that we thought we’d share with you. Throughout the whole magazine women/girls are represented just seven times – two pictures of Rose from Dr Who, the woman in the cartoon, a woman in an advert, two mentions of (nameless) wives and one of a mother. My apologies if we missed anything or if any of the names that are unclear (e.g. Geordiejedi) are women! No contributors, as far as I can tell, are women. I realise that you want the best contributors, but it is a huge issue to young people—there is the saying, ‘if they don’t see it,…

A bitter truth of the open source development model is that projects lose steam and die. The same holds true for security and privacy-centric distros as well and there have been several worthy contenders that have either perished or continue to exist with their development in a state of suspended animation. While we don’t usually rate specialised distros according to their development state, it plays an important role while comparing the distros in this Roundup. After all it’s imperative that the distro you choose keeps pace with the ever evolving nature of threats to your online and offline privacy. If you’re wary of new projects you may want to stay clear of Subgraph, despite its amazing set of feature, since the project is in the very early phase of development.…

Each file in Linux has a set of user and group permissions, and you can use ls -l to see a file’s full set of permissions and attributes. The output begins with the permission flags like this drwxr-xr-x that has four components: The first character indicates whether the corresponding item is a directory or a file with a directory marked with a d character and a regular file marked with a hyphen ( - ). The next nine characters are broken up into sets of three characters each, which indicate permissions for the user, group and everyone else respectively. The r denotes read permission, w is for write permissions and x points to execute permissions. The first entry in the example reads rwxrw-r-- , which means the user has read,…

Many popular distros have traditionally used SysVinitfor starting and controlling services. But this has now been replaced, in a somewhat controversial fashion for some users, by a new system and services manager called Systemd. The Systemdservice manager uses the systemctl command to control the services. If you enter the systemctl command into a terminal window it will to list the status of everything that is controlled by Systemd. If you follow this up with systemctl list-units -t service command, which will list the active services. You can check the status of any individual service with the systemctl status command, such as systemctl status sshd. service . Similarly, you can change the state of the service by replacing status with start , restart and stop . For example, sudo systemctl start…

Cory Doctorow is an award winning author, thinker and speaker. He has written many things, young adult novels, science fiction and non-fiction commentaries on the exigencies of modern society. They are all fantastic, available in DRM-free formats and released under Creative Commons licensing. He is Honorary Steward for the Shuttleworth Fellowship program and co-editor of the Boing Boing blog. He is a digital rights activist and serves as Special Advisor to the EFF. Through the Apollo 1201 project, he’s part of a mission to rid the world of DRM. Linux Format: Without sounding too much like a hysterical screaming fan, I have to tell you that I am a huge fan of your work and it’s an absolute honour to be sat here with you. Cory Doctorow: Thanks man, that’s…

Logging into SSH using a key involves first generating a private key and a public key. It’s your responsibility to keep the private key as secret as can be. It’s convenient to have a copy on every machine you log into the server from, but also insecure—if one of those machines was stolen it represents a vector by which our server could be compromised. Ideally you should keep the private key on a USB stick and not lose it. The public key can be just that, and a copy of it is stored on the server to verify the private key via mathematical voodoo. To generate a keypair (ideally on a machine that you’ll access the server from, rather than the server itself) run the command ssh-keygen . Accept the…

“An abundance of noise reduction tools that cover lots of areas.” Photo editor RawTherapee Version: 5.0 Web: http://rawtherapee.com Although the overwhelming majority of mortals shoot photos using their smartphones these days – and largely selfies – there are still a large community of people who care about every pixel and demand the highest quality for their digital images. To join the club you need to ignore the lossy JPEG format in favour of RAW, the format of pure data from a DSLR camera sensor. RawTherapeeis a well-established tool for digital photography in Linux, especially for managing RAW files. The application’s general aim is to make the best out of your camera’s photos with more accurate colours, less noise and smoother skin tones, etc. Gaining skills in restoring and enhancing RAW…

Adding extra functionality to our project, we used a popular open data provider to provide precise weather data for our assistant. The Open Weather Map website, http://openweathermap.org, offers a free (Application Programming Interface) API for use with many different languages. For our project we used Python 3 and installed the pyowm library for a pythonic method of using the API. In order to use the service you will need to sign up as a registered user. This is a free service. Once signed in go to API Keys and create a new key and remember to give it a name. You can have multiple keys at any one time, but most users just need the one. Your API key will need to inserted into the Python code for this project,…

In the early days of website development, the emphasis was on designing the web pages around the content. The site content was hard coded in HTML. Supporting the server required comprehensive webmaster skills. The development of Content Management Systems (CMSes) changed website design by separating the content from the page code. In a CMS, the web pages are fed content instead of being embedded in the code, which enables the content to be managed with minimal skills. An effective method for understanding a CMS is to divide it into two subsystems: One is content management. The components used in the management subsystem enable creating, organising, modifying and deleting website content. The other subsystem is content gathering that publishes content to the web and manages workflow.…

There are various BitTorrent clients that can be used in command-line mode. This approach can be very beneficial if you want to set up a dedicated machine for file sharing and then control it remotely via SSH or otherwise. Linux has plenty of console-based torrent software to offer, including Ctorrent, Rtorrent and Transmission. Let’s see how the latter works. Transmission is known as one of the most popular graphical BitTorrent clients, but it often comes with packages such as transmission-cli and transmission-daemon designed for remote usage. The great power feature of the command-line version of Transmissionis that you can daemonise it, i.e. you don’t need to stay connected to the host all the time the torrents are downloading. You can set it up once and have the daemon run in…

