Linux Format的December 2020目录

Jonni Bidwell My life has been improved by starting each morning with a handstand. Also, the Spotify Connect plugin for Volumio allows my whole household of misfits and vagabonds access to the kitchen hi-fi. Wait… that only makes for an eclectic day. And possibly complaints from the neighbours. Christian Cawley My hack for a better day when you’re working from home with the family milling about is blues music. It takes me away into someone else’s sorrow, a journey that drowns out the inanities of domestic life and helps me focus. Les Pounder My life hack is to standardise your mobile kit. Have a USB powerbank that can charge your devices, and a cable for each. I have a lot of micro USB devices and two USB-C devices, all of…

“I typed, “Best regards, Keith” at the end of an email but, just as I hit the “h” of “Keith”, my finger caught the V key. Muscle memory made me send the email automatically. I had just signed myself “Keithy”. To a client. Argh! Now what? Say nothing, and hope they don’t notice? Or send another mail apologising, and drawing their attention to my error? I decided to send a follow-up mail to Tim, the client. Of course he understood immediately. He even had the decency signing his reply “Timmy”. Good man. No one wants to make mistakes. No one wants to work with others who make mistakes. But there are degrees of mistakes. Ultimately, my typo was embarrassing for about five minutes, but also harmless. However, where the cost…

“The past month included a discussion on the Linux Kernel Mailing List (LKML) of some exotic uses of the ext4 filesystem. It began when Josh Triplett posted that later Linux 5.9-rc kernels had broken in an unusual use case, which led to a discussion on what guarantees filesystems offer in terms of compatibility, as well as how Linux developers interpret their commitments to unusual uses. This reminded me in some ways of my earliest days using Linux. I was running Slackware in the mid-late 90s and would often uncleanly power off my machine. This was in the days before journalled filesystems. Today, we use journalling to handle unclean shutdowns transparently. Your machine “replays” the latest changes on next boot to clean things up. In those days, your system might run…

Q Use the source As with all previous versions of Ubuntu since Ubuntu 16, I haven’t been able to get my printer to work. It works fine on Ubuntu 16 and Mint 17, but not with later versions for various reasons. My latest attempt on Ubuntu 20.04 failed early on due to not being able to install the driver supplied in a tar file. The usual paths of ./configure or ./install.sh don’t appear to be available on Ubuntu 20.04. With time running out for support for Ubuntu 16 I need your help on this Ubuntu 20 problem. How can someone without a degree in Linux brain surgery (me) make ./configure and ./install.sh available on Ubuntu 20.04? John Bourne A The path ./ refers to the current directory, so ./configure…

While it’s true that the distributions in this Roundup are loaded with tools for penetration testing that you can use to compromise your own network, it doesn’t mean that you’ll be able to identify the weak points of entry simply by booting into their respective Live environments. A pen-testing tool will be of little use to anyone who doesn’t have the required know-how to operate them. Like any specialised distro, it’s natural for the projects to assume their users know what they are getting into. Some distros, however, just expect users to be familiar with the entire landscape. This isn’t the right approach to building toolkits like these pen-testing distros and we’ll not look favourably towards distros that make too many assumptions about the users. Furthermore many of these tools…

There are quite a few pen-testing distros out there and we’ve already covered the ones that are actively maintained in this Roundup. A better bet instead would be to look for pen-testing tools inside security-focused distros that might also include tools for digital forensics. For instance, there’s CAINE that’s designed as a digital forensics distro, but can be used for some pen-testing tasks as well. The distro had a stable release back in December 2019. There’s also Network Security Toolkit, which is a Fedora-based distro that primarily focuses on network security and has a web-based user interface. Even Fedora has a Security Lab spin that bundles a lot of pen-testing utilities. Arch users can also use the Arch Strike repository to infuse pen-testing tools in their Arch installations. One interesting…

There’s a school of thought that says we (or anyone) shouldn’t provide information that budding hackers could use to cause damage or distress. Barnes and Noble took such umbrage to our Learn to Hack feature in 2012 that the whole issue was stricken from its shelves. In February the UK’s West Midlands Regional Organised Crime Unit even launched a poster campaign naming and shaming Tor, Kali Linux and Metasploit, and urging parents to check their children aren’t turning into evil hackers. But we think differently. By understanding these techniques and having tools at our disposal to execute them in a responsible way, we can help create a more secure computing space. Penetration-testing is big business nowadays and companies pay more money than they’d like to admit to have people (red…

