Linux FormatApril 2020的目錄

“ I was recently reminded of a story from my early days in IT. Six months after starting work at Digital Equipment Corporation, I was at my first job review. In those days I repaired computer terminals – just printers or VDUs that connected to a computer elsewhere in the building. Things had been going well, and I was looking forward to the meeting. We sat down, and after the small talk my manager asked me what my job was. “Fixing computer terminals,” said I. “No,” he replied sagely, “it’s fixing customers.” That was a long time ago, but his words are still true today. For those of us in customer service roles, fixing the customer remains the goal. Linux is a vast subject. You can’t be expected to fix…

“Virtual Private Networks started life as a means for remote users to safely participate in local networks, or to bridge between different company sites. Today, VPNs are used widely for all manner of other purposes as well. Maybe you value your privacy, want to work around a geographic content filter, or even just want to login to your full home network seamlessly from afar. Whatever the reason, VPNs are very useful, and yet they have often been fairly nightmarish to set up, configure and operate. The proprietary ones were bad enough, and things certainly improved when many shifted to OpenVPN, but even OpenVPN is cumbersome and complex, with many moving parts to get right. It is, then, quite exciting to see the progress being made to Wireguard, a new VPN…

Q The sound of silence I have installed the latest version of Linux Mint on my HP Spectre laptop. I keep it updated with software updates. My only issue is that when I plug in the wired headphone in the jack, the sound does not work. Can you please help me identify the problem and a possible fix? Sajal Sachdev A When you say the sound does not work, do you mean it stops altogether or it continues to play through the speakers? If it continues to play through the speakers, ignoring the connected headphones, check your mixer settings. As Linux Mint uses PulseAudio, try pavucontrol I find this more useful than most desktop mixers for viewing and controlling audio outputs. Your system should detect your headphones being plugged…

These days plotting in Linux usually starts with an internet search for ‘best plotting OSS apps’, this predictably returns a bunch of decent reviews. They are good, but we have decided to shift the focus towards beginner-friendly applications that provide an easy-to-use graphical interface. With this in mind, we’re not including such respected packages as Gnuplot and Ggplot2 in this Roundup. Instead, we’re putting powerful and mature WYSIWYG suites (LibreOffice and Veusz) against Jade, the promising project that rivals MS Visio, as well as the classic diagramming app that’s been around for ages (Dia), and also LabPlot – the very decent tool for data analysis and plotting. The term ‘plotting’ is wide enough to be handled in many different ways, but in this Roundup we’ll mainly look at ways of…

We’ve covered the most advanced plotting applications that provide a user-friendly GUI to its users. However, there are other plotting apps that are often recommended for plotting task, but have a different way of being used. Have a look at Gnuplot, a scriptable plotting tool that can generate stunning 2D and 3D images. The main benefit of Gnuplot is that you can integrate it with your Perl, Python or Ruby scripts, use it for batch processing, or in interactive mode. Another scientific plotting option is Matplotlib, a Python library that should be used via scripting. If you are familiar with the Python syntax, you can produce high-quality 2D and 3D plots and charts ready to be published as a hard copy. That’s not everything – some people prefer LaTeX as…

It’s easy to confuse virtualisation and emulation. Both are a piece of software masquerading as a machine, and both have been around for a long time. In one sense virtualisation is just a special form of emulation. On Linux, we can emulate lots of hardware; for example, a Raspberry Pi with QEMU, an Amiga with UAE, or a Sega Megadrive with BlastEm. We can also emulate software, using DOSBox or Wine (we know, Wine isn’t an emulator – arrest us) for example. Emulation recreates everything in software, translating or rearranging foreign code into something the host can understand. Virtualisation differs in that the guest code runs directly on the host, which means it’s faster (although sometimes other hardware still has to be emulated which makes it slower again), but also…

The CPU vulnerability can of worms that was opened in January 2018 with Spectre and Meltdown shows no sign of ceasing to spew its vulnerability worms everywhere, with new speculative execution vulnerabilities (CacheOut, Zombieload v2, L1DES and VRS) made public this year. These enable an attacker – albeit by pretty complex means – to access memory that they shouldn’t be accessing. One of the major concerns is that on a host running multiple VMs, such attacks could break the isolation, allowing one VM to read the contents of another’s memory – even memory protected by Intel’s secure enclave (SGX) tech. Cloud giants host billions of VMs on shared machines, some of which house sensitive data, so this is a grave concern. VMs and the hosts themselves need to have fixes…

