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Fedora 29 on ARM on AWS

This week Amazon announced their new A1 arm64 EC2 Instances powered by their arm64 based Graviton Processors and, with a minor delay, the shiny new Fedora 29 for aarch64 (arm64) is now available to run there too!

Details on getting running on AWS is in this good article on using AWS tools on Fedora article and over all using Fedora on the AWS arm64 EC2 is the same as x86_64.

So while a new architecture on AWS is very exciting it’s at the same time old and boring! You’ll get the same versions of kernel, same features like SELinux and the same versions of the toolchain stacks, like the latest gcc, golang, rust etc in Fedora 29 just like all other architectures. You’ll also get all the usual container tools like podman, buildah, skopeo and kubernetes, and orchestration tools like ansible. Basically if you’re using Fedora on AWS you should be able use it in the same way on arm64.

Getting started

The initial launch of A1 aarch64 instances are available in the following four regions: US East (N. Virginia), US East (Ohio), US West (Oregon), Europe (Ireland). Direct links to launch the Fedora aarch64 AMIs directly are available here on the Fedora Cloud site.

Getting help

The Fedora support for aarch64 is very robust. It’s been widely used and tested across a number of platforms but of course with new users and new use cases will pick up issues that we’ve yet to encounter. So what is the best way to get help? If you’re having a crash in a particular application it should be reported in the usual way through RH Bugzilla, we have an ARMTracker tracker alias to block against to help identify Arm issues. For assistance with Arm specific queries and issues the Fedora Arm mailing list and we have the #fedora-arm IRC channel on Freenode.

Known issues

We have one known issue. The instance takes a while to get started, it can be up to 5 minutes. This is due to entropy and has been a general problem in virtual environments, across all architectures. We’re working to speed this up and it should be fixed soon. Once things are up an running though everything runs as expected.

Upcoming features

There will be Fedora 29 Atomic host coming in the next Two Week Atomic release, we unfortunately missed their release this time by a small window but it’ll be available in about 2 weeks with their next release and will appear on the site once released. We can’t let you have all the fun at once ūüėČ

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VS Code Live Share plugin

Contributing to Open Source projects leads to collaborating with people around the world this is traditionally done via emails or instant messages. But with the rise of extreme programing practices like pair programing being able to remotely share a code editor is a great feature. VS Code has a plugin Live Share that does just that.

Getting Started with Live Share

If you do not have VS Code already installed, you can read our previous article to get started.

Using Visual Studio Code on Fedora

Installing the Live Share plugin

First let’s install the dependencies the Live Share plugin requires.

$ sudo dnf install openssl-libs krb5-libs libicu zlib gnome-keyring libsecret desktop-file-utils xorg-x11-utils

Once the installation completes, the Live Share plugin is ready to be installed from the Extensions marketplace.

More details on the role of each dependency can be found in the Documentation.

Finally reload VS Code to activate the new plugin.

Start a Collaboration Session

To start a new collaboration session, it requires a project to be open in VS Code, so let’s clone the following git repository and open it.

$ git clone https://github.com/cverna/rss_feed_notifier.git

This repository contains the source code of the following Magazine article.

Never miss a Magazine article — build your own RSS notification system

In VS Code, use the [Ctrl+K, Ctrl+O] combination to select and open the git repository.

Then from the Live Share extension menu start a collaboration session.

Live Share requires its user to sign in so that it can display the identity of the session participants. You can easily sign in using a GitHub account for example.

Ready to collaborate

To start collaborating Live Share provides a link that can be shared with others. You can get this link in you clipboard by clicking on the Invite paticipants … text.

Once one or more participant have joined the session you can start collaborating.

Sharing Code

This is where Live Share really shines as it shows clearly which participant is currently editing the file.

It is also possible to follow a participant. This has for effect to open in your editor all the files that the participant you are following opens.

Sharing Resources

Another feature of Live Share is to share resources like a server, a terminal or even a debugger session. For example it is very easy to share a terminal session and help a participant setting up a development environment, another example would be to share a database server and to inspect the content of a table.

Connectivity

By default the Live Share connection automatically checks if the host machine and the guest machine can communicate directly, if not Live Share uses a relay hosted in the Azure cloud.

It is possible to configure Live Share to use only direct connection between the host and the guest. For that the host machine needs to open a port in the 5990-5999 range and accept inbound local network connections. The guest needs a network route and outbound access to the host on the same port.

Finally set the connection mode to direct in the Live Share settings.

The documentation provides more details on the connectivity options.

Please note that the Live Share extension is available as Public Preview. The extension source code is currently not open source but this should change once the extension is generally available.

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Design faster web pages, part 3: Font and CSS tweaks

Welcome back to this series of articles on designing faster web pages. Part 1 and part 2 of this series covered how to lose browser fat through optimizing and replacing images. This part looks at how to lose additional fat in CSS (Cascading Style Sheets) and fonts.

Tweaking CSS

First things first: let’s look at where the problem originates. CSS was once a huge step forward. You can use it to style several pages from a central style sheet. Nowadays, many web developers use frameworks like Bootstrap.

While these frameworks are certainly helpful, many people simply copy and paste the whole framework. Bootstrap is huge; the “minimal” version of 4.0 is currently 144.9 KB. Perhaps in the era of terabytes of data, this isn’t much. But as they say, even small cattle makes a mess.

Look back at the getfedora.org example. Recall in part 1, the first analysis showed the CSS files used nearly ten times more space than the HTML itself. Here’s a display of the stylesheets used:

That’s nine different stylesheets. Many styles in them that are also unused on the page.

