Category Archives: linux

Your own little internet speed monitor

I wanted to monitor my ISP’s service over time and could not find any available simple tool for that. The usual system monitoring tools are usually displaying averages, not min/max values. So I used WD40 (speedtest-cli) and duct tape (cron) to make my own.

You need to have a cron daemon set up and speedtest-cli installed.

Then prepare an empty csv file with a header like this (don’t forget a trailing newline!) and store it in a path of your choice:

Server ID,Sponsor,Server Name,Timestamp,Distance,Ping,Download,Upload,Share,IP Address

Set up a cronjob at an interval of your choice (don’t be a dick) to run a speed test and log the results to the csv file:

@hourly speedtest --csv >> /home/user/path/to/speedtest.csv

If you have a fast connection you might spot slow test servers that would badly bias your results, so exclude them using the --exclude option if necessary.

That’s all, you get a nice log of internet ping, upload and download speeds, ready to be visualized in your software of choice (like the best spreadsheet software in existence). I will have to complain to my ISP for that drop since mid December for sure:

And now that I have written this, I realise that for plotting I could also just use a min/max function for a moving time window in Grafana I guess? The speedtests would still be triggered and provide nice bursts of usage. Anyone got pointers on how to do that?

DCP-L2530DW printer/scanner on Archlinux

Find your printers IP (make sure it is static, e. g. by setting it up accordingly in your router). Adjust the IP in the lines below.


Install brscan5 and xsane.
As root run: brsaneconfig5 -a name="DCP-L2530DW" model="DCP-L2530DW" ip=


Install cups.
As root run: lpadmin -p DCP-L2530DW-IPPeverywhere -E -v "ipp://" -m everywhere

And you are ready to go, enjoy!

Building QGIS with debugging symbols

As I keep searching the web for way too long again and again, I hope this post will be #1 next I forget how to build QGIS with debugging symbols.

Add CMAKE_BUILD_TYPE=Debug to the cmake invocation.


cmake -G "Unix Makefiles" ../ \

For a not as safe but more performant compilation, you can use RelWithDebInfo. I just found out today but will use that in the future rather than the full-blown Debug. See for some background.

On Archlinux, also add options=(debug !strip) in your PKGBUILD to have them not stripped away later.

Lots of CityGML files to a single obj to draco with localising coordinates to 0,0,0

I used the CityGML LoD2 model of Hamburg here, from (If you do this for Hamburg, you might want to not include Neuwerk’s tiles ;))


python2 -i -o LoD2-DE_HH_2017-12-31.zip_obj/

converts each CityGML file to a obj (takes about half an hour on my system).


mesh_cat LoD2-DE_HH_2017-12-31.zip_obj/*.obj -o

turns them into one single obj.

mesh_filter -center -scale 0.001 -rot 90 -1 0 0 LoD2-DE_HH_2017-12-31.zip_localised.obj

translates “so center of mass is at (0,0,0)” and scales to something smaller and rotates so that z is up. trimesh2’s documentation on the rot parameter is insufficient, I think my solution means “rotate by 90 degrees -1 times around x, 0 times around y, 0 times around z” or something like that. Look into the source if that helps you.


draco_encoder -i LoD2-DE_HH_2017-12-31.zip_localised.obj -o LoD2-DE_HH_2017-12-31.zip_localised.obj.drc

makes it tiny (8 Megabyte).

I did not do any error checking, used a epsilon of 1 in CityGML2OBJs and just wanted to play around.

Turn a Raspberry into a no-fancyshmancy mpd server with Archlinux ARM

Because my SD card keeps getting corrupted and I always start from scratch, here are my notes on how to turn a Raspberry Pi 2 with an always connected USB disk full of audio media into a nice little mpd server outputting via the 3.5mm jack. Probably works somewhat the same on a Raspberry Pi 3.

Install Archlinux ARM

And obviously update it right after, add your ssh key, whatever. Then:

Add packages to build a special mpd, sound stuff and common utils:
# pacman -Syu screen wget zip base-devel libmikmod unzip zziplib git doxygen boost alsa-utils hdparm ffmpeg htop libao audiofile libshout libmad faad2 libupnp libmms wavpack avahi libid3tag yajl libmpdclient

Get sound working

Add to /boot/config.cfg:

dtparam=audio=on  #
disable_audio_dither=1  # if you get white noise on low volume,
audio_pwm_mode=2  # better audio driver,

Make sure audio output is enabled, not muted, in # alsamixer.
# speaker-test -c6 -twav

