Although GNOME Shell integration extension is running, native host connector is not detected

This is a bit of a nuisance, after a fresh install of Ubuntu Gnome, I was not able to install extensions from

Firefox asked me if I’d like to install the extension but after a Firefox restart I still wasn’t able to install any plugins.

To be precise; this message was shown:

Although GNOME Shell integration extension is running, native host connector is not detected. Refer documentation for instructions about installing connector.

The solution was to install the chrome-gnome-shell package;

sudo apt-get install chrome-gnome-shell

This fixes the message from both chrome and firefox.

Remove duplicate lines while comparing two files

I’ve been quite busy this whole day with a partially complete database dump and wanted to prepare for tomorrow with some ninja bash voodoo shizzle. I’m doing a braindump here because I know I’ll have forgotten this when I wake up tomorrow :-)

The command stated below was the first working example I’ve gotten together, please let me know if you know a neater / better solution!

The situation:

I’ve got two files. The first file contains lines which need to be deleted from the second line (if they exist there) Continue reading “Remove duplicate lines while comparing two files”

Comparing sed stream output in linux

Sed is very very powerful, which is a good thing to be aware of.
I was looking to compare the output of a sed command to the original file before I wanted to execute the sed command directly on the file and came across this handy trick.

It works by using temporary named pipes inside the diff command.

Contents of file:


If I just want to remove the line which begins with “Four”, I can check my sed command like this:

joris@beanie ~
$ diff <(sed '/Four/d' numbers.txt) numbers.txt
> Four

Awesome possum, now I know my sed command won’t destroy anything.

Easily switch between java versions using alternatives in Linux

This approach works in several distros, I’ve been using it in Ubuntu for a while and just used it in Fedora as well.

As a developer, you might need to switch between java versions often, this approach will come in handy then.

We will be using the command “alternatives”, in this case to check the configuration of your Java installation. The default is most often OpenJDK, while you might need Oracle Java.

Run “alternatives –display java” to see which versions you can currently choose from:

[joris@today ~]$ alternatives --display java
java - status is manual.
 link currently points to /usr/java/latest/bin/java
Current `best' version is /usr/lib/jvm/java-1.8.0-openjdk-
[joris@today ~]$ 

There’s no Oracle Java yet, make sure you’ve installed Oracle Java. If you haven’t, you can check this blog post: Install Oracle Java in Fedora, Red Hat or CentOS using Yum and RPM

When Oracle Java is installed, you can add it to your alternatives: “sudo alternatives –install /usr/bin/java java /usr/java/latest/bin/java 20000”

Please note: I used “latest” in the command above, another options is to specifically set the version you want. This way you can install several JDK’s and switch as shown below.

When that is finished, you can select your current flavour of Java:

[joris@today ~]$ sudo alternatives --config java

There are 2 programs which provide 'java'.

  Selection    Command
*  1           /usr/lib/jvm/java-1.8.0-openjdk-
 + 2           /usr/java/latest/bin/java

Enter to keep the current selection[+], or type selection number: 

Choose the option you want to switch between Java versions.

As mentioned by enkouyami, please check if you need to use update-java-alternatives instead of alternatives. The use of alternatives was valid when I wrote the post, but might not be working anymore!

Find Java JRE location on Ubuntu Linux

Everybody knows that the java executable is located in /usr/bin/java , but what if you need the JDK / JRE location itself?

Just using “whereis” will not get you there, that will point you to the /usr/bin/java point.

joris@howlingmad: ~_011


So, let’s find out a but more about /usr/bin/java:

ls -l /usr/bin |grep java

joris@howlingmad: ~_012


Awesome, this will lead us somewhere, it’s a symlink to /etc/alternatives/java

So let’s do the same there:

ls -l /etc/alternatives/ |grep java

And we’ve hit the jackpot, among the lines here, there’s a bunch of lines pointing us to the JRE location:

joris@howlingmad: ~_013


As you can see in the screenshit, our java executable within the JRE location is:


Which means the JRE location is:





Oracle SQL Developer 4 does not run on Oracle Java 7 on Ubuntu 14.04

Wow, ain’t this awkward :-). I cannot run Oracle SQL Developer 4 (4.0.2) on Ubuntu with Oracle JDK 7..

To be complete: when running SQL Developer with JDK 7 from Oracle itself, displays the following error;

joris@dipshit:~/programs/sqldeveloper$ ./
Oracle SQL Developer
Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
LOAD TIME : 968#
# A fatal error has been detected by the Java Runtime Environment:
# SIGSEGV (0xb) at pc=0x6aa69be0, pid=9537, tid=1836366656
# JRE version: Java(TM) SE Runtime Environment (7.0_65-b17) (build 1.7.0_65-b17)
# Java VM: Java HotSpot(TM) Server VM (24.65-b04 mixed mode linux-x86 )
# Problematic frame:
# C 0x6aa69be0
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
# An error report file with more information is saved as:
# /home/joris/programs/sqldeveloper/sqldeveloper/bin/hs_err_pid9537.log
# If you would like to submit a bug report, please visit:
/home/joris/programs/sqldeveloper/sqldeveloper/bin/../../ide/bin/ line 1193: 9537 Aborted (core dumped) ${JAVA} "${APP_VM_OPTS[@]}" ${APP_ENV_VARS} -classpath ${APP_CLASSPATH} ${APP_MAIN_CLASS} "${APP_APP_OPTS[@]}"

Solution: Run Oracle SQL Developer with OpenJDK

First we’ll need to install OpenJDK:

sudo apt-get install openjdk-7-jdk 

Then we’ll need to change the path which SQL Developer uses. This was asked once when you first started it and it is saved in the following path:


The file [[ product.conf ]] contains the value SetJavaHome, we need to change this to the OpenJDK path;

If you're running 32 bit Ubuntu:

SetJavaHome /usr/lib/jvm/java-7-openjdk-i386

Or if you're running 64 bit Ubuntu:

SetJavaHome /usr/lib/jvm/java-7-openjdk-amd64

After saving this change, you can start SQL Developer on Ubuntu 14.04 and it will use OpenJDK 7, without changing your regular Java settings!