HAVING FUN WITH DVWA “We’ve borked the underlying SQL query and tricked the application into coughing up usernames and passwords for the whole team.” Part of our last hacking feature in LXF258 involved setting up the Metasploitable virtual machine and attacking it. We’d encourage you to do that too, (you’ll find all the information you need at https://github.com/rapid7/metasploitable3). But this time around we’re going to do something different. The Damn Vulnerable Web Application (DVWA) is exactly what you might suspect. It’s a PHP application riddled with security holes (so, the LXF website?–Ed). It requires a LAMP (Linux Apache MySQL PHP) stack to run, and it’s certainly not the sort of thing you want to deploy on an Internet facing server. So rather than set all that up from scratch, we’ll…

Before you begin you might want to familiarise yourself with Zulip by setting up a free account at https://zulip.com. The free plan gives you a not-inconsiderable 10,000 message history and 5GB of storage, as well as a nice URL of the form https://your-org.zulip.com for easy access to your organisation’s communications. The two key bits of terminology to grasp are streams and topics. Streams are a broader hierarchy and can be thought of as separate chatrooms. Different members of your team can be members of different streams, and streams can be made private so that only certain people can see them. Within a stream every message has its own topic and conversations will appear threaded thusly, rather like email subject lines. However, unlike email subject lines you can’t be lazy and…

No one expects a surprise Pi release! Without warning the Pi Foundation has released a vastly updated version of its industry-aimed Compute Module. The new release isn’t a huge surprise in itself, but the 16-month wait since the original Pi 4 launch and the huge update to the Compute Module itself are. So what’s new? We have a full run down of the specification below, but the core changes are the move to the Pi 4’s 1.5GHz Cortex-A72 SoC and all the goodness that brings, the addition of a PCI Express 2.0 bus and a change to the physical size of the board. The original Compute board was in a SODIMM form factor. This new version has been shrunk to 55x40mm with four physical mounting holes at each corner. Broadcom…

OUR EXPERT Mats Tage Axelsson has spent decades figuring out reasons to use Linux computers while sacrificing real social interactions. Embedded systems are small, specialised units with a key attribute being their robustness. You can build them for automation tasks, robots and monitoring. You can also boost machine learning and artificial intelligence using an embedded system for extended training sessions out in the field. With both networking and pins for input and output, you can use embedded systems to monitor weather and soil quality, for example. There’s a huge range of expansion boards that can sense light, sound and gases, enabling them to be used in an almost limitless range of real-world detection and monitoring scenarios. What the Raspberry Pi started for home makers was nothing short of a revolution.…

It’s crucial that you eject the microSD card before disassembling the RasPad 3. If not, you risk damaging the card or the card slot. With a broken card slot, the Raspberry Pi can’t boot and your RasPad is useless. Or is it? Fortunately, there’s a workaround. This happened with the test unit after a couple of days’ use, and the resistance from the SD card and slot was almost impossible to detect. This isn’t a case of having to use excessive force – it’s simply a delicate component. It’s also common sense to remove the card first. Guilty as charged, your honour. First, power off the RasPad and remove the microSD card. Next, detach the broken microSD slot. This avoids it breaking off completely later and rattling around, likely shorting…

OUR EXPERT  Nick Peers has been busy building a huge audiobook library from his massive CD collection, all powered by the lovely Booksonic. We all love a good story – after all, telling stories around the fire is as old as human language itself. Audiobooks – and radio dramatisations – continue that tradition into the modern age, and thanks to your phone and PC, give you the opportunity to listen to your favourite books wherever you are. In this guide, we’ll show you how to bring all your audiobooks – whether on CD or in the cloud – into one central library. You’ll add tags to make them easy to identify, plus discover how to listen to them from your PC or phone. Let’s get storytelling… Set up your Audiobook…

