Ubuntu Linux - Map Wacom to one screen when using multiple screens

Quick Know-how post. How to limit a Wacom tablet in Ubuntu Linux to one screen, if you are having multiple displays.

Keywords: Wacom, Ubuntu, Linux, multiple screens, multiple displays

We need to gather system information with xrandr and xinput. First we use xrandr to determine the display, where the tablet should be active. Run xrandr

I want to have it on the primary display, witch is in my case DP-4.

Next we need to list the devices using xinput | grep -i Wacom

For me, it's id 12 to 15. No we map the Wacom tablet to DP-4

Done 🙂

BIOS Update of the HP ZBook 15u G4 using Linux

(not entirely true, I needed a Windows Virtual machine)

I wanted to run a BIOS Update for my HP ZBook 15u G4. Unfortunately, HP provides updates only for Windows.
Linux users are used to such sorrow - but I will most probably stick back to other vendors in the future, where the Linux support is better.

Quick guide

I've extracted the folders and files and put them into this archive file (Updated 28.02.2018, here is the old file). Download it and extract it directly to you USB device. The folder Hewlett-Packard should be then in the root directory on your flash drive.

Reboot and select the Update options in your BIOS. It will reboot several times. Don't worry, grab a cup of coffee.

Files: [BIOS-P78_0115.tar.xz] [BIOS-P78_0103.tar.xz (old)]

My story: How I run the Update without a native Windows on the Laptop

I downloaded the BIOS update from the HP support page for the HP ZBook and installed it in a Windows-Virtual Machine on another computer. Here you can select the creation of a USB stick. So I've created a "recovery" USB stick and copied the BIOS image from the Hewlett-Packard\BIOS\Current folder on the USB stick to the Hewlett-Packard\BIOS\New folder.

Now I rebooted the laptop into the BIOS and selected Update BIOS. The system recognised the Update from the USB stick and could install it.
IMPORTANT: Plug in the power supply during BIOS update. The last thing you want is a power-down during a BIOS update!

Don't worry, during the Update process the laptop boots a few times and shows some weird behaviour. Just let him do. Grab a cup of coffee

So, although it is officially not supported, there is a way of how to update the BIOS on the Laptop.

Update [28.02.2018] - I updated the archive file to the current BIOS vP78_0115 from 01.02.2018. The old file is still available

Civilization Beyond Earth - Fix for Arch Linux

I love the Civilization series. One of my favourites is Beyond Earth, where luckily a Linux Version exists on Steam. Awesome! 🙂

Unfortunately under Arch Linux this doesn't work out of the box but needs some fixing. First of all you need to run steam-native, instead of steam. For debugging it's the best to run it in a terminal. If you start Civ Beyond Earth and end up with a similar error like

Then you need to install the lib32-intel-tbb lib from the AUR. I had to enable multilib and install gcc-multilib, but then it build and I could finally start Civilization Beyond Earth.

Civilization Beyond Earth - In game (just at the beginning)

Another victory for the good cause! 🙂

Raspberry Pi 3 and H.256

Some time ago I got annoyed by some movies encoded in h.256 are not running smoothly on the Kodi of my Raspberry Pi 3.

h.256 is a block-oriented quite new video compression algorithm, that is unfortunately not supported natively by the hardware decoder on the Raspberry Pi 3. So it has to be done in Software, and apparently the computational power of the Pi is too weak.

Surfing through some fora, I found some people claiming, that overclocking the Raspberry Pi should be the solution. So I decided to give it a try.

Overclocking goal

The goal was to bring the h.265 codec smoothly on the screen, using 1080p@30fps. Some people said, that overclocking the pi to 1300MHz should be enough. So that's where I have to go.

Only do overclocking, with an adequate cooling system! Since the Raspberry ships without any heat sink, I needed to buy one.

Cooling system

I've decided to go with a plain Aluminium heat sink, but monitor the temperature very closely with cputemp and gputemp, two tools that ship by default on the Raspbian and OpenELEC:

Works. During the whole overclocking procedure I was connected to the Raspberry via ssh to monitor the temperatures very closely. At least one readout every second, ready to intervene if something goes nasty.

The goal was to keep the temperature below 85 degrees (soft-limit) and immediately cancel the procedure after 90 degree (hard-limit). During the overclocking procedure I reached the hard-limit.


And here we go. Backup /flash/config.txt before editing, so that you can set it back to default, once you have finished.

There are plenty of examples on this page. You may need to figure out, witch one works for you.

There's also this amazing wiki page about overclocking, the risks and the pitfalls. I think that's the resource you should read before getting started.

The default clocking settings for a Raspberry Pi are commented out, thus if you are unsure about your current configuration, just comment it out, reboot and you'll have the stable plain configuration again.

In the end, I tries to get the system working with the following configuration

System was stable, but heating up a lot, up to more than 85 degrees. That's an important threshold, because at 85 degrees the Raspberry starts to protect itself from the heat death by throttling down the CPU. So in overall you'll have no benefit from overclocking, except a small boost in performance before it throttles you down to worse throughput, than with plain vanilla settings.


The poor Raspberry Pi got really hot during this procedure! 1300 MHz would be too much for a long-period. Also because it throttles itself down, I did not get any benefit from the overclocking procedure.

And although I pushed it to the limit with the available cooling system, I couldn't reach a smooth experience.

So I consider h.265 as not suitable for my Raspberry Pi. Well, seems that I have to encode it to something more Raspberry friendly 🙂

Still, it was a nice project!



Benchmarking tool - Flops

Flops is a nice tool for benchmarking floating point operations of a CPU.

Under Arch Linux i had some problems compiling it, because the static linking towards openmp was not working properly. I've made a fork, fixed the issue by removing the -static flag (and replaces -std=c++0x to -std=c++11) and a pull request in the hope, it will be included in the mainline soon.

The tool itself is quite nice to compare the throughput of FLOPS on a CPU. It measures it under perfect conditions so be aware that the everyday performance will be lower.

Still: Nice tool 🙂

OCaml interpreter - Adding history support

I need to learn OCaml for one of my computer science courses. Although I am more the procedural programmer type, I like some of the concepts of functional languages and am also using them on a daily basis.

Some of the concepts are quite handy and nice - list comprehension, filter and lambda functions. They can help you keep your code clean and state-less.

Although I like Haskell a lot, i dislike OCaml for several reasons. One of them is that the interpreter doesn't support curses-like history. Unless you use the very nice rlwrap tool (in Linux)

And finally you can scroll back up to your mistyped command.

SHA-1 is dead

SHA1, the old secure hashing algorithm is now broken in practice. See the Google Security blog post on the first SHA1 collision.

SHA1 was already theoretically broken 2005, when Prof. Xiaoyun Wang announced a differential attack. By 2010 the NIST decided to announce SHA-1 as deprecated.

SHA1 is still in use in BitTorrent and on some https sites. As far as I know, Chrome is currently the only Browser, who considers SHA-1 signed certificates as not secure. Firefox is about to phase it out as well and Edge wants to do this in mid of this year.

BitTorrent uses SHA-1 as well. Since we now have the first proven collisions, this could become interesting in lawsuits coming from the content industry ...

SHA-1 is proven broken and must not be used anymore.