• Posted on

    A sensible NeoVim configuration

    I have been using NeoVim as my main editor for code since 2017. When discussing that with other engineers, a common complaint I hear about (Neo)Vim is that its configuration is overly complicated and confusing. In this post, I will try to address this point by showing simple steps to configure NeoVim into a development capable environment. This should allow you to get essential code editing features (ie. auto-completion, linting, search…) while keeping a minimalist and fast environment.

    Installing NeoVim

    First of all, install NeoVim by following the instructions on GitHub. Open NeoVim by simply typing nvim in a terminal.

    If you want to learn the basics of using vim, type :Tutor. This will take you to the built-in tutorial.

    Type the :CheckHealth command into NeoVim’s normal mode, this will tell you if you need to set up anything special.

    The most important dependency is to have python 3.6+ with the neovim pip package installed as well as node with the neovim npm package. Aside from that, you might need:

    • python 2.7 with the neovim package
    • ruby with the neovim gem
    • perl with the Neovim::Ext module

    Once everything is green, let’s go over some basic configurations

    An editing tool as technology advanced as vim
    Photo by Kenny Eliason

    Basic configuration

    First, you should create your configuration file at ~/.config/nvim/init.vim.

    To be able to exit NeoVim’s terminal emulator (:term) by simply pressing escape instead of the Ctrl+\ Ctrl+n combo, add this line to your config file (~/.config/nvim/init.vim):

    tmap <Esc> <C-\><C-n>

    map is the basic operator for mapping keyboard shortcuts. tmap indicates that you want to map these keys in terminal mode only. imap and nmap are respectively for insert and normal mode. As an alternative to map you might have to sometimes use noremap to non-recursively map (this is meant to avoid propagating to mappings you’ve already changed).

    You’ll also want to be able to switch between windows without having to type a complete command:

    nmap <silent> k :wincmd k<CR>
    nmap <silent> j :wincmd j<CR>
    nmap <silent> h :wincmd h<CR>
    nmap <silent> l :wincmd l<CR>

    These lines will map the switching of commands to Alt+hjkl. (Note, on mac the only way I’ve managed to configure that was by using the characters output when I press Alt+hjkl on my keyboard).

    Then, you can do a few tweaks to the appearance. I recommend displaying numbers next to lines, displaying line wrapping, and allowing horizontal scrolling.

    set number
    set nowrap
    set sidescroll=1

    You should then add some default tab configurations.

    set tabstop=2
    set softtabstop=2
    set shiftwidth=2
    set expandtab
    set autoindent
    set fileformat=unix

    You also want to be able to override those configurations for each project with a local .nvimrc:

    set exrc

    And lastly, this line will allow scripts to run for specific file types:

    :filetype plugin on


    Since NeoVim doesn’t have every feature developers usually need out of the box, you will need to be able to install plugins. For that purpose, we will use vim-plug. Installing by runnning:

    sh -c 'curl -fLo "${XDG_DATA_HOME:-$HOME/.local/share}"/nvim/site/autoload/plug.vim --create-dirs \

    We will then do the first edit to your configuration file ~/.config/nvim/init.vim. Add the following lines to install the plugins you will need:

    call plug#begin('~/.vim/plugged')
    Plug 'ctrlpvim/ctrlp.vim'
    Plug 'tpope/vim-fugitive'
    Plug 'vim-airline/vim-airline'
    Plug 'tpope/vim-sleuth'
    Plug 'neoclide/coc.nvim', {'branch':'release'}
    call plug#end()

    Each of the lines starting with Plug indicates the GitHub repository of a plugin. Save your config file and type :PlugInstall in NeoVim’s normal mode to install them.

    The plugins this will have installed are the following:

    • coc.nvim gives you essential code-editing features like auto-completion using the language server protocol (like VScode)


    Ctrlp.vim is a very efficient file search plugin.

    To use it simply press CTRL+P, this will open a file list that you can navigate with arrow keys. Typing any characters will make it search for matching files. You can use CTRL-F and CTRL-B to cycle between the different search modes (files, buffers, or most recently used). CTRL-R will allow you to type in regexes, while CTRL-D will search only in the filenames instead of the full path.

    The search function

    Use the following line to stop this plugin from indexing files outside of your source code:

    let g:ctrlp_custom_ignore = '\v[\/](node_modules|target|dist|venv)|(\.(swp|ico|git|svn))$'

    If you want to integrate more file handling into vim, you can also try NERDTree, which will provide you with a complete file system explorer.


    Vim-fugitive is a wrapper around git. It doesn’t require any special configuration to work, as long as you have a git CLI configured on your machine.