To hunt down artwork for your audiobook, head to https://images.google.co.uk and search for the title of your book plus the word ‘audiobook’. You’ll almost certainly get a match, but wait – is it suitably hi-res? Our preferred size is 600x600 pixels, although 500x500 is the size of artwork embedded into your Audible collection by OpenAudible. To locate higher res artwork more easily, click Tools under the Google Search button and change Any size to Large, which will filter out smaller images. Hopefully at least one will remain: click it to view a preview. Roll your mouse over this to reveal its size – if large enough, right-click it and choose ‘Save image as’ to save a copy to your hard drive. Use your image editor to reduce both its physical…

OUR EXPERT  Les Pounder is associate editor at Tom’s Hardware and a freelance creative technologist. The ringing of the school bell in the 80s didn’t only signal break time – it also marked the start of a computing conflict. It started over which eight-bit computer was the best. Commodore kids battled Spectrum fans, Amstrad kids launched their surprise attack! But when the 16-bit machines came along, those battlelines were forever changed. Commodore had its Amiga range of computers and Atari had the ST, but both shared a common CPU – the Motorola 68000 – and a similar form factor. The Atari ST obviously didn’t have the custom chips found in the Amiga, but it did have a small headstart on the Amiga, due to a number of legal wrangles in…

Primarily designed for creating games, STOS is a dialect of BASIC for the Atari ST that offered users the chance to write applications using the well-known language, while also adding extra features made possible by the added power of the 16-bit era machines. Sprite creation, music and image manipulation were all made possible with STOS. It was originally created by François Lionet and Constantin Sotiropoulos, and was first released in France before version 2.3 was released by Mandarin Software (now known as Europress). In this era, BASIC was still a popular language for beginners and general-purpose computing, and STOS filled the gap that Atari ST BASIC had left. It may not have been as advanced as GFA BASIC, but STOS left a legacy in the programming world. It directly influenced…

OUR EXPERT  Alexander Tolstoy hides secret messages in underexposed parts of his photos. There are much easier ways to order pizza, though. Shooting in RAW opens up a whole world of new possibilities in digital photography. RAW images contain more information about colours that we can use to improve image quality. In the first part of this tutorial we fixed exposure, white balance and grain noise. This time we’re moving forward with another set of improvements, specifically chromatic aberrations, dynamic range compression and local adjustments. We’ll also explain how to remove unwanted vignetting and haze. Even though digital cameras are getting better all the time and their firmware algorithms deliver perfectly acceptable results in Auto mode, there are still image-editing tasks that you can do better manually. Note that this…

1 Drawn mask options There are five types of drawn masks in Darktable: brush, circle, ellipse, path and gradient. This should give you enough choice to select a particular region or shape on an image. Drawn masks can be scaled or re-shaped, just like vector objects. 2 Adjust the mask type When it’s not possible to select, say, the outdoor hockey ice field without the same-coloured grey sky above it, use a parametric mask to select both and then cut away the area you don’t want to adjust with a drawn path. Combining two mask types into one can come in handy! 3 Manage your masks Darktable keeps record of all masks you’ve used within a project. It’s easy to switch masks or add more adjusting tools…

OUR EXPERT  Calvin Robinson is a former assistant principal and computer science teacher with and a degree in computer games design and programming. Over our series of tutorials for games programming in Python, we’ve created a Lunar Lander-style module game, a side-scrolling platformer, Pac-Man, Pong, Game of Life and a shooter. This issue we’re going to recreate another classic, Snap! Traditionally a card game, the game presents a number of images and the player has to react with haste in order to win. Since we’re developing an electronic version of Snap, we’ll use emoji images instead of playing cards, but you could also adapt this to suit your personal preference. First, we’ll need to make sure that we’ve got Python downloaded and installed. On a Debian-based distro it’s a simple…

OUR EXPERT  Mihalis Tsoukalos is a DataOps engineer and a technical writer. He’s the author of Go Systems Programming and Mastering Go, 2nd edition. The subject of this tutorial is two-fold. First, it’s about creating a Go application that exports metrics to Prometheus, which stores them Second, Grafana reads the data from Prometheus and generates beautiful visualisations. The environment used in this tutorial is constructed using Docker containers. So we’re going to need a Docker image for the Go application, another one for Prometheus and a third one for Grafana. The Go application will obtain the output of the uptime command and extract the three load averages as well as the number of users in the Linux machine. This means we’re going to send four counters to Prometheus. Because we’re…

