Michel Didier Joomun's Blog

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Tuesday 28 October 2014

sec_error_ca_cert_invalid - Firefox 33

Still having trouble accessing your self-signed sites like intranets using firefox ?

As of firefox 33, mozilla::pkix is the enabled by default and can't be disabled via about:config. More info on this link

In order to access your intranet and dev websites using self-signed, you must also check if the server is correctly configured.

Comment SSLCertificateChainFile directive in your vhost configuration (picture below) if there is any and it should be OK.


Sunday 31 August 2014

Building a virtual computer lab environment with open source software

Hi everyone,

It's been a long time since I have not written a post and ss you can see, i'm no longer on wordpress but on dotclear :)

This time, I would like to talk about something sysadmin are always needing in order to do proper research and analysis, a computer lab environment.


We are always needing one when we want to test out the latest features in mysql, apache or some more advance features like loadbalancing, MQ, firewalls, cache etc..

10 years ago, i was using physical PCs (intel PII and PIII, they were already outdated but I got those at very low prices ) to do the job but using those costs a lot and need a lot of maintenance. So we'll turn to a much more scalable and cheap solution, virtualization.

Nowadays, there is a lot of virtualization solutions out there, we speak a lot about cloud, VPS and all that stuffs. We'll try to look at some of those solutions and some lesser known such as UML.

We also have cloud computing sotware such as openstack which provides a complete environment for managing VMs. They generally provide enterprise features such as migrating VMs, High availability with control through and central management consoles,

Here are some of the solutions available and their common uses :

Linux Containers (Paravirtualization)

UML as its name suggests will work only on linux but can be a very good way to make simple and light VM. Netkit, although not maintained anymore provide a very simple way to create a lab of multiple servers, with multiple NICs and apps with custom configuration on server start. Marionet , like netkit provides a graphical interface but do the same job. Those two are most commonly used for network labs but can also be used for testing apps.


Openvz is a very simple solution to virtualize your lab. The vz tools allow to easily create and configure the servers. The main disadvantage is that a custom kernel is needed. There are also some open source web management panels out there but my favourite is OVZ

LXC on the other hand is gaining a lot of popularity and is becoming the de facto of containers on Linux. I found the tools intuitive but guess it's only because of lack of pratice.

Most of those method can also be driven by libvirt, the virtualization swiss-army. Check it out

Full virtualization

With the advances in CPU, mostly Intel VT-x and AMD-V, we can now have fully virtualized systems ! This means that we can now run a windows, solaris or BSD on top of a linux hypervisor

Here are the most popular open source solutions for full virtualisation

VirtualBox Xen KVM (modified Qemu)

Mobile / handheld / device lab


Even mobile and handheld can be virtualized or emulated. This will enrich your labs.

Some proposed solutions :

Automating lab

Installing OS

Many of those cloud computing softwares provides OS as images. Installing and OS is now easy as choosing and image at download it. The images are generally preconfigured with bascis apps such as WEB or Database servers,

Upgrading thoses OS can be more complicated though and waiting for a new image might be a better choice apps must be reinstalled.

With full virtualized systems installed manually like on Virtualbox, we could use PXE for remote automated install.

One of the nice features of netkit was the lab config, it allows you to quickly build a huge lab of UML instances (servers) with a simple text file.

Vagrant, a deploying tool also allows this and the best is that it has a libvirt support through a plugin, thus allowing to quickly build labs of different virtualization techs.

Installing and maintaining applications

Deploying apps can rapidement become a headache if we have more than 10 VMs. Puppet, salt or fabric can be used to automate this process. An agent may be needed on the servers in order for them to benefit those automations.


Those management software are often used with another great app, Docker.

Docker allow deploying and maintaining applications in a very intuative way. Most of all, it allows downloading and executing of thoses images on different linux systems through LXC.

Lab console management

There are a lot of web interfaces for the different technologies presented. Check out those proposed for libvirt. As libvirt can be used to managed most of those virtualization solutions, it could be a good start.

Hope that this post has helped you make your choice for building up your virtual computer lab.

In the next post, we' ll try some hands-on and begin building the lab :)


Didier Joomun

Wednesday 1 January 2014

dimension specifications for scale modeling

Hello everyone and happy new year !!

Yeah, it's already 2014 and hope this year will be full of creativity :)

What new paper model could I build this week ? Was thinking of a nice construction truck be soon realised that it could be difficult if I have no precise dimension of one of those trucks. I was hoping to find some forums or sites regrouping some useful links for those specs but did'nt see any.

Tha'ts why I wanted to write this post. We'll begin this some website I found on the net. You'll find use info such as tyre size, vehicle dimensions, helicopter blades lenghts, etc...

Please comment if you know some useful links and i'll add them to the main list.


Boeing - For commercial and military aircrafts. Ex : The CH-47 chinook


http://www.ritchiespecs.com/ - great for constructions vehicles

Carspector Lots of info about cars, engine location, dimesions but lacks of drawings

And you, where do you get your specifications for modeling ? :)

Saturday 28 December 2013

Modeling a soldier with plasticine

Hello modelers,

Just bought some basic crafting tools at Hobby world (Hassamal) in Curepipe, Mauritius. They got a lot of stuffs there like resin, latex for moulding, cutting mat and much more.

One of my targets is to build my own moulds and make my own figurines. As an exercise, I tried to make a soldier figurine with plasticine, taking a small soldier toy as example. The result is not a great as expected but looks nice anyway.

Here are some pictures of the model, sorry for bad quality :( :



Some handy tools for plasticine modeling, also bought at hobby world for less than Rs100 :

plasticine modeling tools

This was only a little pratice, i'll try to make one with auto-hardening clay and used it as model for latex mould. The mould would then be used for resin casting.

Nice week-end and happy modeling :)

Thursday 26 December 2013

Simple 3D paper modeling - Custom tank

Hi there,

For all those starting with paper modeling, here's a quick and dirty tank model.



The model was drawn using Qcad on linux.

The only tools needed are

  • Small scissors
  • Paper Glue
  • Pencil
  • Printer, to get more precise drawing instead of using pencil.

After printing the model, all you have to do is cut the motif and fold it. I've used line patterns to indicate areas to glue.

The drawings (DXF and PDF) are attached to this post. The turret and barrel have been added after and henced is not included in the drawings.

The model is not perfect but hope you'll have fun with it and try your owns !

See you :)