System Maintenance Today, Downtime

I take the somewhat unusual approach, Of hosting this Web-site, and therefore also my blog, on my personal computer at home. Therefore, any downtime of my home computer, also affects the visibility of the blog. And, as long as the actual Web-server is not online, I also cannot make it display a maintenance-mode page.

Just in recent days, I took the more-unusual step, of running the command:

 


root@Phoenix:/home/dirk# update-initramfs -u -k 3.18.0-14-generic

 

What was unusual about this, was the fact that this was not the command:

 


root@Phoenix:/home/dirk# update-initramfs -u -k 3.16.0-4-amd64

 

While it seemed nice for some time, to be running a kernel-version named ‘3.18.0-14-generic’, the mainstream version which a Debian / Jessie system is supposed to be running, is ‘3.16.0-4-amd64′. So, while the mainstream kernel had been receiving regular updates, I was running a kernel, which had not been receiving any updates, for years now. This helped reduce the number of reboots which I needed to carry out, due to frequent updates on the ‘3.16.0’ kernel.

But just because this was the first time in ages, that I had run the ‘update-initramfs’ command on the running kernel, I next needed to attempt a reboot, just to see whether the computer could still boot.

Therefore, readers would have experienced problems accessing my blog or site, from about 16h40 until about 17h10 today.

And No, My system Failed to Reboot.

Continue reading System Maintenance Today, Downtime

How SDL Accelerates Video Output under Linux.

What we might know about the Linux, X-server, is that it offers pure X-protocol to render such features efficiently to the display, as Text with Fonts, Simple GUI-elements, and small Bitmaps such as Icons… But then, when it’s needed to send moving pictures to the display, we need extensions, which serious Linux-users take for granted. One such extension is the Shared-Memory extension.

Its premise is that the X-server shares a region of RAM with the client application, into which the client-application can draw pixels, which the X-server then transfers to Graphics Memory.

For moving pictures, this offers one way in which they can also be ~accelerated~, because that memory-region stays mapped, even when the client-application redraws it many times.

But this extension does not make significant use of the GPU, only of the CPU.

And so there exists something called SDL, which stands for Simple Direct Media Layer. And one valid question we may ask ourselves about this protocol, is how it achieves a speed improvement, if it’s only installed on Linux systems as a set of user-space libraries, not drivers.

(Updated 10/06/2017 : )

Continue reading How SDL Accelerates Video Output under Linux.

The Sort Of Software that will Not Run, on my Linux Tablet

In this posting I wrote, that I had installed Linux in a chroot-environment, on my old Samsung Galaxy Tab S, First Generation tablet, which remains an Android-based tablet. I did this specifically using the apps from the Google play store, named ‘GNURoot’ and ‘XSDL’, which do not require root.

Here, I gave a compendium of Linux-applications which do run in the resulting Linux guest-system.

I think that I need to point out a broad category of Linux applications that will always remain poor choices:

  • Audio Editors,
  • Video Editors.

The problem with any Audio Editor, is that it will eventually need to input and output Audio – not just edit sound files – and any Video Editor, needs to give a preview of all its video-clips – not just edit video files. This seems like a silly thing to write, but is non-trivial in my present context.

I have taken a Linux engine – GNURoot – and connected it to an externally-supplied X-server emulation – XSDL. The pipeline between these two Android apps is very narrow. It consists of X-server protocol – which is excellent and rendering text and GUIs, of shared memory at its maximum, and of a PulseAudio server, visible on the Linux side as such, but collectively running on the Android side as an SDL client.

I have no way to provide OpenGL or SDL on the Linux-side. What this means, is that virtually any non-linear video editor will want to see both installed on the Linux side, while neither is provided.

Continue reading The Sort Of Software that will Not Run, on my Linux Tablet