The easiest way to get hold of Grafana and begin using it as soon as possible is by downloading and executing its official Docker image. This means that apart from the Docker image, you won’t need to download, set up or install anything else for Grafana to work. However, you’re still going to need to define the port number that Grafana will listen, together with the local directory where Grafana will store its files. To plot data you first need to obtain that data. In the case of Grafana, data comes from one or more data sources. A Grafana data source can be a database, file or service that provides data to Grafana - the program can’t operate without data. A Grafana Panel is the basic building block of Grafana.…

USING THE LXFDVD Using Linux for the first time can be very confusing. It’ll most likely be unlike anything that you’ve 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, see below) 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…

Each year we proclaim it’s time to learn how to hack. But why? Jonni always gets angry at the subversion of the term ‘hacking’ and I can understand why. Hacking is fun, as is finding out how systems work and how to get them to do things they were never meant to do. With open source and the Linux ecosystem there’s an abundance of hacking fun to be had, and it’s no wonder all the key tools for learning how to hack – and actually hack – are developed and run out of Linux systems. For this year’s look at the world of hacking Jonni’s introducing you to the metasploit framework. This is a playground where you can learn, explore and develop hacking skills. It’s usually paired with Kali Linux,…

Back in LXF267 we reported how the US Agency for Global Media (USAGM) had ordered the mass firings of the CEO and senior officers of the Open Technology Fund (OTF), a US government-funded organisation whose aim is to offer uncensored access to the internet to people around the world, especially those in oppressive regimes. The move raised concerns at the time that the supposedly independent and bipartisan USAGM was being politically motivated under the instructions of Trump Administration-appointed Michael Pack. It appears a Superior Court judge in Washington, DC – who was also appointed by the Trump Administration – agrees, ruling that Michael acted illegally in his attempts to get OTF employees fired. Judge Shana Frost Matini, in a Superior Court Order (which can be read in full at http://bit.ly/LXF270USAGM),…

Purism, the company creating the Librem 5 smartphone that runs PureOS, has launched a website (https://puri.sm/fund-your-app), enabling future owners of the handset to vote for which apps they’d like to help develop for the phone, along with an option to donate money for the development as well. The idea is that Purism can gain an idea of what apps users want to see, and prioritise its work accordingly, while Librem 5 owners get to have a say on what apps, including popular ones such as Uber, Waze and Google Maps, they want on the smartphone. Win, win, right? Well, maybe not, because some Librem 5 owners are questioning why they’re being asked to fork out more money to help get these apps on PureOS when they’ve already spent over the…

Linus Torvalds announced the final release of Linux 5.9. The latest Linux release has many great new features, among them a number of memory management enhancements, and a new “close_range()” system call that enables applications to close a bunch of file descriptors all at once. Memory management changes include tweaking how Linux handles “anonymous” memory (memory that’s not backed by a file on disk). It used to be the case that anonymous memory (for example, allocated with malloc ) could potentially cause actively used data to be paged (swapped) out to disk, especially on busy machines. It will no longer take preference in that case. With the release of 5.9 came the opening of the “merge window” (period of time during which disruptive changes are allowed into the kernel) for…

RAID is a means of combining several hard disks, or partitions, into one device to either boost storage space or reliability, or both. Generally all devices should be the same size. You can buy hardware RAID controllers but the Linux kernel does it well in software. The main RAID levels RAID0: two or more disks combined as one big disk, but has no redundancy. One disk failure can lose all your data. RAID1: two or more (even numbered) disks are mirrored. It has the same capacity as one of the disks, but can survive failure of all but one of them. RAID5: Three or more disks are combined in such a way that all data is on at least two of them. A RAID5 setup can survive failure of one…

Jitsi a minute I’ve just finished deploying Jitsi Meet to my home server following Jonni’s excellent tutorial. He makes the whole process impressively simple and clear, and it’s great to have the reassurance of a self-hosted open source solution. When it comes to tasks like this there are always plenty of tutorials available online, but many of them are poorly tested or out-of-date. The confidence of knowing the steps have been tested and produce working results adds real value as far as I’m concerned. I now have a bunch of useful services running on my home server – many of them prompted by one or other of your tutorials. I look forward to more in the future. David Neil says… Thanks for the kind words. I’m sure Jonni will really…