Remove, merge, and compress/minify

The font-awesome CSS inhabits the extreme end of included, unused styles. There are only three glyphs of the font used on the page. To make that up in KB, the font-awesome CSS used at getfedora.org is originally 25.2 KB. After cleaning out all unused styles, it’s only 1.3 KB. This is only about 4% of its original size! For Bootstrap CSS, the difference is 118.3 KB original, and 13.2 KB after removing unused styles.

The next question is, must there be a bootstrap.css and a font-awesome.css? Or can they be combined? Yes, they can. That doesn’t save much file¬†space, but the browser now requests fewer files to succesfully render the page.

Finally, after merging the CSS files, try to remove unused styles and minify them. In this way, you save 10.1 KB for a final size of 4.3 KB.

Unfortunately, there’s no packaged “minifier” tool in Fedoras repositories yet. However, there are hundreds of online services to do that for you. Or you can use CSS-HTML-JS Minify, which is Python, and therefore easy to isntall. There’s not an available tool to purify CSS, but there are web services like UnCSS.

Font improvement

CSS3 came with something a lot of web developer like. They could define fonts the browser downloads in the background to render the page. Since then, a lot of web designers are very happy, especially after they discovered the usage of icon fonts for web design. Font sets like Font Awesome are quiet popular today and widely used. Here’s the size of that content:

current free version 912 glyphs/icons, smallest set ttf 30.9KB, woff 14.7KB, woff2 12.2KB, svg 107.2KB, eot 31.2

So the question is, do you need all the glyphs? In all¬†probability, no. You can get rid of them with FontForge, but that’s a lot of work. You could also use Fontello. Use the public instance, or set up your own, as it’s free software and available on Github.

The downside of such customized font sets is you must host the font by yourself. You can’t use other online font services to provide updates. But this may not really be a downside, compared to faster performance.

Conclusion

Now you’ve done everything you can to the content itself, to minimize what the browser loads and interprets. From now on, only tricks with the administration of the server can help.

One easy to do, but which many people do wrong, is decide on some intelligent caching. For instance, a CSS or picture file can be cached for a week. Whatever you do, if you use a proxy service like Cloudflare or build your own proxy, minimze the pages first. Users like fast loading pages. They’ll (silently) thank you for it, and the server will have a smaller load, too.

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Design faster web pages, part 2: Image replacement

Welcome back to this series on building faster web pages. The last article¬†talked about what you can achieve just through image compression. The example started with 1.2MB of browser fat, and reduced down to a weight of 488.9KB. That’s still not fast enough! This article continues the browser diet to lose more fat. You might think that partway through this process things are a bit crazy, but once finished, you’ll understand why.

Preparation

Once again this article starts with an analysis of the web pages. Use the built-in screenshot function of Firefox to make a screenshot of the entire page. You’ll also want to install Inkscape using sudo:

$ sudo dnf install inkscape

If you want to know how to use Inkscape, there are already several articles in Fedora Magazine. This article will only explain some basic tasks for optimizing an SVG for web use.

Analysis

Once again, this example uses the getfedora.org web page.

Getfedora page with graphics marked

Getfedora page with graphics marked

This analysis is better done graphically, which is why it starts with a screenshot. The screenshot above marks all graphical elements of the page. In two cases or better in four cases, the Fedora websites team already used measures to replace images. The icons for social media are glyphs from a font and the language selector is an SVG.

There are several options for replacing:

HTML5 Canvas

Briefly, HTML5 Canvas is an HTML element that allows you to draw with the help of scripts, mostly JavaScript, although it’s not widely used yet. As you draw with the help of scripts, the element can also be animated. Some examples of what you can achieve with HTML Canvas include this triangle pattern, animated wave, and¬†text animation. In this case, though, it seems not to be the right choice.

CSS3

With Cascading Style Sheets you can draw shapes and even animate them. CSS is often used for drawing elements like buttons. However, more complicated graphics via CSS are usually only seen in technical demonstration pages. This is because graphics are still better done visually as with coding.

Fonts

The usage of fonts for styling web pages is another way, and Fontawesome is quiet popular. For instance, you could replace the Flavor and the Spin icons with a font in this example. There is a negative side to using this method, which will be covered in the next part of this series, but it can be done easily.

SVG

This graphics format has existed for a long time and was always supposed to be used in the browser. For a long time not all browsers supported it, but that’s history. So the best way to replace pictures in this example is with SVG.

Optimizing SVG for the web

To optimize an SVG for internet use requires several steps.

SVG is an XML dialect. Components like circle, rectangle, or text paths are described with nodes. Each node is an XML element. To keep the code clean, an SVG should use as few nodes as possible.

The SVG example is a circular icon with a coffee mug on it. You have 3 options to describe it with SVG.

