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Screencasts on Ubuntu

For a colleague I just made a screencast of a problem we were discussing. I was trying to use the minimum amount of tools in Gnome/Ubuntu and wanted to share the proces with you all.

Goal: Create a screencast recording of my desktop with narrated (recorded) audio at the same time.

If you are very curious and want to see the result immediately, look at the video below:

“Apache Kafka files store data without encryption”

I use Pop!_OS 21.04, which is based of Ubuntu. In Pop!_OS I use Gnome with Wayland.
All the instructions below will work with Ubuntu and any Ubuntu based distribution as well.

This howto is divided in several sections:

  • Desktop (Video) recording
  • Audio recording
  • Putting the video and audio recording together

Additional tools used in the video:

  • Show the webcam (guvcview)
  • Written annotation on a page (xournal++)
  • Written annotation on screen (Draw On You Screen)

Video recording:

Since I want to use the most simple method, my approach is to use the built-in screen cast ability in Gnome.

Press Ctrl+Alt+R to start the screen cast recording.

When the recording is in progress, you see a red filled circle in your notification area:

When you press Ctrl+Alt+R again, the circle disappears and the recording is saved to the Videos folder in your home folder:

Note: This video file is without audio.

Audio recording

As the most simple solution I used the builtin Sound Recorder in Gnome:

Press “Record” to start your recording and click “Done” when you would like to end your recording. You can see me pressing the buttons in the recorded screen cast.

Important: You need to press the screencast start keyboard command Ctrl+Alt+R and the Record button at the same time, or your video and audio will be out of sync.

When you stop the recording, the Ogg Vorbis file will be saved in the default location in your home folder, which is: ~/Recordings.

Combine the video and audio

Right now you have two separate files, not really useful when they are not combined.

To combine them, I used the following command:

ffmpeg -y -i Videos/Screencast\ from\ 05-12-2021\ 02:51:06\ PM.webm -i Recordings/Clip\ 5 -map 0:v -map 1:a -c copy file.webm

Explanation of the command:

ffmpeg
 this is the command itself
-y
 overwrite output files without asking
-i {file location}
 input file + file location
 Note that there are two input files (video & audio)
-map
 Designate one or more input streams as a source for the output file. The number is the first (0) or second (1) input file. The map itself shows what we are using in the output. In this case it is 0:v to use the video for the first input file and 1:a to use the audio of the second input file
-c copy file.webm
 Specify the output file, in this case it will be copied to file.webm in the same directory as where you run the command.

The result is what happens here:

GIF recording of putting the video and audio together (Recorded with Peek GIF Recorder)

This is the minimum necessary to create a screencast!

For example, you can send this webm video output file to people over email / file share / whatever you’d like. You can also upload it to Youtube, which can process the output file and you are done to spread some knowledge!

Add some extra spice to your screencast

To add some engagement with whoever will view your screencast, you can show your own webcam in the screen. You can use the built in program Cheese

Another option is to use guvcview, which has a cleaner interface (no buttons on the webcam output window)

Install with sudo apt install guvcview , start the program with guvcview.

Then select your video input device. You can minimize the settings pane so that you’re left with only the video of your webcam for the introduction/conclusion of your video.

Annotation

For annotation I use Xournalpp (xournal++) which helps me in drawing with my XP-Pen drawing tablet. I think it makes the screen cast a bit more entertaining compared to showing plain text but you can decide for yourself.

You can also use a Gnome Extension called Draw on You Screen by Abakkk, with this extension you can do annotations directly on the screen and thus show your thoughts / comments / pointers on screen directly.

Note: I don’t use this extension in my example video though.

Conclusion

I hope this blog post helps you in creating screen casts with the simplest possible tools. Good luck and hope to see your videos around on the web!

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Use Skype with microphone in your Citrix Receiver session on Linux

Today I wanted to join a meeting but I was unable to be heard.
I’m connected to a Windows desktop via Citrix Receiver, I’m connecting from an Ubuntu Linux host.
Looking at the sound settings in my windows desktop, I saw that there was no recording device. So not being able to send sound makes sense then.
To enable input sound, add the following line to the WFClient section in your personal ICA settings file:
 
~/.ICAClient/wfclient.ini

[...]
[WFClient]
AllowAudioInput=True
[...]

Next, log off and log back into to your windows desktop and check the recording tab on the Sound settings, there a recording device now.
2018-08-31 08:20:43 screenshot
That should do the trick.

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Citrix Receiver on Linux: SSL Error 61 ("You have not chosen to trust")

Important:
If you don’t know or understand certificates / root and intermediate certificate authorities, get someone who understands to follow below instructions.

I tried connecting to the company’s citrix server, but kept hitting the same error when I tried to open the connection:

Contact your help desk with the following information:
You have not chosen to trust "INSERT YOUR CA HERE",
the issuer of the server's security certificate (SSL Error 61)

It seems that Citrix has an alternate directory where it stores it’s trusted cert’s / certificate authorities. Even though you can see that the server’s certificate is trusted (by root CA’s) via a web browser, we need to copy those to the correct directory.
In short: Copy the root and intermediate CA’s to this directory: /opt/Citrix/ICAClient/keystore/cacerts
Continue reading “Citrix Receiver on Linux: SSL Error 61 ("You have not chosen to trust")”

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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 extensions.gnome.org.
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.