FreeBSD is similar to Linux in that there’s an extended family of other systems. There’s now quite a few different choices in the BSD world. Here are a few of the most popular: FreeBSD (www.freebsd.org) was originally a server OS first (as most Unix-likes were), but now is positioned as the “jack-of-all-trades” system, if you’re willing to put in the work in, as we’ll cover. NetBSD (www.netbsd.org) is another all-purpose OS, with a focus on running on as many different devices as possible, meaning you can just as easily find it on a desktop, a server, or replacing Windows CE on an NEC MobilePro 790 circa 2004. OpenBSD (www.openbsd.org) its claim to fame is security, with all packages going through rigorous audits at the source level.TrueOS (www.trueos.org), originally called PC-BSD,…

Vulkan is an industry-wide initiative to deliver a modern, high-performance, cross-platform API to support 3D rendering and compute abilities. It was largely created through the need to replace the more complex OpenGL library with a lower-level and less CPU-demanding API, especially for mobile devices running Android – but extending to anything requiring GPGPU compute abilities and OpenCL. Before the Raspberry Pi 4, Pi models were unable to directly support Vulkan as it requires hardware that supports OpenGL ES 3.1. Obviously, this didn’t stop the Pi community trying to bring Vulkan support to the Pi regardless… But with the release of the Raspberry Pi 4 and its VideoCore VI hardware that does support OpenGL ES v3.1, the possibility of Vulkan support became a reality. So it shouldn’t surprise anyone that at…

Our original tablet project relies on the official Pi 7-inch touchscreen display. Instead of being limited by this, consider alternative displays. You might prefer a 4-inch HyperPixel display, a 5-inch screen, or even the 10.1-inch Industrial Touchscreen display. Choose one that suits your needs and adapt the 3D printed chassis to suit. Plasma Mobile should run without trouble, but it is primarily a UI for phones. Detailed instructions on installing and troubleshooting Plasma Mobile can be found on hacker Tinker’s webpage (www. tinker.sh/kdeplamo-rpi) While 3D printing hardware has become increasingly affordable, plenty of people don’t yet own one. The affordable alternative to buying a 3D printer is to use a mail-order printing service. If you’re using designs from Thingiverse, there’s the option to Order This Printed and have the build…

Deleting files is a fairly straightforward process, whether you work with a graphical interface or the command line. The former, more often than not, relegates deleted files into the trash directory, giving you the option to access deleted files and even restore them if needed. But this isn’t the case with the popular rm command. Once invoked, rm immediately flushes the specified files, skipping the trash directory altogether. To recover a file deleted from the command line, you must use dedicated software such as PhotoRec, but the process is involved and cumbersome, and not the subject of this tutorial. If you wish to permanently delete files using the graphical environment, you must press the Shift+Del key combo. You’ll be prompted with an alert seeking confirmation before the selected files or…

Earlier version of GNU Radio Companion used WX GUI widgets. WX had some performance issues, especially with integrated graphic hardware. The replacement are QT GUI widgets. In the console drawing you can determine the widget support from Option Block. Before GNU Radio release 3.7, WX GUI was the default; QT GUI became the default widget support at version 3.7. Since the Initial development of GNU Radio was done with WX GUI, a number of Blocks were developed using that technology. Most if not all the WX Blocks now have QT Blocks to replace them. At the GRCON conference in 2018 it was indicated that with the 3.8 release of the software, WX GUI will be completely dropped. WXGUI and QT GUI are not compatible, meaning they can’t both operate in…

For small environments and test environments, Zabbix provides a virtual appliance image that may be used for a quick start. The physical requirements for the Zabbix server can be found on the Zabbix website at http://bit.ly/ lxf261zabbix. If you haven’t set up DNS yet, this is the push you need. Zabbix will work against IP addresses, but having DNS resolution provides a much cleaner and easier-to-use experience. Keep your data and apps separate. While we could use LVM and have all the data and operating system on one disk, this is bad practice and will complicate management. Should your disk get full, expanding it, while doable, gets a bit messy. It is just easier to separate an OS and apps. A full OS disk means an unresponsive server.…

In this tutorial we have configured Traefik using command-line switches in our Docker Compose file (the section starting command:). This is the equivalent of starting the application with a whole bunch of command options each time, and while this would be far from convenient to type out manually, Docker Compose makes the process fairly straightforward. The main advantage of doing it this way in our tutorial is that it means we can contain all the configuration elements in a single file (docker-compose.yml). If you look to pursue Traefik further and search the internet for examples, you are likely to find many that make reference to your configuration being placed in traefik.toml/traefik.yml files. The two different file extensions relate to different file formats, one of which we have already seen in…