Circle element with the mug on top

<circle style="opacity:1;fill:#717d82;fill-opacity:1;stroke:none;stroke-width:9.51950836;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;paint-order:markers fill stroke" id="path36" cx="68.414307" cy="130.71523" r="3.7620001" />

Circular path with the mug on top

<path style="opacity:1;fill:#717d82;fill-opacity:1;stroke:none;stroke-width:1.60968435;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;paint-order:markers fill stroke" d="m 68.414044,126.95318 a 3.7618673,3.7618673 0 0 0 -3.76153,3.76204 3.7618673,3.7618673 0 0 0 3.76153,3.76205 3.7618673,3.7618673 0 0 0 3.76206,-3.76205 3.7618673,3.7618673 0 0 0 -3.76206,-3.76204 z" id="path20" />

single path

<path style="opacity:1;fill:#717d82;fill-opacity:1;stroke:none;stroke-width:1.60968435;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;paint-order:markers fill stroke" d="m 68.414044,126.95318 a 3.7618673,3.7618673 0 0 0 -3.76153,3.76204 3.7618673,3.7618673 0 0 0 3.76153,3.76205 3.7618673,3.7618673 0 0 0 3.76206,-3.76205 3.7618673,3.7618673 0 0 0 -3.76206,-3.76204 z m -1.21542,0.92656 h 2.40554 c 0.0913,0.21025 0.18256,0.42071 0.27387,0.63097 h 0.47284 v 0.60099 h -0.17984 l -0.1664,1.05989 h 0.24961 l -0.34779,1.96267 -0.21238,-0.003 -0.22326,1.41955 h -2.12492 l -0.22429,-1.41955 -0.22479,0.003 -0.34829,-1.96267 h 0.26304 l -0.16692,-1.05989 h -0.1669 v -0.60099 h 0.44752 c 0.0913,-0.21026 0.18206,-0.42072 0.27336,-0.63097 z m 0.12608,0.19068 c -0.0614,0.14155 -0.12351,0.28323 -0.185,0.42478 h 2.52336 c -0.0614,-0.14155 -0.12248,-0.28323 -0.18397,-0.42478 z m -0.65524,0.63097 v 0.21911 l 0.0594,5.2e-4 h 3.35844 l 0.0724,-5.2e-4 v -0.21911 z m 0.16846,0.41083 0.1669,1.05937 h 2.80603 l 0.16693,-1.05937 -1.57046,0.008 z m -0.061,1.25057 0.27956,1.5782 1.34411,-0.0145 1.34567,0.0145 0.28059,-1.5782 z m 1.62367,1.75441 -1.08519,0.0124 0.19325,1.2299 h 1.79835 l 0.19328,-1.2299 z" id="path2714" inkscape:connector-curvature="0" />

You probably can see the code becomes more complex and needs more characters to describe it. More characters in a file result, of course, in a larger size.

Node cleaning

If you open an example SVG in Inkscape and press F2, that activates the Node tool. You should see something like this:

Inkscape - Node tool activated

Inkscape – Node tool activated

There are 5 nodes that aren’t necessary in this example — the ones in the middle of the lines. To remove them, select them one by one with the activated Node tool and press the¬†Del key. After this, select the nodes which define this lines and make them corners again using the toolbar tool.

Inkscape - Node tool make node a corner

Inkscape – Node tool make node a corner

Without fixing the corners, handles are used that define the curve, which gets saved and will increase file size. You have to do this node cleaning by hand, as it can’t be effectively automated. Now you’re ready for the next stage.

Use the Save as function and choose Optimized svg. A dialogue window opens where you can select what to remove or keep.

Inkscape - Dialog window for save as optimized SVG

Inkscape – Dialog window for save as optimized SVG

Even the little SVG in this example got down from 3.2 KB to 920 bytes, less than a third of its original size.

Back to the getfedora page: The grey voronoi pattern used in the background of the main section, after our optimization from Part 1 of this series, is down to 164.1 KB versus the original 211.12 KB size.

The original SVG it was exported from is 1.9 MB in size. After these SVG optimization steps, it’s only 500.4KB. Too big? Well, the current blue background is 564.98 KB in size. But there’s only a small difference between the SVG and the PNG.

Compressed files

$ ls -lh insgesamt 928K -rw-r--r--. 1 user user 161K 19. Feb 19:44 grey-pattern.png -rw-rw-r--. 1 user user 160K 18. Feb 12:23 grey-pattern.png.gz -rw-r--r--. 1 user user 489K 19. Feb 19:43 greyscale-pattern-opti.svg -rw-rw-r--. 1 user user 112K 19. Feb 19:05 greyscale-pattern-opti.svg.gz

This is the output of a small test I did to visualize this topic. You should probably see that the raster graphic — the PNG — is already compressed and can’t be anymore. The opposite is the SVG, an XML file. This is just text and can compressed, to less then a fourth of its size. As a result it is now around 50 KB smaller in size than the PNG.

Modern browsers can handle compressed files natively. Therefore, a lot of web servers have switched on mod_deflate (Apache) and gzip¬†(nginx). That’s how we save space during delivery. Check out if it’s enabled at your server here.

Tooling for production

First of all, nobody wants to always optimize SVG in Inkscape. You can run Inkscape without a GUI in batch mode, but there’s no option to convert from Inkscape SVG to optimized SVG. You can only export raster graphics this way. But there are alternatives:

  • SVGO (which seems not actively developed)
  • Scour

This example will use scour for optimization. To install it:

$ sudo dnf install scour

To automatically optimize an SVG file, run scour similarly to this:

[user@localhost ]$ scour INPUT.svg OUTPUT.svg -p 3 --create-groups --renderer-workaround --strip-xml-prolog --remove-descriptive-elements --enable-comment-stripping --disable-embed-rasters --no-line-breaks --enable-id-stripping --shorten-ids

This is the end of part two, in which you learned how to replace raster images with SVG and how to optimize it for usage. Stay tuned to the Fedora Magazine for part three, coming soon.

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Design faster web pages, part 1: Image compression

Lots of web developers want to achieve fast loading web pages. As more page views come from mobile devices, making websites look better on smaller screens using responsive design is just one side of the coin. Browser Calories can make the difference in loading times, which satisfies not just the user but search engines that rank on loading speed. This article series covers how to slim down your web pages with tools Fedora offers.

