Building my own Recovery ROM for a Samsung J5 2017 (j5y17lte, TWRP)

| May 18, 2020
After several hours of sideloading a custom ROM and flashing a TWRP recovery image i thought the next step is to build a TWRP recovery image on my own.

So how to do that?

My startpoint was
(just search github for your device with TWRP)

But this is not the way to begin.
First you have to follow this page:
and do
repo init -u  (more...)

Samsung J5 2017 (aka j5y17lte) installing STOCK ROM

| May 16, 2020
After installing a custom ROM (s. here) i wanted to flash the STOCK  ROM onto my smartphone again.
So what to do?

First: Download a ROM (e.g.

and you will get something like
this zip cannot be sideloaded. So you have to unzip and the you have:
Within this you have to do a:

Corona-Homeoffice: second monitor for my laptop – portable!

| May 9, 2020
After several weeks working in homeoffice and my children in homeschooling i had to increase my efficieny. And the best thing is to get a second monitor running which meets the following requirements:
  • Single Plug (for signal and power)
  • Easy movable from living room to workspace and back
  • Touchscreen would be nice
 So i decided to buy a wimaxit 15.6" portable monitor and today it arrived:

The second screen is only connected (and (more...)

My Samsung Galaxy J5 (2017) aka j5y17lte with lineage os

| May 2, 2020
In the last weeks i did some tests with installing custom ROMs to my old devices:
The next step was to try this with my Samsung J5:
root@zerberus:~/bin# ./heimdall print-pit
Heimdall v1.4.2

Copyright (c) 2010-2017 Benjamin Dobell, Glass Echidna

This software is provided free of charge. Copying and redistribution is

If you appreciate this software and you (more...)

GPay and TWRP: NFC payment not possible / forbidden

| Apr 24, 2020
After flashing my old Samsung smartphone to TWRP (s. this posting) and before installing a custom OS, i did some tests with the original Android OS.
Everything worked but GPay refuses to work:

Your Phone can't make contactless payments
Check your phone software to see if it meets standards
Check software"
and the button "Check software" opens this popup:

Your phone doesn't meet software standards

You can't make contactless payments with this device. It (more...)

My Nexus 7 (2012) is online again (with lineageos and external battery)

| Apr 16, 2020
In 2014 i did the last update for my Nexus 7 (s. here).
It was the last update which was provided by Google for this device:

Using a video capture usb stick with Linux / Ubuntu

| Apr 7, 2020
Three weeks ago i ordered a video capture usb stick at banggood and today it arrived:

So will this device work with my ubuntu?

I inserted the stick on my laptop and dmesg showed:

[123483.143071] hid-generic 0003:534D:0021.0002: hiddev0,hidraw1: USB HID v1.10 Device [MACROSILICON AV TO USB2.0] on usb-0000:00:14.0-1/input4

That was all...
But there was a module missing:

modprobe uvcvideo
and after that:
[125822.751366] usb 1-1: new high-speed USB device  (more...)

Smartphone: Installing lineageOS + Googles Play Store (and getting 9GB system space freed up)

| Apr 4, 2020

After installing TWRP as bootloader i was wondering, how much effort is is to install an alternative to android on my old smartphone.

Heimdall & ADB were in place (see TWRP posting) - so let's start!

I downloaded the appropriate image from and i did the following on my smartphone:
Click on "Wipe"
 Click on "Format Data"
 Type "Yes"
 Step two times back and click "advanced wipe"
Choose "Cache" and (more...)

Using a custom bootloader for my smartphone: TWRP on Samsung Galaxy A3

| Apr 3, 2020
I read about /e/ some days ago and i decided to install this on my old smartphone (a samsung A3).

So first: What is /e/?
So i started at
where i learned, that i have to install a custom bootloader on my smartphone. This is very good explained at /e/:

(You will find there the description how to install "heimdall" and "adb")

schroff@zerberus:~/bin$ sudo ./heimdall flash --verbose --RECOVERY ~/Downloads/twrp-3. (more...)

Ubuntu: Disable screenlock after resuming from hibernation

| Mar 18, 2020
There are many tutorials out there, how to disable the screen locking.

The problem with these solutions is, that still after resuming from hibernation / standby the screenlock is triggered.

To disable this behaviour you can check this:
schroff@zerberus:~/$ gsettings get org.gnome.desktop.screensaver ubuntu-lock-on-suspend
and then do:

gsettings set org. (more...)

Streaming a live-stream… [ffmpeg + vlc for m3u8]

| Mar 15, 2020
After writing about how to stream a file to some smartphones or tablets, now the commands for streaming a live-stream to other devices.