Kali Linux is by far the most documented project of all the distributions on test. Besides the official documentation that mostly deals with the distro, there are several books and lots of online courses that’ll help you become proficient with the bundled tools. While most of them have a list price, some of the books and courses are available for free as well. BlackArch 2020 has started work on a multilingual guide that helps you get started with the distro. The project does plan to write a whole section on the bundled tools. While there are no forum boards, you can engage with the developers on IRC as well as on the project’s discord channel. Parrot Security 4.10 has different user guides to help you get started with, use and…

Te 1995 film Hackers has a lot to answer for. Not only was there egregious product placement for a certain fizzy beverage with red and white branding, but it helped reinforce the notion that hacking was all good-looking edgy types breaking into other people’s computers and causing havoc. Today that notion (along with the idea that an oversized black hoodie and V for Vendetta mask are essential attire for this hacking) is fairly entrenched among the non-tech savvy, ever the more reinforced by so many unlikely movies and shoddy media reporting. Readers of this fine publication ought not to buy into that. “Hacking” originally meant the breaking, modifying and repurposing of technology so it functions differently to how the manufacturer intended. Today, many programmers call themselves hackers, and only a…

Apart from expanding my understanding of the Linux command line, using the Pi stimulates creativity and innovation. This often revolves around realising wacky ideas such as, can I make a game of battleships with 100 LEDs in glass bottles and an old GPO rotary dial telephone (www.tecoed.co.uk/battleships.html) or perhaps the more useful upcycled IKEA hologram table (www.youtube.com/watch?v=7pNxikwtCvs)? I’m constantly impressed at how versatile the Pi is enabling you to create projects. There’s a lot of satisfaction to be had working on a project, learning to understand APIs, components and code to control them. As an educator I’ve observed success through the integration of the Pi within the classroom. Even the most disaffected student has been absorbed in writing a few lines of code to control a motor or to enable…

OUR EXPERT Les Pounder is Associate editor at Tom’s Hardware and a freelance creative technologist. He blogs about his discoveries at bigl.es. And clearly watches too much Star Trek. The other day, while watching the episode of Star Trek: The Next Generation where Captain Picard was trapped on a planet with an alien who only spoke in metaphors made us think: “Hey we do that now with memes!” Memes are all over the Internet and they’re great fun to drop into a tweet. With this project we can make our own meme images using Python and a module named PIL (Python Imaging Library). To make it all a little easier for users we shall also make a simple GUI. Software setup PIL comes pre-installed with Raspberry Pi OS, but we…

When using an embedded system as a media centre, you need to know about NFO files. The files keep track of the meta data for your titles. They’re XML files that contain information on the song, movie or other media that you’re accessing. For example, an XML file on a film will contain the title, run time and genre. Because it’s stored under a category tag, you can use it to list and sort your files. This makes it easier to find the media to suit the occasion. The big media distributions use this format to store all this data. IMDB and other services use their own, but Kodi and similar make use of ready-made scripts to scrape data from the sites and convert it into NFO files. Once this…

OUR EXPERT  Shashank Sharma is an avid Arch user and a trial lawyer based in Delhi. He’s always on the look-out for geeky memorabilia. Your Linux distribution is home to several nifty command-line utilities that can be used to report a variety of useful information. Everything from hard disk RPM, CPU temperature, network speed and more can be learnt with a single command. While we may well cover these utilities in future issues, our focus for now is on utilities that will reveal pertinent information about disk space. If you’ve ever wanted to learn about the total disk space used and available on any given partition, the space used by different files and directories, and how you can free up space on your disk by identifying files which haven’t been…

Want to listen to audiobooks on your Android phone? If you’ve followed our guide to setting up Booksonic in LXF259, then the obvious solution is to install the official Booksonic app (£2.49), which not only streams books from your server to save space on your phone, but enables you to mark individual titles for listening to offline. This means that they’re temporarily downloaded to your phone’s storage, which makes it possible for you to listen to them anywhere, then easily removed when you’re done. If all you want is to listen to audiobooks you’ve transferred to your phone’s storage – after all, you can fit a heck of a lot of books on to a 32GB microSD card – then try Smart AudioBook Player instead. When you first launch it,…