Preparation

Before you sart to slim down your web pages, you need to identify the core issues. For this, you can use Browserdiet. It’s a browser add-on available for Firefox, Opera and Chrome and other browsers. It analyzes the performance values of the actual open web page, so you know where to start slimming down.

Next you’ll need some pages to work on. The example screenshot shows a test of¬†getfedora.org. At first it looks very simple and responsive.

Browser Diet - values of getfedora.org

Browser Diet – values of getfedora.org

However, BrowserDiet’s page analysis shows there are 1.8MB in files downloaded. Therefore, there’s some work to do!

Web optimization

There are over 281 KB of JavaScript files, 203 KB more in CSS files, and 1.2 MB in images. Start with the biggest issue — the images. The tool set you need for this is GIMP, ImageMagick, and optipng. You can easily install them using the following command:

sudo dnf install gimp imagemagick optipng

For example, take the following file which is 6.4 KB:

First, use the file command to get some basic information about this image:

$ file cinnamon.png cinnamon.png: PNG image data, 60 x 60, 8-bit/color RGBA, non-interlaced 

The image — which is only in grey and white — is saved in 8-bit/color RGBA mode. That’s not as efficient as it could be.

Start GIMP so you can set a more appropriate color mode. Open cinnamon.png in GIMP. Then go to Image>Mode and set it to greyscale. Export the image as PNG with compression factor 9. All other settings in the export dialog should be the default.

$ file cinnamon.png cinnamon.png: PNG image data, 60 x 60, 8-bit gray+alpha, non-interlaced 

The output shows the file’s now in 8bit gray+alpha mode. The file size has shrunk from 6.4 KB to 2.8 KB. That’s already only 43.75% of the original size. But there’s more you can do!

You can also use the ImageMagick tool identify to provide more information about the image.

$ identify cinnamon2.png cinnamon.png PNG 60x60 60x60+0+0 8-bit Grayscale Gray 2831B 0.000u 0:00.000

This tells you the file is 2831 bytes. Jump back into GIMP, and export the file. In the export dialog disable the storing of the time stamp and the alpha channel color values to reduce this a little more. Now the file output shows:

$ identify cinnamon.png cinnamon.png PNG 60x60 60x60+0+0 8-bit Grayscale Gray 2798B 0.000u 0:00.000

Next, use optipng to losslessly optimize your PNG images. There are other tools that do similar things, including advdef (which is part of advancecomp), pngquant and pngcrush.

Run optipng on your file. Note that this will replace your original:

$ optipng -o7 cinnamon.png ** Processing: cinnamon.png 60x60 pixels, 2x8 bits/pixel, grayscale+alpha Reducing image to 8 bits/pixel, grayscale Input IDAT size = 2720 bytes Input file size = 2812 bytes Trying: zc = 9 zm = 8 zs = 0 f = 0 IDAT size = 1922 zc = 9 zm = 8 zs = 1 f = 0 IDAT size = 1920 Selecting parameters: zc = 9 zm = 8 zs = 1 f = 0 IDAT size = 1920 Output IDAT size = 1920 bytes (800 bytes decrease) Output file size = 2012 bytes (800 bytes = 28.45% decrease)

The option -o7 is the slowest to process, but provides the best end results. You’ve knocked 800 more bytes off the file size, which is now 2012 bytes.

To resize all of the PNGs in a directory, use this command:

$ optipng -o7 -dir=<directory> *.png

The option -dir lets you give a target directory for the output. If this option is not used, optipng would overwrite the original images.

Choosing the right file format

When it comes to pictures for the usage in the internet, you have the choice between:

JPG-LS and JPG 2000 are not widely used. Only a few digital cameras support these formats, so they can be ignored. aPNG is an animated PNG, and not widely used either.

You could save a few bytes more through changing the compression rate or choosing another file format. The first option you can’t do in GIMP, as it’s already using the highest compression rate. As there are no alpha channels in the picture, you can choose JPG as file format instead. For now use the default value of 90% quality — you could change it down to 85%, but then alias effects become visible. This saves a few bytes more:

$ identify cinnamon.jpg cinnamon.jpg JPEG 60x60 60x60+0+0 8-bit sRGB 2676B 0.000u 0:00.000 

Alone this conversion to the right color space and choosing JPG as file format brought down the file size from 23 KB to 12.3 KB, a reduction of nearly 50%.

PNG vs. JPG: quality and compression rate

So what about the rest of the images? This method would work for all the other pictures, except the Fedora “flavor” logos and the logos for the four foundations. Those are presented on a white background.

One of the main differences between PNG and JPG is that JPG has no alpha channel. Therefore it can’t handle transparency. If you rework these images by using a JPG on a white background, you can reduce the file size from 40.7 KB to 28.3 KB.

Now there are four more images you can rework: the backgrounds. For the grey background, set the mode to greyscale again. With this bigger picture, the savings also is bigger. It shrinks from 216.2 KB to 51.0 KB — it’s now barely 25% of its original size. All in all, you’ve shrunk 481.1 KB down to 191.5 KB — only 39.8% of the starting size.

Quality vs. Quantity

Another difference between PNG and JPG is the quality. PNG is a lossless compressed raster graphics format. But JPG loses size through compression, and thus affects quality. That doesn’t mean you shouldn’t use JPG, though. But you have to find a balance between file size and quality.

