Nested virtualization and the network issue.

Nested virtualization [1] is a nice feature where it’s able to run a virtual machine within another. KVM [2] has support to nested virtualization [3] since 2010 (if I’m not wrong) and you can use it to test virtualization features and/or aspects in a different Linux distribution, or even Windows system. I use this sometimes when I need test some Kimchi [4] patch I’m working in different distros to make sure the solution will work.

However, when you start up a VM using NAT configuration on top of the main hosts system (let’s call them VM-master and host-master) the network interface of the VM will get an IP in the range of and 192.168.254. This is the default configuration of libvirt+qemu on the most of the distros and when you start up a nested VM (let’s call VM-guest) it will start with the same configuration (because of the default configuration on VM-master) and you will not able to connect getting this error:

 libvirt: error : internal error: Network is already in use by interface eth0

The solution is quite simple. You only need edit the /etc/libvirt/qemu/networks/default.xml file on the VM-master and change the IP configuration that the VM-guest will work on:

$ sudo vi/etc/libvirt/qemu/networks/default.xml


$ sudo systemctl restart libvirtd.service

After this, start up your VM-guest and you will be able to connect now.



GitHub Guides: learning how to work with GitHub.

One of the open source projects or services I really like is GitHub. There you can create your, not only, software projects and use all the huge and great infrastructure to do the version controlling, documentation, issue controlling of your project. In addition, as one of the laggiest computing communities there are, you can easily discover, reuse and contribute to more than 24 million projects.

To help those developers who don’t know how GitHub works, they made available a serie of quick guides explaining each one of it’s most important features and solutions. It’s called GitHub Guides and it’s available at The first guide, in my opinion, is the most important of all guides because explain how the GitHub Flow works. It’s simple and obvious for some experienced developers, but very important for the newcomers.

Also, GitHub provided a several of video guides and trainings explaining how to integrated GitHub with other tools or get mastered in their products. Watch them here:

For those interesting in which projects I’ve been contributing or created, check out my profile there:

Emoção x Motivação

Uma tradução livre de um trecho de um artigo do LifeHacker que achei interessantíssimo:

“Da próxima vez que você não quiser fazer algo, pare, respire e pergunte a si mesmo: “Desde quando eu preciso sentir vontade de fazer alguma coisa, a fim de fazê-lo?” E, em seguida, apenas faça. Isso é muito, muito poderoso. Se precisássemos de vontade para fazer alguma coisa, a fim de fazê-lo, não teríamos sequer saído da cama de manhã, certo? Basta nutrir este pequeno mantra na sua mente por um mês, e sua vida mudará realmente.”