Connect and mount external disk with all your media

Connect USB disk. Check UUID using ls -l /dev/disk/by-uuid/ or lsblk -f, add it to /etc/fstab at a mount point of your choice:
UUID=12341234-1234-1234-1234-123412341234 /media/egon ext4 defaults,nofail,x-systemd.device-timeout=1 0 2
and made sure that it can spin down by adding /etc/udev/rules.d/50-hdparm.rules (you might want to verify the hdparm call works first):
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="1", RUN+="/usr/bin/hdparm -B 1 -S 60 -M /dev/%k"
Then check if things work with # mount -a

Compile mpd with zip and curl support (optional, if not wanted, just install mpd from the repos)

I compiled my own mpd because I wanted zip support and Archlinux’s does not ship with that.
$ wget
$ tar xfvz mpd-git.tar.gz
$ cd mpd-git

Add ‘armv7h’ to the archs

and add some fancy configure options:

      --enable-zzip \
      --enable-mikmod \
      --enable-modplug \

$ makepkg
# pacman -U the resulting package

Takes about 30 minutes.

Configure mpd


user "mpd"
pid_file "/run/mpd/"
db_file "/var/lib/mpd/mpd.db"
state_file "/var/lib/mpd/mpdstate"
playlist_directory "/var/lib/mpd/playlists"
music_directory    "/media/egon"

audio_output {
  type            "alsa"
  name            "default"
  mixer_type      "software"      # optional

# systemctl enable mpd
# systemctl start mpd



Once it all works, make an image of it so that next time installation is just dd.

Initial setup failed. Cannot continue. Error: Couldn’t run mojosetup

If you are trying to install a game downloaded from but you get something like

$ ./
Verifying archive integrity… All good.
Uncompressing Shadow Tactics: Blades of the Shogun ( 100%
Collecting info for this system…
Operating system: linux
CPU Arch: x86_64
trying mojosetup in bin/linux/x86_64

Initial setup failed. Cannot continue.

Error: Couldn’t run mojosetup

then your file is corrupted or incomplete. You will have to re-download it. Ignore the “bin/linux/x86_64” path, that references something inside the installer, not something on your system.

Petition GOG to add checksums to their download pages or better yet, have reasonable download options that support resuming and HTTPS and what not…

One SRTMGL1 GeoTIFF to rule them all

NOTE: In up to date GDAL things might be easier AND I messed up with --config and -co below. Poke me to update it please.

So about half a year ago Lukas Martinelli asked about a global SRTM GeoTIFF. The SRTM elevation data is usually shared in many small tiles which can be ideal for some cases but annoying for others. I like downloading and processing big files so I took that as a challenge. It’s probably some mental thing. I never finished this blog post back then. It’s probably another mental thing. 8) Read on if you are interested in some GNU coreutils hackery as well as GDAL magick.

Here is how I did it. Endless thanks as usual to Even Rouault who fixed GDAL bugs and gave great hints. I learned more about GeoTIFFs and GDAL than I should have needed to know.

Downloading the source files

The source files are available at (warning, visiting this URL will make your browser cry and potentially render your system unresponsive). To download them you must create an NASA Earthdata Login at :\


                         U.S. GOVERNMENT COMPUTER

This US Government computer is for authorized users only.  By accessing this
system you are consenting to complete monitoring with no expectation of privacy.
Unauthorized access or use may subject you to disciplinary action and criminal

OMGOMGOMG. I am sure they would have used <blink> if accessibility guidelines allowed it. As I am not sure what their Terms of Service are, I will not give you a copy’n’paste ready line to download them all. wget or aria2 work well. You should get 14297 files with a total size of 98G.

Inspecting the ZIP files and preparing for GDAL’s vsizip

Each of those ZIP files has just a single file “.hgt” inside. GDAL specifically has support for the “SRTM HGT Format“, so we know it can read those files. We just need to extract them. (If you clicked that link you see that with GDAL 2.2 it will support directly loading the data from the ZIPs, that’s just Even being awesome.)

We don’t want to uncompress all those files just because we want to build a GeoTIFF from them later, do we? Luckily GDAL has a vsizip thingie which allows it to read files inside zip archives. Wicked! For this we need the “deep” paths to the files though, for example

The files inside the archives are always simply the same filename minus the “.SRTMGL1” and the .zip extension. Perfect, now we know all the files from inside the ZIPs! Right? Nope. Unfortunately some (17) of the archives do include the “.SRTMGL1” bit in their files, for example N38E051.SRTMGL1.hgt… >:(

That’s why we need to look into each zip file and determine the filename inside. (Alternatively *you* could extract them all after all, you with your fancy, huge SSD.)