Most advanced log management tools are made for professional system administrators so they have many options and plugins. The common ones that are in your repositories are the gnome-logs tool, the rsyslogd tool and the gnome-system-monitor. These tools are great for finding heavy processes and narrowing down what software is weighing down your desktop system. When you start your own web server, the amount of issues will quickly mount and you need something with more capabilities. Graylog is an example that can collect data. It uses a dashboard for your results and creates graphs for all your needs. This, like many other packages, has modules to adapt to more types of log files than they were originally built for. The package also comes as an open source or an enterprise…

Programmers are always taught to document their code with comments so that they, or someone else, will be able to understand it if they need to debug or modify it at a later date. Just the same is true of spreadsheets, so here are a few suggestions to make your creations more readable. No doubt you’ll give your spreadsheet a sensible filename so it’s more easily identifiable, but it doesn’t end there. If your spreadsheet contains multiple sheets, make sure you rename them to something more meaningful than the default names of Sheet 1, Sheet 2, etc. Next up, make sure you include a meaningful title in the very first cell so it acts as a heading. This might not be enough by itself, so consider adding a few lines…

You can learn more about Elasticsearch at www.elastic. co and at www. elastic.co/products/enterprise-search. You can find the documentation pages of Elasticsearch, Kibana and Logstash at www.elastic.co/ guide ELK is an acronym for Elasticsearch, Logstash and Kibana. Recently the ELK stack has been renamed Elastic stack. All three products are open source projects. Elasticsearch was developed first, and the other two followed next. In 2015, Elastic added Beats to the stack. Do not underestimate the power of a properly written docker-compose.yml configuration file because it can save you lots of time when you want to create the same environment elsewhere. Having a library of such YAML files can be a great asset and will save you from having to create an entire software infrastructure from scratch.…

THE LXF LIBRARY Advanced Bash Scripting Guide Go further with shell scripting. Bash Guide for Beginners Get to grips with the basics of Bash scripting. Bourne Shell Scripting First steps in shell scripting. The Cathedral and the Bazaar Eric S. Raymond’s classic text explains the advantages of open development. The Debian Book Essential guide for sysadmins. Dive Into Python Everything you need to know. Introduction to Linux A handy guide full of pointers for new Linux users. Linux Dictionary The A-Z of everything to do with Linux. Linux Kernel in a Nutshell An introduction to the kernel written by master hacker Greg Kroah-Hartman. The Linux System Administrator’s Guide Take control of your system. Tools Summary Overview of GNU tools. GNU Emacs Manual Six hundred pages of essential information! Producing Open…

This issue Jonni has been getting very angry at me for conflating the terms ‘emulate’ and ‘virtualise’ – and don’t even get him started on ‘containerise’. Part of the issue was that I hadn’t clocked that virtualisation only includes systems running on the same hardware platform. I think it’s an easy enough mistake to make; the x86 platform is so dominant, it’s about the only thing you are going to virtualise. That world is changing though; the idea that, for Linux Format readers, x86 is going to remain the dominant platform in your lives just isn’t true any longer. There’s a good chance that Arm plays as much of a role, be that in the Raspberry Pi, your smartphone, tablet or smart TV. With Amazon already running its own design…

Godot (https://godotengine.org) is a powerful open source game engine that is turning into a formidable set of tools (we last reported on Godot back in LXF255), and there has been another run of good news for the project. First of all, it’s been announced that the Godot Engine has been awarded an Epic MegaGrant. Given by the Epic Games studio (founded by Tim Sweeney and behind games such as the ridiculously popular Fortnite, as well as the Unreal Engine. The grant, which totals $250,000, was awarded to Godot after the team applied for it in the category of open source graphics software, with the purpose of improving graphics rendering, as well as the built-in game development language GDScript. As the Godot team explain (http://bit.ly/LXF261Epic), they are discussing how the award…

Linus Torvalds announced the first couple of release candidates for what will become Linux 5.6. This came following the closure of the merge window (the period of time during which disruptive changes are allowed) that had fallen close enough to the Christmas period last year that the number of patches was “smaller than usual”. Of course, as Linus says in his announcement, “‘slightly less’ is still just that – we still have more than 10k commits”. Which is a lot of commits. The new kernel includes a number of interesting features, among them support for the Arm E0PD extension, which provides constant time TLB handling so as to undermine certain timing based side-channel attacks on hardware with the new feature. There’s also time namespaces, the WireGuard VPN (see left), complete…