TinyWMonly contains 50 lines of C-code, the code depends on Xlib and calls very few functions, creating a binary smaller than most. The code is on http://incise.org/tinywm.html with one version with annotations and one without, the code is also on GitHub. The description is very thorough, detailing possible pitfalls when programming for X. Cases covered are resizing to extreme values; how to handle lag of different kinds and how to handle key bindings. Written by Nick Welch, the functionality is limited to four basic window functions: 1 Move Windows interactively, using the Alt+Button1, the left mouse button. 2 Resize windows interactively, using the Alt+Button3, the right mouse button. 3 Raise windows, using Alt+F1. 4 Focus windows with the mouse pointer. The list, as you can see, is very short which…

Our expert Les Pounder is a (gentlemen) hacker/maker who loves tinkering with Raspberry Pi, Arduino and micro:bit. He trains teachers for the Raspberry Pi Foundation and writes up his adventures at http://bigl.es. We introduced MicroPython, in a previous tutorial [see Tutorials, p88, LXF221], by learning how to create our own Iron Man-inspired light glove that reacted to input, in the form of coordinate data, taken from an accelerometer built into the micro:bit. For this tutorial, we shall build something even better! One of the most popular projects for beginner hardware hackers is creating a robot. We’ve seen many different versions, typically using various models of the Raspberry Pi as the brains of the robot attached to many different motor control boards and robot chassis. But since the release of the…

Our expert Mihalis Tsoukalos is a DBA, mathematician, programmer and Unix admin. He enjoys writing articles and learning about programming languages. You can reach him at@mactsouk. This tutorial will cover the Nginx web server and its use by presenting valuable information, tips, error messages, log entries and example configuration files for Drupal and WordPress sites. After installing Nginx on your Linux machine, using your preferred distro, you can find out its version by executing the following command: On Ubuntu and Debian machines, the default directory for the Nginx configuration files is /etc/nginx where nginx.conf, the main config file is located. Although you can define new websites inside nginx.conf, it’s better practice to define new sites inside the /etc/nginx/sites-enabled directory, because the default nginx.conf file automatically reads everything that’s inside it…

Our expert Kent Elchuk is a freelance full stack and web developer for a college in Vancouver, Canada. He enjoys both front- and back-end development. This tutorial is an extension of a JQuery and AngularJS article we published previously [see Tutorials, p88, LXF218]. If you’ve read that tutorial or have the coding sample that will help. If not, you can still follow along as this tutorial is about extending AngularJS’s appearance and functionality. We’ll be covering how to add a new theme to a one-page application; using AngularJS to create image galleries; the everyday features used in basic web development and changing its appearance with Bootstrap, CSS and JQuery. The main file that’s run is called index.php. As a refresher, the specialised content that runs for each page, such as…

Our expert Mihalis Tsoukalos (@mactsouk) has an M.Sc. in IT from UCL and a B.Sc. in Mathematics, which makes him a DB-admining, software-coding, Unix-using, mathematical machine. You can reach him at www.mtsoukalos.eu. The subject of this tutorial is programming the famous wccommand line utility in Python 3. This utility is a relatively simple tool with only three main command line switches, which we’ll also implement here. In other words, when you implement such a famous utility, it’s easy to decide what you want to support, so you don’t have to think a lot about the features your program will have. One of the oldest Unix command-line utilities, wc, which is short for word count, enables you to quickly find out information about a text file. The wcutility does various things…

This month we answer questions on: 1 Sending email automatically 2 Using the mKiosk extension for a Firefox info system 3 Opening VNC to the internet 4 Picking a distro 5 EFI bootloader ★ Networking Linux Kali 1 Automated email Q Before I retired I worked in a Microsoft environment. Using VBA, I could control Outlook to send emails as and when required at the touch of a button. I now wish to replicate that under Ubuntu 16.04—can this be achieved using Thunderbird or some other email service and maybe Gambas or C# on Mono? Mike Higgins A Sending emails from the command line with Linux is easy and doesn’t need a specific language or mailer. The easiest way is with the mailprogram, a command line mailer. All you need…

We often give a solution as commands to type in a terminal. While it is usually possible to do the same with a distro’s graphical tools, the differences between these mean that such solutions are very specific. The terminal commands are more flexible and, most importantly, can be used with all distributions. System configuration commands often have to be run as the superuser, often called root. There are two main ways of doing this depending on your distro. Many, especially Ubuntu and its derivatives, prefix the command with sudo , which asks for the user password and sets up root privileges for the duration of the command only. Other distros use su , which requires the root password and gives full root access until you type logout. If your distro…

Reset Why do computers have reset buttons? Because they come with Microsoft Windows operating systems. That joke is so old I first heard it from a Stegosaurus. Are you saying that Linux programs never crash? The Linux kernel is very stable and application crashes usually don't affect the rest of the system by much. But occasionally a rogue process will muck things up, using up all your CPU or RAM (or both) and requiring a reset. Or a kernel panic will stop the boot process dead in its tracks. So we still need the dreaded reset button, don’t we? Well, no we don’t. Linux has a little magic in the kernel, whenever you press Alt, the SysRq key and a command key, the kernel will always respond to that command,…