    It will allow you to use any git command in vim using :G, you can try it with :G status to display the result of git status. One neat trick is that you can use :G grep to send the result of a git grep directly into vim’s quickfix list.


    Vim-airline will display the status of your current file as the last line of the editor. It’s basically plug and play and will even automatically detect other plugins you use (like ctrpl or fugitive) and integrate them.

    The status line is divided into 6 sections (A, B, C, X, Y, Z) and can be customized with the statusline syntax:

    let g:airline_section_b = 'Filetype: %y'
    The resulting airling


    Vim-sleuth aims at automatically adjusting indentation to the file you’re editing. It works by simply overriding the shiftwidth and expandtab variables (which you can set manually in your config file if you want). It doesn’t require any configuration either and generally works pretty well.

    An alternative to it would be to use editorconfig-vim. This plugin will instead follow the configuration written in a .editorconfig file at the root of a project.


    Coc.nvim is really what will give you an IDE-like experience. This plugin will give you auto-complection, linting, and formatting, using language servers protocols. For that part, I recommend using the configuration sample they provide on GitHub. It will give you useful shortcuts to IDE-like features, like gd to go to a definition, gr to list references, and \t for automatic renaming.

    The rename window

    To support every possible language, CoC has its own plugin system. For example, :CocInstall coc-go will install the coc-go plugin for the Go programming language and use gopls.

    Alternatively, NeoVim now has built-in support for LSPs, you can read more about how to configure that in this repo. As this solution still requires to install a few plugins for auto-completion, I consider CoC to be the simplest option around at the moment.


    Of course, everyone loves some colors! Vim and Neovim have a ton of themes that you can example at vimcolorscheme. Each one can be installed with vim-plug like any other plugin. Once it is installed you can use the colorscheme function to enable it from your vim config file. For example with the dracula theme:

    colorscheme dracula


    This post is only scratching the surface of what can be done with NeoVim. As you use this editor more and more, you will probably want to use different configurations, and will probably end up with a few more (or fewer plugins).

  • Posted on

    Managing a Kubernetes cluster with Helm and FluxCD

    As seen in my previous article, after successfully setting up a Kubernetes Cluster you can install applications on it using the Helm CLI. This is convenient to get started but might not scale well with multiple people administering the cluster.

    To make collaboration easier and avoid making mistakes by simply mistyping Helm commands, it is recommended to adopt a GitOps workflow. This consists of using Git to version control the state of the cluster. In this article, I will explain how to use FluxCD to achieve this.

    An actual helm
    Illustraton by Loik Marras

    Getting started with FluxCD

    First of all, make sure you have a running Kubernetes cluster and have installed kubectl and helm. Then you will need to create a Git repository at your favorite provider (GitHub, Bitbucket, etc…). Once this is done, clone it locally and create a releases folder inside of it. This folder will contain the files defining your Helm releases (a release is an instance of a chart running on a cluster).

    Let’s start by creating a release for my favorite IRC client, The Lounge. To do this, create a file in releases/thelounge.yaml containing the following data:

    apiVersion: helm.fluxcd.io/v1
    kind: HelmRelease
      name: thelounge
      namespace: default
        fluxcd.io/automated: "false"
        fluxcd.io/tag.chart-image: semver:~4.0
      releaseName: thelounge
        repository: https://halkeye.github.io/helm-charts/
        name: thelounge
        version: 4.3.0
          enabled: true
            - YOUR.OWN.DOMAIN

    This will be using the chart available on Artifact Hub, and the software will be running on the default namespace, and we ask for an ingress to be created. Don’t forget to commit and push the release!

    After creating this repository, you should install FluxCD on your cluster. To do this simply run the following commands:

    helm repo add fluxcd https://charts.fluxcd.io
    kubectl apply -f https://raw.githubusercontent.com/fluxcd/helm-operator/master/deploy/crds.yaml
    kubectl create ns flux
    helm upgrade -i flux fluxcd/flux \
       --set git.url=git@github.com:[USERNAME]/[REPO] \
       --set git.branch=[BRANCH] \
       --namespace flux
    helm upgrade -i helm-operator fluxcd/helm-operator \
      --set git.ssh.secretName=flux-git-deploy \
      --set helm.versions=v3 \
      --namespace flux

    You should now see 3 pods running in the flux namespace:

    flux-memcached-869757cb88-77br8 1/1 Running 0 100s
    flux-59cb4447b9-thpr9 1/1 Running 0 101s
    helm-operator-686dc669cd-g8kn7 1/1 Running 0 89s

    Finally, you will need to give read and write access to your git repository to FluxCD. To do this, install fluxctl and run:

    fluxctl identity --k8s-fwd-ns flux

    This will print an RSA key that needs to be added as a deploy key to your repository. For GitHub users, go to https://github.com/YOURUSERNAME/YOURUSER/settings/keys/new to add the key (tick the give write access checkbox).