Achievement

This is the end of Part 1. After following the techniques described above, here are the results:

You brought image size down to 488.9 KB versus 1.2MB at the start. That’s only about a third of the size, just through optimizing with optipng. This page can probably be made to load faster still. On the scale from snail to hypersonic, it’s not reached racing car speed yet!

Finally you can check the results in Google Insights, for example:

In the Mobile area the page gathered 10 points on scoring, but is still in the Medium sector. It looks totally different for the Desktop, which has gone from 62/100 to 91/100 and went up to Good. As mentioned before, this test isn’t the be all and end all. Consider scores such as these to help you go in the right direction. Keep in mind you’re optimizing for the user experience, and not for a search engine.

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How to turn on an LED with Fedora IoT

Do you enjoy running Fedora, containers, and have a Raspberry Pi? What about using all three together to play with LEDs? This article introduces Fedora IoT and shows you how to install a preview image on a Raspberry Pi. You’ll also learn how to interact with GPIO in order to light up an LED.

What is Fedora IoT?

Fedora IoT is one of the current Fedora Project objectives, with a plan to become a full Fedora Edition. The result will be a system that runs on ARM (aarch64 only at the moment) devices such as the Raspberry Pi, as well as on the x86_64 architecture.

Fedora IoT is based on OSTree, like Fedora Silverblue and the former Atomic Host.

Download and install Fedora IoT

The official Fedora IoT images are coming with the Fedora 29 release. However, in the meantime you can download a Fedora 28-based image for this experiment.

You have two options to install the system: either flash the SD card using a dd command, or use a fedora-arm-installer tool. The Fedora Wiki offers more information about setting up a physical device for IoT. Also, remember that you might need to resize the third partition.

Once you insert the SD card into the device, you’ll need to complete the installation by creating a user. This step requires either a serial connection, or a HDMI display with a keyboard to interact with the device.

When the system is installed and ready, the next step is to configure a network connection. Log in to the system with the user you have just created choose one of the following options:

  • If you need to configure your network manually, run a command similar to the following. Remember to use the right addresses for your network:
    $ nmcli connection add con-name cable ipv4.addresses \ 192.168.0.10/24 ipv4.gateway 192.168.0.1 \ connection.autoconnect true ipv4.dns "8.8.8.8,1.1.1.1" \ type ethernet ifname eth0 ipv4.method manual
  • If there’s a DHCP service on your network, run a command like this:
    $ nmcli con add type ethernet con-name cable ifname eth0

The GPIO interface in Fedora

Many tutorials about GPIO on Linux focus on a legacy GPIO sysfis interface. This interface is deprecated, and the upstream Linux kernel community plan to remove it completely, due to security and other issues.

The Fedora kernel is already compiled without this legacy interface, so there’s no /sys/class/gpio on the system. This tutorial uses a new character device /dev/gpiochipN provided by the upstream kernel. This is the current way of interacting with GPIO.

To interact with this new device, you need to use a library and a set of command line interface tools. The common command line tools such as echo or cat won’t work with this device.

You can install the CLI tools by installing the libgpiod-utils package. A corresponding Python library is provided by the python3-libgpiod package.

Creating a container with Podman

Podman is a container runtime with a command line interface similar to Docker. The big advantage of Podman is it doesn’t run any daemon in the background. That’s especially useful for devices with limited resources. Podman also allows you to start containerized services with systemd unit files. Plus, it has many additional features.

We’ll create a container in these two steps:

  1. Create a layered image containing the required packages.
  2. Create a new container starting from our image.

First, create a file Dockerfile with the content below. This tells podman to build an image based on the latest Fedora image available in the registry. Then it updates the system inside and installs some packages:

FROM fedora:latest RUN  dnf -y update RUN  dnf -y install libgpiod-utils python3-libgpiod

You have created a build recipe of a container image based on the latest Fedora with updates, plus packages to interact with GPIO.

Now, run the following command to build your base image:

$ sudo podman build --tag fedora:gpiobase -f ./Dockerfile

You have just created your custom image with all the bits in place. You can play with this base container images as many times as you want without installing the packages every time you run it.

Working with Podman

To verify the image is present, run the following command:

$ sudo podman images REPOSITORY                 TAG        IMAGE ID       CREATED          SIZE localhost/fedora           gpiobase   67a2b2b93b4b   10 minutes ago  488MB docker.io/library/fedora   latest     c18042d7fac6   2 days ago     300MB

Now, start the container and do some actual experiments. Containers are normally isolated and don’t have an access to the host system, including the GPIO interface. Therefore, you need to mount it inside while starting the container. To do this, use the –device¬†option in the following command:

$ sudo podman run -it --name gpioexperiment --device=/dev/gpiochip0 localhost/fedora:gpiobase /bin/bash

You are now inside the running container. Before you move on, here are some more container commands. For now, exit the container by typing exit or pressing Ctrl+D.

To list the the existing containers, including those not currently running, such as the one you just created, run:

$ sudo podman container ls -a CONTAINER ID   IMAGE             COMMAND     CREATED          STATUS                              PORTS   NAMES 64e661d5d4e8   localhost/fedora:gpiobase   /bin/bash 37 seconds ago Exited (0) Less than a second ago           gpioexperiment

To create a new container, run this command:

$ sudo podman run -it --name newexperiment --device=/dev/gpiochip0 localhost/fedora:gpiobase /bin/bash

Delete it with the following command:

$ sudo podman rm newexperiment

Turn on an LED

Now you can use the container you already created. If you exited from the container, start it again with this command:

$ sudo podman start -ia gpioexperiment

As already discussed, you can use the CLI tools provided by the libgpiod-utils package in Fedora. To list the available GPIO chips, run:

$ gpiodetect gpiochip0 [pinctrl-bcm2835] (54 lines)

To get the list of the lines exposed by a specific chip, run:

$ gpioinfo gpiochip0

Notice there’s no correlation between the number of physical pins and the number of lines printed by the previous command. What’s important is the BCM number, as shown on pinout.xyz. It is not advised to play with the lines that don’t have a corresponding BCM number.