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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”

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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:
[code title=”contents of numbers.txt:”]
One
Two
Three
Four
Five
[/code]
If I just want to remove the line which begins with “Four”, I can check my sed command like this:
[code title=”Terminal output:”]
joris@beanie ~
$ diff <(sed ‘/Four/d’ numbers.txt) numbers.txt
3a4
> Four
[/code]
Awesome possum, now I know my sed command won’t destroy anything.

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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:
[code gutter=”false”]
[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-1.8.0.31-3.b13.fc21.x86_64/jre/bin/java.
[joris@today ~]$
[/code]
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:
[code gutter=”false”]
[joris@today ~]$ sudo alternatives –config java
There are 2 programs which provide ‘java’.
Selection Command
———————————————–
* 1 /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.31-3.b13.fc21.x86_64/jre/bin/java
+ 2 /usr/java/latest/bin/java
Enter to keep the current selection[+], or type selection number:
[/code]
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!

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Dynamic HTTP endpoint in Oracle Service Bus 12c based on values in a database routing table

This article outlines how to set a dynamic endpoint in an OSB HTTP Business Service. The endpoint is retrieved from a routing table which resides in an Oracle 12c database.

Components used for this solution:

  1. Ubuntu Linux 14.04 64bit
    1. JDeveloper, running the Quick Start Oracle Fusion Middleware suite
      1. Oracle Service Bus 12c
      2. Oracle Weblogic 12c
      3. OSB Project location:
        1. https://github.com/visscher/Fusion/tree/master/DBRouting
    2. Oracle Virtualbox Developer Days image for DB 12c, running:
      1. Oracle Database 12c
    3. Oracle SQL Developer 4

This picture shows the running solution in the OSB test console:
Oracle Service Bus Console 12c : Pipeline Testing - DBRouting_v1Pipeline - Google Chrome_019

Database table preparation

We need a routing table in our schema, I’m using this table setup:

CREATE TABLE "C##JORIS"."ROUTINGTABLE"
  (
    "ROUTE" VARCHAR2(50),
    "ENDPOINT" VARCHAR2(100)
  );
Where ROUTE stands for the identifier and ENDPOINT is the HTTP endpoint we try to reach.
I’ve inserted two rows:
Insert into ROUTINGTABLE (ROUTE,ENDPOINT) values ('SalesOrder','http://localhost:7101/salesEndpoint');
Insert into ROUTINGTABLE (ROUTE,ENDPOINT) values ('FinanceReceipt','http://localhost:7101/financeEndpoint');
These two endpoints will point to very simple OSB services which we will create in a moment.
Selection_022

Weblogic configuration: JDBC Data Source

We need to configure a JDBC data source in our Weblogic server, this data source is used by the XQuery function to execute SQL.
Start JDEVeloper, select your integrated Weblogic Server and start it up.
When your domain is started, open the WLS Console:
http://127.0.0.1:7101/console/
Login and open the Data Sources summary:
Selection_020
Navigation in Console: DefaultDomain - Services - Data Sources
Create a new datasource, in my example I use the JNDI name “LocalDB“
When you’re done with the configuration, test the datasource to make sure all is well:
Selection_021
The status message will be green and show a check mark if you’ve configured your data source correctly.

JDeveloper: Oracle Service Bus project

If you import the DBRouting project from here, you should have all the necessary services.
I will only discuss the assign steps which are needed in the DBRouting_v1Pipeline.pipeline.
Selection_023
There are three assign actions:
1.) Assign $route: node-name($body/*[1])
This assign determines our routing key. It is the same key as
the first column in the routing table.
The XPath here is used to select the name of the first node
but you can change this to what you want to route on.
2.) Assign $query: 
fn:concat("select ENDPOINT from ROUTINGTABLE where ROUTE = '", $route, "'")
This assign determines the query which will be executed in
the next step. We want to select the ENDPOINT which belongs
to the ROUTE which was assigned in step 1.
3.) Assign $query: 
(fn-bea:execute-sql(
 xs:string("LocalDB"),
 xs:string("ENDPOINT"),
 $query
 )/*:ENDPOINT)[1]
This assign actually executes the SQL query to our database,
which is the first argument.
The second argument names the re-occurring rows, in this
case "ENDPOINT".
The thirst argument is the query to execute.
The XPath after the execute-sql statement is to make sure
we only get one endpoint.
4.) After those assigns, we use place a task “Routing Options” in the HTTP Route node:
We only use the “URI” Routing Option:
$endpoint/text()
Selection_024
This ends the article, if you execute the pipeline you will see the endpoint has become dynamic, it is retreived from the routing table:
Oracle Service Bus Console 12c : Pipeline Testing - DBRouting_v1Pipeline - Google Chrome_019
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Start JDeveloper on Ubuntu Linux for Fusion Middleware SOA Suite 12c

Okay, this was a bit awkward, I installed the quick start 12c Fusion Middleware and was well underway to getting it all up and running.
Untill I closed JDev and couldn’t find the executable anymore..!
For anyone who had the same embarrassing situation, it’s located here:

*MiddlewareInstallationFolder*/jdeveloper/jdev/bin/jdev