Rastari works with all models of Raspberry Pi up to 3B+. It’s a great way to reuse an old Pi that’s gathering dust in the box. The Pi can also be housed inside an ST case if you have the skills and a broken ST to hand. Saving the config of your emulated Atari ST is a smart move. The config can be reused at a later date and it’s essential if wishing to use different models of ST or specific applications. In the Hatari emulator we can access a hidden menu at any time by pressing F12. This launches the Hatari main menu, used to configure the emulator and to insert floppy disks.…

OUR EXPERT Nick Peers spends most of his Linux-related time in Ubuntu, and loves the LTS versions because he doesn’t have to upgrade every six months! An operating system stands or falls on the quality of its programs, and Linux is no exception. Thankfully, you’ll find a rich seam of applications spanning all your needs, and we’ve dug out 10 of the absolute best to help you get started. Unless stated, all programs can be installed through the Ubuntu Software store app, but where multiple versions exist, choose the Snap version, which will ensure you’ll always have access to the latest version. VLC Media Player Ubuntu’s built-in Videos tool is good, but it will struggle with more demanding movies – for example, it can struggle with 4K video encoded using…

Vignetting is an inevitable feature of most camera lens, when there’s a reduction of an image’s brightness towards the periphery compared to the image centre. Generally, the larger the size of the aperture (and consequently the smaller the F-number), the more obvious the vignette effect. That’s quite natural since a smaller F-number also causes a reduced depth of field and helps isolate the object in the foreground, drawing the viewer’s attention to it. However, if you want to shoot landscapes with an open aperture, or take photos of something that has important elements near the frame’s edges then vignetting needs to be avoided. The four major RAW editing applications in Linux handle vignettes differently. Lightzone has no such tool at all while Aftershot Pro has only a manual vignette compensation…

MUSIC PLAYER Nuclear Version: 0.6.5 Web: https://github.com/nukeop/nuclear Among the dozens of YouTube downloaders that can be easily found on Github there’s the remarkable MPS-Youtube utility, which works as a command line music player for YouTube. If all you need is audio and you don’t care about video, this can be a great replacement for a convenient music player. However, MPS-Youtube naturally lacks a graphical interface, which would be really sad if it weren’t for Nuclear. This is an outstanding streaming music player with an attractive Spotify-like interface, plug-ins, lyrics finder and a great selection of bells and whistles that together will blow your mind. Nuclear fetches music tracks from Invidious, Soundcloud, YouTube and Jamendo, and displays the unified search results list that you can use to populate your own playlists.…

At the moment, our leader board is a list of scores. Consider supplying an input box so that each player gets an opportunity to add their name. The rules are simple: in 20 seconds find as many matches as possible. Each successfully match gains an extra five seconds on the counter. Clicking an incorrect match deducts a point. Snap was originally a two-player card game. So how could you adapt the digital version of the game to remove the computer-generated emojis and create space for another player?…

Prometheus pulls data from the data source. This means that Prometheus wants to know where to get its data from and the data source, which in our case is the Go application. Although this tutorial uses Docker images for Grafana, Prometheus and the Go application, you can install all software on your Linux machine as you do with other software and configure them according to the instructions of this tutorial. You can learn more about installing Grafana on Linux by visiting https://grafana. com/docs/installation. The official web site for Prometheus can be found at https:// prometheus.io . The Prometheus Go client library is at https:// github.com/prometheus/ client_golang. You can learn more about Grafana at https://grafana. com while the Grafana documentation site is at https:// grafana.com/docs.…

“For too long, Windows has been the sole platform for any serious gaming on computers. In fact, there’s still much resistance by game studios for supporting multiple platforms, which can be partially explained by the high costs of porting games to Linux compared to the number of users that can be reached. This is a Catch 22 problem for the Linux gaming ecosystem, where not enough gamers care about Linux to attract attention from studios, while the limited catalogue of supported games hinders Linux from attracting more gamers. At Collabora, we’re working with others to break this cycle and make Linux the platform of choice to run the games of today by improving the emulation support provided by software like Wine. We’re solving the issues Wine faces when emulating the…