    Your release should start getting installed on your cluster soon. You can check the state of your helm releases by running

    kubectl get hr

    If needed, you can check the FluxCD logs with

    kubectl -n flux logs deployment/flux -f

    If you want to manually trigger FluxCD to re-read your git repository, use the command:

    fluxctl sync --k8s-fwd-ns flux
    A compass
    Illustraton by AbsolutVision

    Adding your charts

    Of course, you might not be able to do exactly what you want using the charts publicly available. FluxCD allows you to add your charts directly through Git.

    First, create a charts directory. Inside this directory, run the following command to create a chart named mychart:

    helm create mychart

    This will generate a sample chart defining everything that’s required to launch an Nginx server in production. To run this chart, you will have to define a release for it in your releases folder:

    apiVersion: helm.fluxcd.io/v1
    kind: HelmRelease
      name: myrelease
      namespace: default
        fluxcd.io/automated: "false"
        fluxcd.io/tag.chart-image: glob:3.1.1-debian-9-*
      releaseName: myrelease
        git: ssh://git@github.com/[USER]/[REPO]
        ref: [BRANCH]
        path: charts/mychart
          enabled: true
            - host: YOUR.OTHER.DOMAIN
              paths: ["/"]

    Like in the previous example, don’t forget to git commit and git push. FluxCD will automatically create the new release and you will see a magnificent Nginx welcome page appear at the specified domain.

    To be able to display something else than the Nginx welcome page, we will give it a configuration file. For this purpose, you can define a configmap in charts/mychart/templates/configmap.yaml. The following config will redirect every request to a URL of our choice:

    apiVersion: v1
    kind: ConfigMap
      name: nginx-conf
      nginx.conf: |
        events {
          worker_connections  1024;
        http {
          server {
              listen 80 default_server;
              return 301 {{ .Values.redirect }};

    You will then need to declare the volume by adding this value to spec.template.spec in charts/mychart/templates/deployment.yaml:

          - name: nginx-conf
              name: nginx-conf

    To mount the configuration file into the Nginx container, you need to add the following lines to spec.template.spec.containers[0] in the same file:

              - mountPath: /etc/nginx/
                readOnly: true
                name: nginx-conf

    Finally, bump the version in charts/mychart/Chart.yaml, and set the redirect URL in releases/myrelease.yaml by editing the values section like this:

          enabled: true
            - host: YOUR.OTHER.DOMAIN
              paths: ["/"]
        redirect: "https://www.youtube.com/watch?v=cFVF26XPcAU"

    Dive deeper

    As this article only really scratches the surface of what Helm and FluxCD can do, I recommend you to also check out the official FluxCD docs and their example repository, as well as the Helm Chart Template Developer’s Guide.

    The source code for the examples shown in this article is available on GitHub.

  • Posted on

    Self-Hosted Kubernetes with k3s

    Kubernetes has been the center of attention of the DevOps community for a few years now. Yet many people find it too daunting to try it out for personal uses. Running a single-node Kubernetes cluster for self-hosting is however not that complicated. In this article, I will show you how to create this using k3s which is a lightweight distribution of Kube.

    Preparing the server

    Before launching anything Kube related, you might want to make sure the access to your server is secured. Follow this guide for instructions on how to disable root login and enable public-key authentication if it’s not already the case.

    I have encountered issues running k3s with the newer version of iptables (nftables) which comes enabled by default on many distributions (like Debian 10). You can check whether or not you’re using nftables with sudo iptables --version. You should switch back to the legacy iptables by executing:

    sudo update-alternatives --set iptables /usr/sbin/iptables-legacy 
    sudo reboot

    It’s also a good idea to set-up basic firewall rules to filter incoming traffic. I apply these rules for the eth0 interface which handles my server’s internet connection (find yours using ip a):

    sudo iptables -A INPUT -i eth0 -p tcp --dport 22 -j ACCEPT # Allow SSH
    sudo iptables -A INPUT -i eth0 -p tcp --dport 6443 -j ACCEPT # Allow kube API
    sudo iptables -A INPUT -i eth0 -p tcp --dport 10250 -j ACCEPT # Allow kube metrics
    sudo iptables -A INPUT -i eth0 -p icmp --icmp-type 8 -j ACCEPT # Allow ping
    sudo iptables -A INPUT -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT # Allow responses to our requests
    sudo iptables -A INPUT -i eth0 -j DROP # Drop every other incoming packets

