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

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”)”

Calibre will not open, Gdk-Warning, drawable is not a native X11 window

It’s been a while since I’ve used Calibre to manage my Kindle, but today I wanted to transfer some PDF’s.

Unfortunately Calibre stopped working as soon as I tried to open a dialog window.

As it seems, Fedora has adopted a new display server, called Wayland. Since Calibre has dependencies in the previous adoption X-Server, Calibre won’t start.

In my case, the solution was to set a different GDK backend, before starting Calibre.


Open a terminal and enter the following command:

GDK_BACKEND=x11 calibre

Dell XPS 13 Skylake 9350 does not boot Fedora with UEFI while livecd works

I’ve been struggling to get Fedora working on my new laptop (Dell XPS 13 Skylake 9350) since I got it a couple of months ago. It was quite frustrating to have a working LiveCD (LiveUSB) but my laptop kept failing to boot Fedora.

Today I’ve found the problem and the fix was easy.

After the installation the EFI boot partition contains a fedora directory

( /boot/efi/EFI/fedora )

Contents of the fedora directory:

├── fonts
│   └── unicode.pf2
├── fw
├── fwupx64.efi
├── gcdx64.efi
├── grub.cfg
├── grubenv
├── grubx64.efi
├── MokManager.efi
├── shim.efi <<<< This is the one!!
└── shim-fedora.efi

The solution was to create a new Boot entry in the BIOS, this wasn’t done automatically by Fedora.

Configure the UEFI boot manager to point to the shim.efi file.

When that’s done, reboot your laptop and start using Fedora.

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.

Fedora Gnome-shell abnormal high CPU usage in combination with Intel GM 4000 videocard

I’ve been using my trustworthy thinkpad for a couple of years now, but as soon as I installed Fedora on it, it became quite slow due to gnome-shell using a huge amount of CPU power.

My thinkpad isn’t the quickest out there, it’s a dual core machine from around 2006, but 50% CPU on two cores for just Gnome was a bit excessive.

I’ve been searching a lot, and didn’t found any solution, until I started fiddling with Gnome-tweak-tool and saw the “Background logo” entry.

If you haven’t yet; Install gnome-tweak-tool with the following command:

sudo yum install gnome-tweak-tool

The background logo is an PNG overlay on your desktop, and that overlay doesn’t work well with Intel GM cards.

Start gnome-tweak-tool, disable that extention and see your CPU usage drop to 2%, which is what it should be.


Install Oracle Java in Fedora, Red Hat or CentOS using Yum and RPM

Hi guys,

This post will outline how to install Oracle Java JDK in Fedora, Red Hat or CentOS.

Please note that this will only install the JDK, when you’re done you will need to select this JDK to be able to use it. That is outlined in this blog post: Easily switch between java versions using alternatives in Linux

First determine if you need 32 or 64 bit. If you’re unsure you can check using “uname -p” in a terminal which will display your kernel and which architecture you’re using.

Next, download the JDK that you wish to use. In this example I will be installing the latest JDK from Oracle, you can find it here: Oracle Java Downloads.

I have chosen Java Platform (JDK) 8u31, which downloads the RPM.


After the download is finished, open a terminal and go to the location of the download.

Next, enter this command:

sudo yum install jdk-8u31-linux-x64.rpm

This will install the JDK.

Important: After this is done, you have placed all the files in the right location, but can’t use it until you’ve finished the steps in this blog post: Easily switch between java versions using alternatives in Linux