Now, connect an LED to the physical pin 40, that is BCM 21. Remember: the shorter leg of the LED (the negative leg, called the cathode) must be connected to a GND pin of the Raspberry Pi with a 330 ohm resistor, and the long leg (the anode) to the physical pin 40.

To turn the LED on, run the following command. It will stay on until you press Ctrl+C:

$ gpioset --mode=wait gpiochip0 21=1

To light it up for a certain period of time, add the -b (run in the background) and -s NUM (how many seconds) parameters, as shown below. For example, to light the LED for 5 seconds, run:

$ gpioset -b -s 5 --mode=time gpiochip0 21=1

Another useful command is gpioget. It gets the status of a pin (high or low), and can be useful to detect buttons and switches.

Closeup of LED connection with GPIO

Conclusion

You can also play with LEDs using Python — there are some examples here. And you can also use the i2c devices inside the container as well. In addition, Podman is not strictly related to this Fedora edition. You can install it on any existing Fedora Edition, or try it on the two new OSTree-based systems in Fedora: Fedora Silverblue and Fedora CoreOS.

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How to use VS Code for your Python projects

Visual Studio Code, or VS Code, is an open source code editor that also includes tools for building and debugging an application. With the Python extension enabled, vscode becomes a great working environment for any Python developer. This article shows you which extensions are useful, and how to configure VS Code to get the most out of it.

If you don’t have it¬†installed, check out our previous article, Using Visual Studio Code on Fedora:

Using Visual Studio Code on Fedora

Install the VS Code Python extension

First, to make VS Code Python friendly, install the Python extension from the marketplace.

Once the Python extension installed, you can now configure the Python extension.

VS Code manages its configuration inside JSON files. Two files are used:

  • One for the global settings that applies to all projects
  • One for project specific settings

Press Ctrl+, (comma) to open the global settings.

Setup the Python Path

You can configure VS Code to automatically select the best Python interpreter for each of your projects. To do this, configure the python.pythonPath key in the global settings.

// Place your settings in this file to overwrite default and user settings. { "python.pythonPath":"${workspaceRoot}/.venv/bin/python", }

This sets VS Code to use the Python interpreter located in the project root directory under the .venv virtual environment directory.

Use environment variables

By default, VS Code uses environment variables defined in the project root directory in a .env file. This is useful to set environment variables like:

PYTHONWARNINGS="once"

That setting ensures that warnings are displayed when your program is running.

To change this default, set the python.envFile configuration key as follows:

"python.envFile": "${workspaceFolder}/.env",

Code Linting

The Python extension also supports different code linters (pep8, flake8, pylint). To enable your favorite linter, or the one used by the project you’re working on, you need to set a few configuration items.

By default pylint is enabled. But for this example, configure flake8:

"python.linting.pylintEnabled": false, "python.linting.flake8Path": "${workspaceRoot}/.venv/bin/flake8", "python.linting.flake8Enabled": true, "python.linting.flake8Args": ["--max-line-length=90"],

After enabling the linter, your code is underlined to show where it doesn’t meet criteria enforced by the linter. Note that for this example to work, you need to install flake8 in the virtual environment of the project.

Code Formatting

VS Code also lets you configure automatic code formatting. The extension currently supports autopep8, black and yapf. Here’s how to configure black.

"python.formatting.provider": "black", "python.formatting.blackPath": "${workspaceRoot}/.venv/bin/black" "python.formatting.blackArgs": ["--line-length=90"], "editor.formatOnSave": true,

If you don’t want the editor to format your file on save,¬† set the option to false and use Ctrl+Shift+I to format the current document. Note that for this example to work, you need to install black in the virtual environment of the project.

Running Tasks

Another great feature of VS Code is that it can run tasks. These tasks are also defined in a JSON file saved in the project root directory.

Run a development flask server

In this example, you’ll create a task to run a Flask development server. Create a new Build using the basic template that can run an external command:

Edit the tasks.json file as follows to create a new task that runs the Flask development server:

{ // See https://go.microsoft.com/fwlink/?LinkId=733558 // for the documentation about the tasks.json format "version": "2.0.0", "tasks": [ { "label": "Run Debug Server", "type": "shell", "command": "${workspaceRoot}/.venv/bin/flask run -h 0.0.0.0 -p 5000", "group": { "kind": "build", "isDefault": true } } ] }

The Flask development server uses an environment variable to get the entrypoint of the application. Use the .env file to declare these variables. For example:

FLASK_APP=wsgi.py FLASK_DEBUG=True

Now you can execute the task using Ctrl+Shift+B.

Unit tests

VS Code also has the unit test runners pytest, unittest, and nosetest integrated out of the box. After you enable a test runner, VS Code discovers the unit tests and letsyou to run them individually, by test suite, or simply all the tests.

For example, to enable pytest:

"python.unitTest.pyTestEnabled": true, "python.unitTest.pyTestPath": "${workspaceRoot}/.venv/bin/pytest",

Note that for this example to work, you need to install pytest in the virtual environment of the project.