We can simply use `unzip` with the `-t` switch to make it show what’s inside (and as a “free” benefit it will also check the file’s integrity for us). `tee` is used here to save the output to a file. This will take a while as it needs to read through all the files…

$ unzip -t "*" | tee unzip-t.log


testing: N29E000.hgt OK
No errors detected in compressed data of

testing: N27E033.hgt OK
No errors detected in compressed data of

testing: N45E066.hgt OK
No errors detected in compressed data of

14297 archives were successfully processed.
14297 archives were successfully processed.

Yay, no errors!

In the output we see the path to the archive and we see the name of the file inside. With some sed and grep we can easily construct “deep” paths.

First we remove the status lines, the blank lines and the very last full status line with `grep`:

$ cat unzip-t.log | grep -v -e "No errors" -e '^$' -e 'successfully processed'

testing: N12E044.hgt OK
testing: N29W002.hgt OK
testing: N45E116.hgt OK

Then we concatenate every consecutive two lines into one line with `paste` (I LOVE THIS 1 TRICK!):

$ cat unzip-t.log | grep -v -e "No errors" -e '^$' -e 'successfully processed' | paste - -

Archive: testing: N12E044.hgt OK
Archive: testing: N29W002.hgt OK
Archive: testing: N45E116.hgt OK

Finally we strip things away with sed (I don’t care that you would do it differently, this is how I quickly did it with my flair of hammering) and direct the output into a new file called `zips`:

$ cat unzip-t.log | grep -v -e "No errors" -e '^$' -e 'successfully processed' | paste - - | sed -e 's#Archive:[ ]*##' -e 's#\t[ ]*testing: #/#' -e 's#[ ]*OK##' > zips

Yay, we have all the actual inside-zip paths now!

If you are curious, you can try gdalinfo with those now. You need to prepend /vsizip/ to the path to make it read inside zip files.

$ gdalinfo /vsizip/

Driver: SRTMHGT/SRTMHGT File Format
Files: /vsizip/
Size is 3601, 3601
Coordinate System is:
        SPHEROID["WGS 84",6378137,298.257223563,
Origin = (43.999861111111109,13.000138888888889)
Pixel Size = (0.000277777777778,-0.000277777777778)
Corner Coordinates:
Upper Left  (  43.9998611,  13.0001389) ( 43d59'59.50"E, 13d 0' 0.50"N)
Lower Left  (  43.9998611,  11.9998611) ( 43d59'59.50"E, 11d59'59.50"N)
Upper Right (  45.0001389,  13.0001389) ( 45d 0' 0.50"E, 13d 0' 0.50"N)
Lower Right (  45.0001389,  11.9998611) ( 45d 0' 0.50"E, 11d59'59.50"N)
Center      (  44.5000000,  12.5000000) ( 44d30' 0.00"E, 12d30' 0.00"N)
Band 1 Block=3601x1 Type=Int16, ColorInterp=Undefined
  NoData Value=-32768
  Unit Type: m

Hooray! GDAL reads the hgt file from inside its zip!

We need to prepend all the paths with `/vsizip/` so let’s do that:

$ sed 's#^#/vsizip/##' zips > vsizips


Unfortunately those 17 misnamed files from earlier need special treatment… This is what my notes say, not sure what it was supposed to do. If you are recreating this all, please just ask me and I will look at it again. For now, let’s just pretend that this leads to a file called `hgtfiles` in which all the paths are perfect and all the files are perfect.

grep -v 'SRTMGL1.hgt$' vsizips > vsizipswithoutmisnamedfiles
mkdir misnamedfiles
cd misnamedfiles/
nano ../listofmisnamedfiles # insert the paths to those 17 zips here #TODO
while read filename; do unzip "../${filename}"; done < ../listofmisnamedfiles
rename 's/SRTMGL1.//' *.hgt
cd ..
find misnamedfiles/ -type f > listofmisnamedfileshgt
cat listofmisnamedfileshgt vsizipswithoutmisnamedfiles > hgtfiles

As I said above though, go with a recent GDAL and this is all much easier. Even even included a check for the different filenames inside, how can you not like that guy!

Building a Virtual Raster Table

Virtual Raster Tables (VRT) are some kind of files that pretend to be rasters. They are awesome. Here we use a VRT that simply turns all the small rasters we have into one big ass raster.

Ok, ready to create a Virtual Raster Table!

$ time gdalbuildvrt -input_file_list hgtfiles srtmgl1.003.vrt

0...10...20...30...40...50...60...70...80...90...100 - done.

real 0m22.679s
user 0m19.250s
sys 0m3.105s


You could go ahead and use this for your work/leisure now. But remember, it is tens of gigabytes of data so if you do not use it at a 1:1 scale things will not be fun and might fry your cat. You want overviews/pyramids.