BradLUG BCB Radio, 11 Rawson Road, Bradford BD1 3SH. 7–9pm on the second Tuesday every month. http://bradlug.co.uk Cornwall Tech Jam Second Saturday of the month, alternating between Bodmin and Camborne. www.cornwalltechjam.uk Roanoke Linux Users Group Every third Thursday of the month at Roanoke South County Library. https://roalug.net Medway Makers Meet every 3-4 Weeks on a Sunday. Full details at www.eventbrite.com/o/medwaymakers-8800006845. Leeds Hackspace Open night every Tuesday 7pm-late. Open day second Saturday of the month, 11am-4pm. http://leedshackspace.org.uk rLab Reading Hackspace Unit C1, Weldale St, Reading. Open sessions Wednesday from 7pm. http://rlab.org.uk Huddersfield Raspberry Jam Meet every month at Huddersfield Library, typically the fourth Saturday of each month. Huddersfieldraspberryjam.co.uk PLUG: Provo Linux User Group Third Tuesday of every month at 7:00pm at the UVU Business Resource Center in Orem. https://plug.org Horsham Raspberry…

We’d love to try and answer any questions you send to lxf.answers@futurenet.com, no matter what the level. We’ve all been stuck before, so don’t be shy. However, we’re only human (although many suspect Jonni is a robot), so it’s important that you include as much information as you can. If something works on one distro but not another, then tell us. If you get an error message, please tell us the exact message and precisely what you did to invoke it. If you have, or suspect, a hardware problem, let us know about the hardware. Consider installing hardinfo or lshw. These programs list the hardware on your machine, so send us their output. If you’re unwilling, or unable, to install these, run the following commands in a root terminal and…

Sometimes you receive raw data that needs to be processed before plotting. In Veusz, look under the Data > Operations menu and find lots of options for manipulating data sets. Joining, merging, finding the average, filtering and many more are available. Some plots in Veusz are analytical by nature, such as the covariance (say what now? – Ed) plot or the vectorfield plot. LabPlot seems to be even stronger in terms of analytics. It can perform linear and non-linear regression analysis, numerical differentiation and integration, data smoothing, Fourier filtering and more (see the Analysis menu). Given that LabPlot supports integration with different open-source computer algebra systems (CAS) like Maxima, Octave etc., it is simply a heaven for scientists who work with big amounts of data! A comparable set of data…

One of the easiest ways to fire up your first virtual machine is with Oracle’s VirtualBox. This is free (GPL2-licensed) software available for Windows, macOS and Linux. Mac and Windows users should download it from https://virtualbox.org, and Linux users should install it with: It looks and works the same for all platforms, so no matter what your OS (or which OS you want to virtualise), you can make use of our handy six-step guide opposite. If you’re stuck for a distro to try, why not copy the Solus or OpenMandriva ISO files off the LXFDVD? If you were to tell VirtualBox to use it straight from the disc things would be awfully slow. If you find yourself stuck in fullscreen mode, use Right Ctrl+F to return to windowed mode. If…

We mentioned that QEMU’s job in the QEMU/KVM duality is to emulate hardware, and we’ve alluded to the fact that this is a relatively slow process. So rather than emulate such things, it makes sense to tell the virtualised OS that it is thus, and that the hardware it can see is not real. In this way we modify the OS (or in this case its device drivers) and have the hypervisor present abstract paravirtualised hardware, which both sides conspire to handle nicely. The framework KVM uses for this sourcery is called virtio, and its drivers enable paravirtualisation of block devices, video cards, network devices and the interestingly named balloon device (used for memory management). The virtio drivers need to be installed on the guest, but have been part of…

Erik Nordmark is one of the co-founders and the chief architect at Zededa, pioneers in edge virtualisation and creators of Project EVE – the Edge Virtualization Engine. For anyone that doesn’t buy into new computing paradigms, Erik claims “the edge is already here, it’s just not connected yet.” And he would know. He also sits on the technical advisory committee of the Linux Foundation’s LF Edge umbrella organisation (https://lfedge.org), which brings together seven (and counting) projects, including Project EVE (and EdgeX Foundries, which we heard about in LXF257). LF Edge has the lofty goal of establishing an open, interoperable framework for edge computing. Erik was brave enough to join Jonni Bidwell among the clouds on the roof of the Lyon convention centre – skirting dangerously close to all kinds of…