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Learn how to build your own Twitter bot with Python

Twitter allows one to share blog posts and articles with the world. Using Python and the tweepy library makes it easy to create a Twitter bot that takes care of all the tweeting for you. This article shows you how to build such a bot. Hopefully you can take the concepts here and apply them to other projects that use online services.

Getting started

To create a Twitter bot the tweepy library comes handy. It manages the Twitter API calls and provides a simple interface.

The following commands use Pipenv to install tweepy into a virtual environment. If you don’t have Pipenv installed, check out our previous article,¬†How to install Pipenv on Fedora.

$ mkdir twitterbot $ cd twitterbot $ pipenv --three $ pipenv install tweepy $ pipenv shell

Tweepy – Getting started

To use the Twitter API the bot needs to authenticate against Twitter. For that, tweepy uses the OAuth authentication standard. You can get credentials by creating a new application at https://apps.twitter.com/.

Create a new Twitter application

After you fill in the following form and click on the Create your Twitter application button, you have access to the application credentials. Tweepy requires the Consumer Key (API Key) and the Consumer Secret (API Secret), both available from the Keys and Access Tokens.

After scrolling down the page, generate an Access Token and an Access Token Secret using the Create my access token button.

Using Tweepy – print your timeline

Now that you have all the credentials needed, open a new file and write the following Python code.

import tweepy auth = tweepy.OAuthHandler("your_consumer_key", "your_consumer_key_secret") auth.set_access_token("your_access_token", "your_access_token_secret") api = tweepy.API(auth) public_tweets = api.home_timeline() for tweet in public_tweets: print(tweet.text)

After making sure that you are using the Pipenv virtual environment, run your program.

$ python tweet.py

The above program calls the home_timeline API method to retrieve the 20 most recent tweets from your timeline. Now that the bot is able to use tweepy  to get data from Twitter, try changing the code to send a tweet.

Using Tweepy – send a tweet

To send a tweet, the API method update_status comes in handy. The usage is simple:

api.update_status("The awesome text you would like to tweet")

The tweepy library has many other methods that can be useful for a Twitter bot. For the full details of the API, check the documentation.

A magazine bot

Let’s create a bot that searches for Fedora Magazine tweets and automatically retweets them.

To avoid retweeting the same tweet multiple times, the bot stores the tweet ID of the last retweet. Two helper functions, store_last_id and get_last_id, will be used to save and retrieve this ID.

Then the bot uses the tweepy search API to find the Fedora Magazine tweets that are more recent than the stored ID.

import tweepy def store_last_id(tweet_id): """ Store a tweet id in a file """ with open("lastid", "w") as fp: fp.write(str(tweet_id)) def get_last_id(): """ Read the last retweeted id from a file """ with open("lastid", "r") as fp: return fp.read() if __name__ == '__main__': auth = tweepy.OAuthHandler("your_consumer_key", "your_consumer_key_secret") auth.set_access_token("your_access_token", "your_access_token_secret") api = tweepy.API(auth) try: last_id = get_last_id() except FileNotFoundError: print("No retweet yet") last_id = None for tweet in tweepy.Cursor(api.search, q="fedoramagazine.org", since_id=last_id).items(): if tweet.user.name == 'Fedora Project': store_last_id(tweet.id) tweet.retweet() print(f'"{tweet.text}" was retweeted'

In order to retweet only tweets from the Fedora Magazine, the bot searches for tweets that contain fedoramagazine.org¬†and are published by the “Fedora Project” Twitter account.

Conclusion

In this article you saw how  to create a Twitter application using the tweepy Python library to automate reading, sending and searching tweets. You can now use your creativity to create a Twitter bot of your own.

The source code of the example in this article is available on Github.

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Anaconda improvements in Fedora 28

Fedora 28 was released last month, and the major update brought with it a raft of new features for the Fedora Installer (Anaconda).¬† Like Fedora, Anaconda is a dynamic software project with new features and updates every release. Some changes are user visible, while others happen under the hood — making Anaconda more robust and prepared for future improvements.

User & Root configuration on Fedora Workstation

When installing Fedora Workstation from the Live media, the user and root configuration screens are no longer in the installer. Setting up users is now only done in the Initial Setup screens after installation.

The progress hub on a Fedora 28 Workstation live installation.

The progress hub on a Fedora 28 Workstation live installation.

The back story is that the Fedora Workstation working group aimed to reduce the number of screens users see during installation.  Primarily, this included screens that let a user set option twice: both Anaconda and the Gnome Initial Setup tool upon first boot. The working group considered various options, such as Anaconda reporting which screens have been visited by the user and then hiding them in Gnome Initial Setup. In the end they opted for just always skipping the user and root configuration screens in Anaconda and just configuring a user with sudo rights in Gnome Initial Setup.

Because of this the respective screen (user creation) shows up just once (in Gnome Initial Setup), making the installation experience more consistent.

It’s also worth noting that this change only affects the Fedora Workstation live image. All other images, including the Fedora Workstation netinst image and other live images, are unaffected.

Anaconda on DBus

Last year we announced the commencement of our next major initiative — modularizing Anaconda. The main idea is to split the code into several modules that will communicate over DBus. This will provide better stability, extensibility and testability of Anaconda.

Fedora 28 is the first release where Anaconda operates via DBus. At startup, Anaconda starts its private message bus and ten simple modules. For now, the modules just hold data that are provided by a kickstart file and modified by the UI. The UI uses the data to drive installation. This means that you can use DBus to monitor current settings, but you should use the UI to change them.

You can easily explore the current Anaconda DBus API with the live version of Fedora Workstation 28. Just keep in mind that the API is still unstable, so it might change in the future.