Turning the VRT into a GeoTIFF (Optional)

Let’s make a HUGEGEOTIFF because that’s cool! You don’t have to, instead you could build overviews for the .vrt file.

We want it quick to read and small so I used DEFLATE, TILED and the horizontal predictor. I ran this on a weak i7 with 2G of RAM and can’t remember what the worst bottleneck was. Probably CPU.

$ time gdal_translate -co NUM_THREADS=ALL_CPUS --config PREDICTOR 2 -co COMPRESS=DEFLATE -co TILED=YES -co BIGTIFF=YES srtmgl1.003.vrt srtmgl1.003.vrt.tif

Input file size is 1296001, 417601
0...10...20...30...40...50...60...70...80...90...100 - done.

real 231m57.961s
user 503m23.044s
sys 3m14.600s

If you are courageous you can load that file in your GIS now. But again, unless you watch it at a 1:1 scale or something close to that it WILL not be much fun and potentially expose weaknesses in your GIS and fill up your system’s memory and crash and you had no unsaved work open, didn’t you?

Building Overviews

Overviews aka pyramids are usually about 1/3 the size of the full image. If they are not, you probably used different compression settings. This was the step that I expected to be just boring to wait for, but it turned out the most problematic. I tried all available free tools but none worked properly with an input this big. With GDAL we found a workaround after a while.

gdaladdo has problems building multiple overview levels with a file this big… The trick is to built the overviews sequentially, not in one invocation. The best solution at the moment was building overviews for overviews for overviews and so on until you reach a comfortable size. Something like:

gdaladdo -ro srtmgl1.003.tif 2
gdaladdo -ro srtmgl1.003.tif.ovr 2
gdaladdo -ro srtmgl1.003.tif.ovr.ovr 2
gdaladdo -ro srtmgl1.003.tif.ovr.ovr.ovr 2
gdaladdo -ro srtmgl1.003.tif.ovr.ovr.ovr.ovr 2 4 8 16 32 64 128 256 512

I used the following parameters:


Apparently gdaladdo automatically makes them tiled, which is good. I used to find out.

Creating overviews took just about 3 hours with this weird trick. So, in total the processing just takes half a day.


Enjoy! I impose no license/copyright/whatever on this derivative work.


Hillshading? Slope? You do it!

Found a better, faster way? You blog it!

We could add the overviews to the main image with `gdal_translate srtmgl1.003.tif srtmgl1.003.withovr.tif -co COPY_SRC_OVERVIEWS=YES [other options]` says Even.

e-foto (free GNU/GPL educational digital photogrammetric workstation) on Archlinux

I wrote this a year ago and meant to write more. Turns out I did not but it still works. You might need to figure out dependencies yourself. Here you go:

e-foto is a free GNU/GPL educational digital photogrammetric workstation in active development.

svn checkout e-foto-code
cd e-foto-code/c
tar xfv shapelib-1.3.0.tar.gz
mv shapelib-1.3.0 shapelib
cd ..
mkdir build
cd build
qmake-qt4 ../ 

Ready to run in


ffmpeg on raspbian / Raspberry Pi

Since is a bit messy, here is how you can compile ffmpeg with x264 on raspbian. Changes are building in your home directory, getting just a shallow git clone and building with all CPU cores. Also no unnecessary sudo…

Read the comments below!

# In a directory of your choosing (I used ~/ffmpeg):

# build and install x264
git clone --depth 1 git://
cd x264
./configure --host=arm-unknown-linux-gnueabi --enable-static --disable-opencl
make -j 4
sudo make install
# build and make ffmpeg
git clone --depth=1 git://
cd ffmpeg
./configure --arch=armel --target-os=linux --enable-gpl --enable-libx264 --enable-nonfree
make -j4
sudo make install

Read the comments below!

Hopefully someone, somewhere will provide a repository for this kind of stuff some day.

It takes just 25 minutes on a Raspberry Pi 3. Not hours or days like some old internet sources on old Raspis say.

In case you are wondering v4l2 should work with this.

Let’s Encrypt with Lighttpd

Save the page locally and use a clean browser to open the HTML file.
Create your keys and everything.
Cat domain.key and chained.pem into a new pemfile.
Grab the Let’s Encrypt Authority X1 (IdenTrust cross-signed) pemfile from
Put those two files in a safe place on your server.
Don’t forget to set proper permissions on the files. = "/path/to/lets-encrypt-x1-cross-signed.pem" # the Let's Encrypt certificate
ssl.pemfile = "/path/to/pemfile.pem" # your pemfile

Restart lighttpd.