While it may not be compatible with other BSDs, FreeBSD does come with a feature that enables you to run Linux software on it. The Linux Binary Compatibility layer allows you to install both 32 and 64-bit Linux applications, although it appears the support for i386-based software is fading. To add Linux compatibility, first add the Linux module for the FreeBSD kernel (while logged in as root): Then install the package (or build the port) for the emulation layer: Add the following to /etc/rc.conf/ to make sure Linux compatibility is loaded at start-up. Your FreeBSD system is now set up to run Linux programs. Some other considerations you may need to take into account include: Does the program require any shared libraries? If so, you’ll need to track them down…

For the past few weeks I have been immersing myself in the 1980s – specifically, BASIC programming on a Z80 board called the RC2014 Micro. It got me thinking about those golden days. I learned to code using BASIC, and I could even do some rudimentary GPIO and electronics work thanks to a series of books from Usborne Publishing, which are now free to download as PDFs. BASIC is a great language, and it struck me that because I can already code in a few other languages, I picked up BASIC quickly and made a few projects using the language. Learning to code is not just about learning a language – it is about how logic works. How a loop can iterate, how to declare a variable, set the variable…

The Sense HAT is a scientific platform created for use in schools and in space! Two Raspberry Pis are currently on the International Space Station as part of a scheme with the European Space Agency, where children can write code and potentially have it run on these high-flying Pis. The competition is called Astro Pi, and the code written by the schools can be silly or serious. Is there a north in space? Well using the Sense HAT you can find out, just as one school did. The Sense HAT has sensors to measure temperature, humidity, pressure, magnetic forces, orientation or acceleration, and it has a lovely 8x8 grid of multicolour LEDs on which we can scroll text and display pixelated images. The joystick provides basic input – handy when…

If you have accidentally lost precious data because of hasty Shift+Del, we have a quick solution to prevent further mishaps. You can use chattr to change the associated attributes for a file. The default syntax is chattr [operator] [switch] [filename] . Refer to the man page of chattr for a list of all available attributes and their purpose. For now, we’re only interested in the immutable attribute, which can be used to make sure a file cannot be deleted by any command, even by a root user. Run the sudo chattr +i filename command to set the immutable attribute. You’ll find that you can no longer delete the file, and you can’t edit it either. Run lsattr filename to view the attributes of the specified file. sudo chattr -R +i…

GNU Radio is a free and open-source software development toolkit that has generated interest in research, industry, academia, government and hobbyist environments. It enables the construction of complex testing scenarios without the need for test equipment. Note, however, that GNU Radio performs digital signal processing of an analogue signal. A Block may produce a 1kHz tone, but it is not an analogue signal. It is an analogue-to-digital decoded (ADC) representation of the signal. The GNU Radio software is not manipulating the analogue signal itself but rather the digital representation of the signal. The learning curve for GNU Radio is not only steep but also broad. The documentation provides tutorials and flow graph code samples to get started, along with some suggestions for those new to the world of digital signal…

Timing is critical. It is important to make sure all your devices report the correct time. Not having the correct time can cause many issues, not least with certificates, LDAP and others. By default, UK readers will have the time set to UTC, which isn’t actually a timezone. There is a new tool to manage time – timedatectl. To set the correct timezone, just set it using the command: $ sudo timedatectl set-timezone Europe/London Obviously, for those in other timezones this may not be an issue or will require a different timezone. Alongside this, setting the time in a small environment is quite simple. Using the timedatectl command by itself will show the time, time zone, etc. as well as the status of the time sync. If this is set…

During part two of the tutorial our docker-compose.yml file has grown in size and complexity. If you want to save typing in each line, scoot over to the project Github respository at https://github. com/prel-im/lxf261, where you will find a final version of the file. Remember to change the hostnames for your environment! In addition to being packed full of functionality, Traefik is also very well documented. Take a look at https://docs. traefik.io for everything from concepts/ tutorials through to detailed reference documentation for each feature. Part one, what part one? Head to linuxformat. com/archives to grab the tutorial from LXF259.…

When developing a Node.js application you need to set it for logging and debugging. This happens in your code, and you direct it to standard out. It is always better to direct all logging to standard out and let external tools route and filter where the logs go. Once you have done that you can read the logs directly from your console, which is fine to start with. As soon as you have several modules and many views, you rely on many libraries. This adds complexity really fast, and one of the first areas where it shows is in the logs. You will end up digging through logs for most of your time. For this to work, you need a module that shows you the faults – the built-in stuff…