“ClickHouse was developed for Yandex Metrics (the Russian equivalent of Google Analytics) as a data store and was Apache 2 licenced in 2016. In 2020. Altinity picked up $4m in funding to help it finish off a ClickHouse cloud service that’s in private beta. The project was originally created to handle the ad-click stream from Yandex’s ad network. It was designed to aggregate, transform, and make calculations on massive amounts of data, as well as ensuring real time access. For some use cases this open source project can reach performance benchmarks in the billion-rows-per second. What makes ClickHouse special is that it’s frugal on the bytes per row, saving on disk and memory space, and CPU processing. It can also parallelise a query through all CPU cores and distribute a…

Andrea Righi (Canonical) posted a patch series titled “Opportunistic memory reclaim” which attempts to give userspace (programs) a means to inform the kernel that it should begin to free up physical memory (known as “reclaim”) because large allocations are likely in the near future. An example given is the need to allocate memory for imminent hibernation, as in the case of cloud computing “spot instances” being preempted. The replies noted that Shakeel Butt (Google) already has something similar in the works in “memcg: introduce per-memch reclaim interface”. A lengthy back and forth is taking place around kernel support for the new x86 “MOVDIR64B” instruction, intended to accelerate the movement of 64 bytes (a single cache line in most Intel and AMD systems) from a source to destination address. Since toolchains…

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…

Apart from Covid-19, the biggest story of 2020 is perhaps the Twitter hack back in July. While other such break-ins don’t get the same amount of coverage, computer systems and networks are compromised at an alarming frequency. It’s a sad facet of the modern connected world that affects everyone from private corporations to government agencies. Battling the deluge of digital assaults is an always-on task. At the same time system administrators need to understand the potential security weaknesses in their infrastructure. While it doesn’t have the same feel as a Hollywood cyber caper, preventing computer break-ins is the unglamorous side of security that requires as much planning. These days it’s pretty routine for businesses to bring in security specialists and have them breach their network defences. In fact, in some…

As far as platform support goes, BackBox 7 produces an image only for 64-bit machines. The project also offers an Amazon AMI appliance, but that’s available only on request. Pentoo 2020 is one of only two distros in this Roundup that’s still producing images for the older 32-bit architecture in addition to 64-bit machines. The project puts out Daily images that haven’t been tested and might be broken, as well as Beta images that have had some testing. BlackArch 2020 has a mammoth 15GB ISO for 64-bit machines as well as a smaller netinstall image if you want to tailor your environment. There’s also a 35GB OVA image for virtualisation platforms such as VirtualBox and QEMU. You can also install the project’s tools on top of your existing Arch install.…

Port scanning is one of the most common first steps towards assessing the security (or attacking) of a particular machine. There are a few different ways of doing it, but they all involve attempting to open a connection to various ports on the target machine to see which ones have services running on them (for example, webservers run on TCP ports 80 and 443). Nmap is one of the most useful port scanning tools around. Fire up a terminal in Kali and run This will scan the 1,000 most common ports on which services are found. On a default Kali install no services should be running and that command should tell you as much. Nmap by default uses stealth scanning, which only partially opens connections. This makes it harder to…

Last issue we had the pleasure of chatting to Zulip creator Tim Abbott. If you missed it we’d strongly advise you check it out. Tim started the KSplice project (for rebootless upgrades) before it was acquired by Oracle and in some ways Zulip grew out of that. Zulip is a truly next-generation chat system. It marries the asynchronous benefits of something traditional like email, with the synchronous benefits of instant messaging. Thanks to its unique threading model, Zulip manages to sidestep the message overload now associated with both worlds. Originally a private beta, Zulip was acquired by Dropbox in 2014 and became an open source project. Since then it’s soared in popularity and has a strong developer community. If you look at the GitHub metrics you’ll notice that a huge…

As used in this tutorial, PIL is a great tool to use with images in Python. It’s simple enough to understand and results are easy to achieve. Let’s take filters for example. Filters can change aspects of an image and you will have used them with apps on your smartphone. PIL can use filters to blue, sharpen, smooth, emboss and enhance the edges of images. To use a filter we need to import the ImageFilter class from PIL and then pass it the filename of the image that we want to use. Then we apply a filter in this case we blur the image. Then we show the image. The filtered image can now be saved to a new file. Images can also be rotated, resized and manipulated all using…