    Don’t worry about opening ports specific to the applications you want to run in your cluster since k3s will handle it directly. To persist your iptables rules after a reboot, I use the iptables-persistent package.

    sudo apt install iptables-persistent
    sudo iptables-save | sudo tee -a /etc/iptables/rules.v4
    Too many servers
    Illustraton by Taylor Vick

    Installing k3s

    The shell script located at https://get.k3s.io is meant to install k3s automatically. You can directly execute it by running:

    curl -sfL https://get.k3s.io | sh -

    You can check that the service is running by doing

    sudo service k3s status

    You can already run basic kubectl commands from your server’s shell. We can check that everything is up and running with the cluster-info command.

    sudo k3s kubectl cluster-info
    #Kubernetes master is running at
    #CoreDNS is running at
    #Metrics-server is running at
    #To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.

    Use kubectl and helm

    Now you will probably want to use kubectl to control your cluster without being logged in to your server. You will find the instructions on how to install kubectl on your local machine here To do this, you can find the configuration used by k3s at /etc/rancher/k3s/k3s.yaml, copy it to ~/.kube/config. Alternatively, you can pass the config to kubectl with the --kubeconfig option. You will need to change the server IP in this configuration from to your server’s external IP address.

    Now run the kubectl cluster-info command locally and you should see results similar to what you had on your server. A few useful kubectl commands to keep in mind are:

    • kubectl get pods -> list the running pods
    • kubectl top nodes -> show the used resources on your nodes
    • kubectl logs [pod_id] -> show the stdout of a pod

    To make the installation of software easier on your cluster, helm will act as a package manager. Install helm on your local machine by following these instructions or just run this if you’re on Linux and trust their install script:

    curl https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 | bash

    Helm’s packages are called charts, they are a set of templates defining how to run specific software in Kubernetes. You can now start looking at the available charts in the Helm Hub or with the built-in command helm search hub [name]. For example, if you want to install The Lounge (a very good self-hosted IRC client/bouncer). You will first need to add the repo that contains its chart:

    helm repo add halkeye https://halkeye.github.io/helm-charts/

    Running helm install will then be enough to setup Thelounge. Since you might want to access it through a specific domain, we will also ask helm to set up an ingress for it, by giving it additional options to the chart. This gives us the full command:

    helm install thelounge halkeye/thelounge --version 4.0.6 --set ingress.enabled=true --set ingress.hosts.0="my.domain.com"

    Your cluster should now be ready for any software you want to run. In a next article, I will explain how you can make better use of helm to keep track of the applications you host.

  • Posted on

    Low Tech Crypto : ThreeBallot

    Previously in this blog, I have mentioned that cryptographers designed algorithms allowing us to conceal messages without the use of a computer, like Solitaire. Although message privacy is the first subject that comes into everyone’s mind when talking about cryptography, it has many other applications, one of them being the design of secure voting systems. In this post, I will talk about ThreeBallot voting system, a system designed by Ronald Rivest (the R in RSA) which aims at creating a secure voting protocol entirely based (almost entirely) on paper ballots.

    Someone voting during french elections
    Illutration by Arnaud Jaegers

    End-to-end auditable voting systems

    Before we start taking a look at ThreeBallot, we need to summarize the objectives of cryptographic voting systems. In general, cryptographic voting systems aims at being end-to-end auditable, which means two things:

    • Anyone can proceed to a recount
    • Every voter has a way to know if their vote was counted

    This second property is usually achieved by giving a receipt of its vote to the voter. However, this receipt should not contain enough information to allow an attacker to breach the privacy of the vote, as each vote must remain secret to avoid vote-buying or coercion.

    Introducing the multi-ballot

    A sample ThreeBallot multi-ballot
    A sample ThreeBallot multi-ballot

    The ThreeBallot system aims at solving this problem with the use of a “multi-ballot”. The multi-ballot is a voting ballot that can be split into 3 parts (one per column), all containing the list of candidates (one per row) with optical-scan checkboxes as well as a unique identifier. To vote, simply check 2 boxes on the row of the candidate you want to vote for, and 1 box on the row of each candidate you want to vote against. A ballot will be considered spoilt if all three boxes for a candidate are checked, or none for another candidate.

    A sample filled ThreeBallot multi-ballot
    A sample filled ThreeBallot multi-ballot

    The validity of the ballot will need to be checked (by machine) before being split into 3 separate ballots. The voter will then chose which parts of the ballot to be used as a receipt and receive a printed copy of it, before casting the 3 ballots.