And like before: VLC is needed.

But in addition to vlc you have to use ffmpeg:
A complete, cross-platform solution to record, convert and stream audio and video.

First thing you need is the url of the live-stream you want to re-stream. In my case is took the "Zweites Deutsches Fernsehen" (more...)

Streaming a video file with vlc to other devices (like smartphones, etc.)

| Mar 15, 2020
If you want to look a video on a tablet or smartphone (or laptop) and the file is on a server in your network, you can do this very easily with vlc.
One big advantage: The video can be consumed by many devices - so the movie can be watched on e.g. 3 tablets...

What do you have to do?
Install vlc on your computer (i used a ubuntu laptop) and start vlc.
Next (more...)

Squid: How to setup a proxy…

| Mar 14, 2020

If you are limited on bandwidth and you want to setup several machines, using a caching proxy will speed up your installation process significantly.

What is a caching proxy:

But proxies have some issues, that you should be aware of:

If you are sure, to use a proxy, just enter these commands:

root@zerberus:~# apt install squid
Reading package lists... Done
Building dependency tree      
Reading state information... Done
The following (more...)

Review: Blockchain for dummies

| Feb 21, 2020
The book "blockchain for dummies" provided by IBM contains 6 chapters on 41 pages. (Download from IBM)

The chapters 1 & 2 describe the basic of blockchain technology.
From my point of view, this part is a bit too shallow, because there is no single formular inside this book ;-)
But there are some nice illustrations given:

and the differences between a public blockchain and corporate blockchains are good explained including their  consequences.

Chapter (more...)

Oracle BPEL: What’s up with it?

| Jan 31, 2020
Nearly 20 years ago there was a new standard for modelling business processes: BPEL (
Oracle bought Collaxa and released the Oracle BPEL Process Manager.
In 2009 i wrote some posts over tutorials, which where from collaxa and which were very useful for starting with Oracle BPEL product:

And what is left today?

The product is still listed on Oracle homepage:

And there is a section (more...)

Oracle VM Server: OVMAPI_2005E and OVMEVT_003503D_000

| Jan 25, 2020
In my OVM environment i was trying to delete a server from a pool and this did not work. The error i got signalled was:
OVMAPI_2005E "[ServerDbImpl] xx:yy:zz:... (oraclevm)" contains a component "xx:yy:zz:..." in error. Error event: server.cluster.failure., Summary: Server Cluster Failure, Description: Failed to leave cluster OVMEVT_003503D_000 Server reboot is required..
I rebootet the server: still the same error.
I rebootet the ovm manager: still the same error.

Then i (more...)

Oracle VM Server: Pool is locked forever

| Dec 23, 2019
If you are using Oracle VM Server it is possible that you are hitting the following problem:

After changing something on a server pool the pool gets locked and the lock stays there:
Even a reboot of your OVMM (oracle vm manager) does not remove the lock.

The solution can be very easy:
Just edit the pool and add (or change) the description.

This edit triggers an update and removes the lock. I think every (more...)

Microsofts Visual Studio Code on Linux

| Dec 10, 2019
On the last weekend i was wondering, what kind of IDE i can use for doing some small programs with javascript. My first idea was eclipse, but a friend mentioned Microsofts Visual Studio Code:
 So i opened and got
So i downloaded the .deb and after a dpkg -i of that file i was able to run Visual Studio Code on my Linux machine:
schroff@zerberus:~$ code 
The startup was amazing fast - (more...)

Linux ser2net: no connection to /dev/ttyUSB0

| Dec 1, 2019
If you are running some java application on a Linux box (especially ARM architecture) and this application accesses the serial interface (/dev/ttyUSB0, /dev/ttyUSB1 or just /dev/ttyX), then a easy way to do this, is running ser2net.

For all who are not familiar with the serial port:

But there is one tricky thing, you have to consider when using ser2net:

Inside ser2net.conf you will find some lines like this here:

15000:raw:0:/dev/ttyUSB0:9600 8DATABITS (more...)

How to run a java software which needs RXTX on a raspberry pi

| Nov 23, 2019
In my last posting i wrote about migrating my aircraft noise measurement station to alpine linux. There i had some problems with getting the RXTX library for Java running on a linux, which uses musl and not GNU libc6.

Why does my java application require RXTX? As stated on the RXTX page:
RXTX is a Java library, using a native implementation (via JNI), providing serial and parallel communication for the Java Development Toolkit (JDK).
Now (more...)