All the examples in the main part of this tutorial generated results purely within LibreOffice Calc, using the laws of maths. However, it is also useful for creating graphs of experimental results, perhaps combined with equivalent results from simulation studies generated elsewhere. Calc offers several facilities that would be beneficial here. First of all, it’s especially useful when displaying several datasets on a single XY chart that some can be shown as lines, while others can be shown as points. This allows experimental results to be shown as points, because intermediate values should not be interpolated, yet simulated results could be shown as a line where intermediate values are meaningful. Second, it is possible to show error bars – often required when showing experimental results. And third, trend lines can…

Logstash is a tool for managing events and logs. Usually, Logstash stores the data it collects in Elasticsearch, so that it can be processed and visualised. Additionally, Logstash can process data before sending it to Elasticsearch, which can be good when dealing with lots of data generated by very busy servers. This will not only make the visualisation process much faster, but it will also make the storing process faster. Logstash can accept data from many sources (inputs), process it and forward it to any of its available destinations (outputs). The list of inputs includes plain text files, Kafka and Elasticsearch – each input is supported by an input plugin. Output plugins (www.elastic.co/guide/en/logstash/current/output-plugins.html) work the same way for generating output. The path of the Logstash configuration file is either /usr/share/logstash/pipeline/logstash.conf…

Linux Format is 20! How did that happen? We drag all the ex-editors kicking and screaming into a pub and ask them exactly that. Education USA style The Raspberry Pi has helped kickstart a UK computer revolution. We look at how that’s being transferred to the USA. Desktop wars: which is the best? We love a good argument, so tell us why we’re wrong when we award Gnome or KDE or something else best desktop 2020. Get into game coding We kick off a new coding series that promises to teach you code and how to write games, all at the same time. Madness. Contents of future issues subject to change – we might be too drunk from all the “celebrating”.…

“ Linux beginners and seasoned users alike oftentimes run into difficulties with home directories. Maybe simple permissions artefacts from running things as root. Maybe the classic forgetting a slash when trying to copy a directory and ending up with /home/home/jonni or something. Or maybe catastrophic data loss doing something else. Anyway, there’s a new way of managing home directories coming to town, and we suspect some of you will feel shivers run down your spine when you read the next paragraph. Systemd-homed aims to modernise home directory management on Linux. It aims to ease directory migration, streamline encryption and introduce a modern JSON user database. It will be merged into the next Systemd release (245) and picked up by distros as they see fit. I think some of this is…

Liberapay (https://en.liberapay.com) is a recurrent donations platform that allows people to help fund creators and projects online. It’s celebrating its fourth birthday, and in a blogpost (which can be read at http://bit.ly/LXF261Liberapay), the team have announced that the much-requested feature of enabling automatic renewals for donations has been implemented. While the blog post warns that the feature is “very new and still rough around the edges,” it means donors can set up recurring donations to provide a stable income for creators and projects. Users can now set up recurring donations via the new Payment Schedule page. At the time of writing, this feature only works with Stripe, and not PayPal, but that should hopefully change in the future. Other new features coming to Liberapay include grouped payments – where you…

“ For remote security surveillance, like monitoring an industrial facility where equipment or human lives might be at stake, maintaining an immediate and high-quality video stream from the areas of interest is a must. With the advent of 5G networks, it’s possible to stream high-quality video in real time with very low latency, which wasn’t possible with past generations of mobile networks. In this domain, the SRT open source protocol has been picking up momentum, and thanks to the elements available since GStreamer 1.16, it’s easier than ever to incorporate low-latency streaming into your app. At Collabora we’ve been participating in the design and development of Hwangsaeul – a next-generation security video feed streaming platform with SK Telecom Co. It’s a cloud relay service that gathers live security video feeds…

Yi L Liu posted a patch series titled “Export device’s PASID capability to VMs”, which aims to enable support for Shared Virtual Memory (SVM) within virtual machines on Intel platforms. SVM enables a device and host (or in this case, guest) operating system applications to share the same virtual view of memory without needing special drivers in each instance. Eventually, it will enable applications to talk to plug-in cards without special drivers, which is very useful if the plug-in card is a flexible device such as an FPGA, that would otherwise require many different device drivers for every possible function. Paolo Bonzini posted a security patch correcting support for TLB flushing within guest VMs. TLBs (Translation Lookaside Buffers) cache translations between virtual (as seen by an application or VM) and…

