Oracle VM Server: Pool is locked forever

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 other change would do the job, but this is a minimal change, which solves the problem...

Hopefully there will be an update, so this problem will disappear in future versions.

Microsofts Visual Studio Code on Linux

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 https://code.visualstudio.com/ 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 - less a second.

Within Visual Studio Code it is very easy to install some extensions:

Running a small javascript program is very easy. I just entered these lines and without any further configuration running the program or debugging was no problem:

 

Linux ser2net: no connection to /dev/ttyUSB0

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:
https://en.wikipedia.org/wiki/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 NONE 1STOPBIT 

This means: on port tcp 15000 you can access the serial port /dev/ttyUSB0 (if you have a USB to serial adapter in place).

If this does not work, check the ports with

root@ubuntu:/home/ubuntu/dfld# netstat -lntup |grep ser2net
tcp6       0      0 :::15000                :::*                    LISTEN      1361/ser2net        

As you can see, it only listens on TCP6. So you have to reconfigure this to

127.0.0.1,15000:raw:0:/dev/ttyUSB0:9600 8DATABITS NONE 1STOPBIT

If you only want to access this on localhost (which is very nice security enhancement ;-) ).
And after a restart of ser2net everything works like expected:

root@ubuntu:/home/ubuntu/dfld# netstat -lntup |grep ser2net

tcp        0      0 127.0.0.1:15000         0.0.0.0:*               LISTEN      

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

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 i wanted to move to a raspberry pi. But this runs on ARM and the RXTX is only provided for x86/x64 systems.

But there is another way: ser2net

With this proxy /dev/ttyUSB0 can be mapped to a tcp port and java can access this without using RXTX.