    A receipt
    A single ballot, used as receipt

    When the election is complete, every ballot is displayed publicly. Anyone can proceed to a count, the results are inflated by the number of voters (one box as to be checked minimum) but the difference between candidates will remain the same. The voters can each check that their ballot appears with the correct vote and ballot ID, or contest the vote using their receipt. The voters cannot use their receipt as a proof of having voted for a candidate, as you need at least 2 of the 3 ballots to tell that, thus maintaining vote secrecy.


    Despite looking very good on paper, this voting system sadly has many practical vulnerabilities. First of all, despite being paper-based it still requires a machine to print ballots with unique identifiers, and another one to check the validity of the ballots before casting them. Both of these machines represent weak points of the system, as one of them failing would stop the election from taking place correctly. A single malfunction of the checker machine would also be enough to make the entire election null because the system doesn’t provide any way of spoiling a vote after it’s cast. Privacy breaches could also happen if these machines were to be compromised, as an attacker could record which identifiers are part of the same multi-ballot and use it to connect receipts to a full ballot.

    In a follow up paper, Charlie Strauss points out that voter coercion can still happen with methods as simple as asking the voter to take a picture of their ballot using a smartphone. According to Strauss, it would also be trivial to double or triple vote by modifying the ballot after having validated it and before casting it. Voters might also give away their receipts or simply throw them in the nearest trash can, making their vote non-auditable and giving an attacker the opportunity of changing them.

    In a second paper, Strauss also points out the cryptographic weakness of ThreeBallot. Since one part of the multi-ballot restricts choice on the two other parts (a candidate can’t be entirely blank or checked), the receipt is leaking information about the actual vote. Combining this information with voter bias (ie. party preference), and the publicly displayed ballots, it becomes statistically possible to link a receipt with its two other ballot parts. This is especially concerning in a situation where the attacker could coerce the voter into not only voting for a specific candidate but also checking a specific pattern on its ballot.


    Many improvements to the ThreeBallot voting system have been suggested, but as with many security protocols, improving security often comes with useability issues. This led to the slow abandonment of this protocol. However, the insights gained through ThreeBallot later allowed the creations of new secure voting systems, such as Scantegrity, which was used in actual elections by the city of Takoma Park, in 2009 and 2011.

  • Posted on

    FOSDEM 2020 recap

    This year was the 20th edition of FOSDEM, and the third time I managed to attend it. FOSDEM is a yearly Free & Open Source Software meeting taking place in Brussels, Belgium and organized by the Free University of Brussels (ULB). This edition gathered more than 8000 FOSS enthusiasts from all around the world for 837 talks, making it an exceptional event for anyone interested in learning more about open-source projects and communities.

    The city of Brussels
    Illutration by Yeo Khee


    One of the very first talks I managed to see this year was about SpecFuzz, a tool made by Oleksii Oleksenko and his colleagues to help to test against Spectre vulnerability. The talk does an amazing job of explaining what causes the new speculative execution vulnerabilities, how can we detect them and how can we fix them. Since there’s no doubt these vulnerabilities will remain a major hardware and software security issue it’s an essential talk for anyone wanting to understand the topic. If you want to know more about SpecFuzz, Oleksii Oleksenko’s paper is available on arXiv and the source code is on GitHub.

    Then I managed to see two talks about Falco, a new Kubernetes threat detection engine. The first one by Lorenzo Fontana, explained how they managed to find a reliable way of monitoring Linux system calls. The second one by Kris Nova, shows practical use cases of k8s threat detection against real attacks.

    At the end of the first day of talks, Daniel Stenberg (curl’s developer) gave one of the most important lectures of this Fosdem, titled HTTP/3 for everyone. This talk is in my opinion largely enough to answer every question developers might have about HTTP/3 and QUIC, except maybe for “when will it release?”.

    The main ULB amphitheater

    On Sunday, Ecaterina Moraru came to talk about UI and UX. Her talks contain great and easily applicable tips for developers to build more accessible applications. I feel like this is an extremely important talk since too many open source projects focus on being technically perfect while forgetting that they need to be usable first.

    Last but not least, in the Go room, Derek Parker presented the state of Delve. For those who don’t know it already, Delve is a debugger for Go, usable from the command line or with integrations in Vim, Emacs, IntelliJ… This talk explains Delve’s support for “deterministic debugging” through Mozilla RR (Record and Replay Framework) which is a feature allowing you to capture and replay a bug until you fix it.


    I sadly can’t make an exhaustive list of all the great talks that I might have missed at Fosdem this year. Hopefully, I will be able to see talks of the same quality next year. As usual, I thank all the Fosdem organizers and the ULB for their amazing work and allowing this event to happen for free.

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