Most distros now use systemd as their service manager, but systemd does a lot more than just manage startup services. One of the extra features is that it replaces the traditional system log with a journal. The journal is indexed for faster searching, which means that it is no longer a pure text file that can be read with a pager like less or searched with the likes of grep. Instead you use the journalctl command, which comes with a number of useful options, For example: only shows journal entries with a priority of error or higher, useful when trying to find problems; shows the journal entries since the last boot. You can follow this with a number to select a different boot – 1 shows the first boot in…

AMD’s retail Radeon RX 5500 XT series of graphics cards is here, bringing additional options to the budget and mid-range market. AMD’s Navi architecture hasn’t changed, although Navi 14 cuts the potential number of compute units from a maximum of 40 down to a maximum of 24 – with the 5500 XT enabling 22 of those CUs. There are two versions of the 5500XT; the only difference is the VRAM and a £30 increase in price. The 5500 XT 4GB card matches up against the GTX 1650 Super, and the two are effectively tied in performance. The 8GB card, meanwhile, has to take on the GTX 1660, and Nvidia’s card has the same number of GPU cores: 1,408. The problem for AMD is that Nvidia’s GPU cores tend to perform…

There are several approaches to data visualisation that differ in the level of scientific complexity. However, you don’t have to be a scientist to visualise some simpler things in life, like kids’ school (downward spiral?–Ed) performance or money spending. As such, we’ll leave powerful systems as MATLAB aside and give more favour to WYSWIG tools and editors. Finding a perfect balance between a rich set of features and a novice-friendly GUI sometimes sounds alike an impossible mission, but we feel that some of our contenders come very close to perfection. We’re going to evaluate how our contenders perform with CSV handling, drawing custom plots, block schemes and diagrams, and also what it takes to get used to them and take a right step towards being proficient in plotting. There is…

In many cases plotting is assumed to be the same as drawing schemes and plans, which is very close to what vector-graphics editors do. Still, it’s always good to have an application that can properly connect boxes with arrows, automatically add text captions to drawn objects, and so on. In this regard most of our plotting apps performed very well. LibreOffice has a dedicated part with a simple name, Draw, for doing vector graphics with some advanced features like connectors, object aligning, node editing and more. Veusz is all about graphs, but it also lets you draw lines, rectangles, polygons and ellipses. Drawing isn’t the primary feature of Veusz, but you can nevertheless do a some basic stuff with it. In terms of drawing, Jade is more advanced than Veusz.…

You might gather by now that QEMU incantations can get quite unwieldy once you start avoiding defaults – so it’s common for people to store these in a script, or use some kind of frontend for QEMU. The modern way to wrangle this is with Red Hat’s Libvirt. This isn’t a frontend – we’ll meet Virtual Machine Manager soon, which is – but rather an API that provides access to virtualisation functions through its daemon, libvirtd. Libvirt supports a number of hypervisors, including KVM and VirtualBox. This might seem, to the layman, like adding another layer of complication on top of something that’s complicated enough. That’s a reasonable point; if you just want to set up a VM to try the occasional Linux distro, it’s easy to do with VirtualBox…

First, navigate your way to the Ports Collection on your machine: A Port is basically a recipe for building the program in question. Spin through the various sub-folders and you’ll start to see some old friends, such as desktops in the /x11-wm folder, the Firefox browser in /www, and (huzzah!) Emacs in /editors. In order to search for applications, we first need to index all the ports in the system: Use the following command to search for something: This will show you the name, location and a short description for your results. If you find what you want and would like to install it, you can use the command below. Just bear in mind you’ll be compiling, not just installing, the application and all its dependencies. To build and install…

Lifeograph supports simple to-do lists within diary entries. Use the List button to set one up. You’ll see four box options: to-do, in progress, done and cancelled. Once this list is in place, update each box simply by clicking it once to cycle between the available options screen. You’ll also find another hidden file with a ~previousversion file extension. This is a backup version that contains the diary’s content prior to the last editing session – if you wanted to roll back to this version, the procedure is the same as for the ~LOCK~ file, except this time you want to rename the ~previousversion with a .diary extension instead. Lifeograph supports another level of chapter organisation in the form of categories, which work in relation with date chapters to let…