OUR EXPERT  Christian Cawley’s wife wants a walk-in wardrobe. He doesn’t mind building one, but finds them difficult to pass on the stairs.. Portability and immediacy are missing from the Raspberry Pi by default. It’s hardly a surprise, though: the barebones nature of the Raspberry Pi package underlines its versatility. A common way to overcome both problems is to convert the Pi into a tablet. Various solutions have been developed for this, but Sunfounder’s RasPad kit is leading the field. New in 2020 is the RasPad 3 kit, which has been designed specifically for the Raspberry Pi 4 (priced $213, see www.raspad.com/products/raspadv3).You’ll also need a 16GB or larger microSD card, and an adaptor for installing the operating system. The potential to have an 8GB Linux powered tablet is in your…

On a long-enough timeline, everyone runs out of disk space. This is the law. While you can’t outrun this outcome, you can fend it off by being on the lookout for unnecessary files. For this tutorial, and because that’s the purpose agedu serves, we define files that haven’t been accessed in quite a while as unnecessary. The utility is offered in the default installation by most desktop distributions. You can, however, install it using the software repositories. If you’re running Debian/Ubuntu or a derivative distro, run the sudo apt install agedu command to install it. Users on rpm-based distros can similarly run the dnf install agedu command. Before you start looking up files that haven’t been accessed in a long while, you have to let agedu build an index of…

When it comes to assigning genres to your audiobooks, avoid the generic ‘Audiobook’ to come up with specific book genres like Mystery or Sci-Fi. Search www.goodreads. com to see how other readers have categorised a book, if necessary. Fancy turning your audiobook collection into a streaming server accessible from anywhere over the internet? Dig out your copy of LXF259 and turn to page 64 for our two-page guide to building and maintaining the perfect audiobook server using Booksonic. We’ve chosen MP3 as the file format for our audiobook library because spoken word recordings don’t require audiophile levels of quality. When you factor in the length of most audiobooks – many hours per title – the smaller your files the better.…

The Operating System or Tramiel Operating System takes its name from Jack Tramiel, the owner of Atari. It was an operating system for Atari ST machines, and was based upon Digital Research’s GEM UI and GEMDOS. TOS provided a means to work with the Atari ST, insert disks and basic file administration. It was a ROM stored on the Atari ST, unlike the Amiga range of computers that uses floppy disks to load the Workbench. Powering on the Atari ST without a floppy would trigger the machine to boot into TOS – a powerful and useful feature when hard disks were expensive and not commonplace. The issue for emulation is that TOS is a copyrighted property, which means we can’t legally use a TOS ROM with our Hatari emulation. To…

A little warning is required: if you take a photo in a thick fog, there’s no filter capable of restoring obscured details. However, if the fog is light, there’s a mild haze visible down a valley or a polluted urban area, or you take a photograph through a dusty window, there’s a good chance that the fog effect can be reduced. Both Darktable and Rawtherapee are equipped with de-haze tools. Darktable’s version lives in the Correction group – search for it in the ‘More modules’ list if it doesn’t show up by default. In Rawtherapee look at the bottom of the Detal block. Haze removal has just two parameters you can change: strength and distance. Depending on the kind of haze and conditions under which the photo was taken, it…

Our emoji match game is based on the traditional card game Snap. We’re presenting a number of shuffled emoji images from the computer, followed by an equal number of random emoji buttons for our player to click. Only one emoji in each deck will match. Paired with the score mechanics and the count-down timer, this makes for an invigorating game. We could, however, make our emoji game even more like the original Snap if we presented only one computer-generated emoji/ card at a time, and enabled the player to click their button if their top card/emoji matched it. We could then rotate the computer’s card/ emoji through a deck and give the player a specific time limit to call a match before the emoji/card moved on. To make things even…

Although the Go application uses a single data type of metric (Gauge) because it’s ideal for the information that’s sent to Prometheus, the software can accept many types of data. The list of supported data types for metrics is the following: Counter: This is a cumulative value that’s used for representing increasing counters. The value of a counter can stay the same, go up or be reset to zero, but can’t decrease. Counters are usually used for representing cumulative values such as number of requests served so far, total number of errors and so on. Gauge: This is a single numerical value that’s allowed to increase or decrease. Gauges are usually used for representing values that can go up or down such as number of requests and time durations. Histogram:…