To do so, boot the live image and install the D-Feet application:

sudo dnf install d-feet

Start the installer and get an address of the Anaconda message bus:

cat /var/run/anaconda/bus.address

Start D-Feet, choose the option ‚ÄėConnect to other Bus‚Äô and copy the first part of the Anaconda bus address to the text field (see the picture below). Click on the ‚ÄėConnect‚Äô button. The application will open a new tab and show you a list of available DBus services. Now you can view the interfaces, methods, signals and properties of Anaconda DBus modules and interact with them.

Connecting to the Anaconda DBUS session.

Connecting to the Anaconda DBUS session.

The Anaconda DBUS API as visible in D-Feet.

The Anaconda DBUS API as visible in D-Feet.

Blivet 3.0 and Pykickstart 3.0

Fedora 28 provides version 3 of blivet and Pykickstart, and Anaconda uses the updated versions too.  While this is not really visible from end user perspective, changes like this are important to assure a robust and maintainable future for the Anaconda installer.

The main change in Pykickstart 3 is the switch from the deprecated optparse module to argparse for kickstart parsing. This not only brings all the features argparse has, it was also one of the prerequisites for having automatically generated kickstart documentation on Read the Docs.

Blivet 3 is less radical  update, but includes significant API improvements and cleanups. Some installer-related code still sitting in Blivet was finally moved to Anaconda.

Migrating from authconfig to authselect

The authconfig tool is deprecated and replaced with authselect in Fedora 28, so Anaconda deprecated the kickstart command authconfig and introduced a new command: authselect. You can still use the authconfig command, but Anaconda will install and run the authselect-compat tool instead.

Enabled hibernation

Previously, Hibernation didn‚Äôt work after installation because of a missing kernel option, so it had to be set up manually. Starting with Fedora 28, Anaconda adds the kernel option ‚Äėresume‚Äô with a path to the largest available swap device by default on x86 architectures.

Reducing Initial Setup dependencies

The Initial Setup tool is basically a lightweight launcher for arbitrary configuration screens from Anaconda. And while Anaconda often runs from a dedicated installation image, Initial Setup always runs directly on the installed system. This also means all the dependencies of Initial Setup will end up on users system, and unless they are uninstalled, they will take up space more or less forever.

The situation is even more dire on ARM, where users generally just dd a Fedora image to memory card or internal storage on the ARM board and Initial Setup basically acts as the installer, customizing the otherwise identical image for the given user. In this case Initial Setup dependencies directly dictate how small the Fedora image can be.

In Fedora 28, the new anaconda-install-env-deps metapackage  depends on all installation-time-only dependencies. The anaconda-install-env-deps package is always installed on installation images (netinst, live), but is not an Initial Setup dependency and should thus prevent all the unnecessary packages from being pulled in to the installed system. There is also a nice side effect of finally consolidating all the install-time-only dependencies in the Anaconda spec file.

 

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Download an OS with GNOME Boxes

Boxes is the GNOME application for running virtual machines. Recently Boxes added a new feature that makes it easier to run different Linux distributions. You can now automatically install these distros in Boxes, as well as operating systems like FreeBSD and FreeDOS. The list even includes Red Hat Enterprise Linux. The Red Hat Developer Program includes a no-cost subscription to Red Hat Enterprise Linux. With a Red Hat Developer account, Boxes can automatically set up a RHEL virtual machine entitled to the Developer Suite subscription. Here’s how it works.

 

Red Hat Enterprise Linux

To create a Red Hat Enterprise Linux virtual machine, launch Boxes and click New. Select Download an OS from the source selection list. At the top, pick Red Hat Enterprise Linux. This opens a web form at developers.redhat.com. Sign in with an existing Red Hat Developer Account, or create a new one.

If this is a new account, Boxes requires some additional information before continuing. This step is required to enable the Developer Subscription on the account. Be sure to accept the Terms & Conditions now too. This saves a step later during registration.

 

Click Submit and the installation disk image starts to download. The download can take a while, depending on your Internet connection. This is a great time to go fix a cup of tea or coffee!

Once the media has downloaded (conveniently to ~/Downloads), Boxes offers to perform an Express Install. Fill in the account and password information and click Continue. Click Create after you verify the virtual machine details. The Express Install  automatically performs the entire installation! (Now is a great time to enjoy a second cup of tea or coffee, if so inclined.)

Once the installation is done, the virtual machine reboots and logs directly into the desktop. Inside the virtual machine, launch the Red Hat Subscription Manager via the Applications menu, under System Tools. Enter the root password to launch the utility.

Click the Register button and follow the steps through the registration assistant. Log in with your Red Hat Developers account when prompted.

Now you can download and install updates through any normal update method, such as yum or GNOME Software.

FreeDOS anyone?

Boxes can install a lot more than just Red Hat Enterprise Linux, too. As a front end to KVM and qemu, Boxes supports a wide variety of operating systems. Using libosinfo, Boxes can automatically download (and in some cases, install) quite a few different ones.

To install an OS from the list, select it and finish creating the new virtual machine. Some OSes, like FreeDOS, do not support an Express Install. In those cases the virtual machine boots from the installation media. You can then manually install.

Popular operating systems on Boxes

These are just a few of the popular choices available in Boxes today.

Ubuntu 17.10

Pop!_OS 17.10

EndlessOS 3

Fedora 28

openSUSE Tumbleweed

Debian 9

Fedora updates its osinfo-db package regularly. Be sure to check back frequently for new OS options.