We’re going to take an in-depth look into the instructions for installing and using the GNU Radio software on a standard Linux desktop. GNU Radio is an open-source software development toolkit (SDK) that replaces physical test equipment and electronic circuitry – usually found in an electronics labs – meant to generate and/or process analogue signals. It can simulate the audio source in software and then play the audio tone from the digital source using the PC’s sound output: no need for the audio generator and breadboard circuits! We’re going to install GNU Radio on a computer running Ubuntu 18.04 and provide the basic knowledge required to construct an analogue audio circuit with the software. From a command line, enter the following commands to refreshes the OS to ensure all repositories…

While in this introduction we have looked at information that can be gathered using properly installed agents, getting information from appliances presents an obvious problem – there are no installing agents on them. Fortunately, there is a solution to this problem. This is where the SNMP protocol comes into play. SNMP, or simple network management protocol, works in a very standardised way and is vendor neutral. When installed it allows the data to be pulled into tools such as Zabbix. While there is the SNMP protocol, there’s also the MIBS (management information base) that go along with them. These are essentially installable modules that vendors produce to enable the data on the appliance or other hardware to allow the data to be brought into the system in a standardised way…

Let’s Encrypt launched in 2016 and offers both individuals and organisations a way to obtain completely free TLS (historically called SSL) certificates, allowing traffic to be encrypted between a web browser and server. Let’s Encrypt makes use of a challenge-response protocol (called ACME, we see this name mentioned in the Traefik configuration files) to verify that the certificate request is legitimate. For instance, if you were to send a request for a certificate for nextcloud.prelim.xyz the service would send a challenge to that address. Assuming you own the domain and your server is reachable, you have effectively proved ownership of the domain and a certificate will be issued. The service has grown massively in popularity, with nearly a billion certificates issued by the end of 2019! SSL/TLS certificates used to…

Before you start using all the tools, learn a few grep tricks, they will help you use more advanced tools. The simplest is to look for the word in all files; grep -r memory /var/log . You will then have a result full of memory events. To see how much space your log files take on the disk, you can use the du & df commands. The simplest is to use du -csh /var/log/ you will see one value; the amount of disk space that all logs use. When you are interested specifically in the network interfaces, ‘nield’ is a strong alternative. It logs all serious network events regarding interfaces, routing and your IP address.…

GUI FOR YOUTUBE-DL Tartube Version: 1.3.048 Web: https://github.com/axcore/tartube Youtube-dl is one of the most important CLI tools for everyone fond of downloading videos from YouTube. The Youtube-dl repository on Github is flourishing with hundreds of contributors and thousands of commits. No wonder that many video players often integrate this utility to provide an extra feature of playing media ‘directly’ from YouTube (though the content is silently downloaded first). There is no visible lack of graphical frontends to Youtube-dl, but we think we have found the most advanced and complete one – Tartube. This application is based on Python and GTK3, and it provides a clean and developed interface for managing videos. In particular, Tartube can sort your downloads in several folders, download whole channels and playlists, and lets you define…

LibreOffice Calc provides lots of options for formatting charts. Included here are line styles, thicknesses and colours, marker types, sizes and colours, axis formatting and so much more. LibreOffice includes a utility – the Math Formula Editor – which allows you to create equations. You can use it as a stand-alone utility or from within Calc where you’ll find it at Insert > Object > Formula. It might be quite a mundane use, but have you considered using LibreOffice Calc as a scientific calculator? You might not even bother saving your result, just type the formula you’re interested in to see an immediate result.…

Kibana offers analytics and a search dashboard for Elasticsearch, as well as visualisation capabilities for data stored in Elasticsearch. Kibana is so handy that it would be a shame to use Elasticsearch without combining it with Kibana. Generally speaking, you will not need to work so much with Elasticsearch directly as you will use Kibana to get and process data stored in it. However, knowing how to execute queries in Elasticsearch can be handy for troubleshooting. When using the default port number, Kibana can be accessed by your browser via http://localhost:5601 or http://hostname:5601, in case you want to access it from a different computer. It’s a good idea to know some Kibana terminology. An index pattern tells Kibana about the Elasticsearch indices you want to work with. A dashboard allows…

USING THE LXFDVD Using Linux for the first time can be very confusing. It’ll be unlike anything that you’ve likely operated before, especially if you’re used to Microsoft Windows or Apple macOS. Generally our DVDs are designed to be run directly, which is to say that when you first power on your PC (or Mac) it should ‘boot’ from the DVD – so before Windows or macOS even starts to load – with Linux running directly from the DVD. This trick is known as a Live Disc. It enables you to try out the various versions of Linux without having to install or change anything on your PC. Just remove the DVD, restart your PC and it’ll be exactly as you left it. While many systems will boot from a…