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LXC/LXD containers

Table of contents​

  1. Introduction to system containers
  2. Installing LXD
  3. Container management
  4. Images and profiles
  5. Network and storage
  6. Practical exercises

1 - Introduction to system containers​

LXC vs Docker​

AspectLXC/LXDDocker
TypeFull system containerApplication container
Initsystemd/initPID 1 = application
ServicesMultipleSingle (ideally)
UsageLightweight VMMicroservices
ImagesFull OSesApplication layers

LXC/LXD use cases​

  • Isolated development environments
  • Migration from VMs
  • Multi-distribution testing
  • Isolating traditional services

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2 - Installing LXD​

# Ubuntu/Debian avec snap
snap install lxd

# Ajouter l'utilisateur au groupe
usermod -aG lxd $USER
newgrp lxd

Initialization​

# Configuration interactive
lxd init

# Réponses typiques:
# - Clustering: no
# - Storage backend: dir (ou zfs, btrfs)
# - Network: yes, default bridge
# - Remote access: no
# - Auto-update images: yes

Automatic configuration​

# Configuration via preseed
cat <<EOF | lxd init --preseed
config: {}
networks:
- config:
    ipv4.address: 10.10.10.1/24
    ipv4.nat: "true"
    ipv6.address: none
  description: ""
  name: lxdbr0
  type: bridge
storage_pools:
- config: {}
  description: ""
  name: default
  driver: dir
profiles:
- config: {}
  description: ""
  devices:
    eth0:
      name: eth0
      network: lxdbr0
      type: nic
    root:
      path: /
      pool: default
      type: disk
  name: default
EOF

Verification​

# Statut
lxc version
lxd --version

# Info système
lxc info

# Lister les conteneurs
lxc list

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3 - Container management​

Create and launch​

# Créer et démarrer
lxc launch ubuntu:22.04 mycontainer

# Créer sans démarrer
lxc init ubuntu:22.04 mycontainer

# Depuis une image spécifique
lxc launch images:debian/12 debian-container
lxc launch images:alpine/3.18 alpine-container

Basic commands​

# Lister
lxc list
lxc list --columns "ns46tS"

# Démarrer/Arrêter
lxc start mycontainer
lxc stop mycontainer
lxc restart mycontainer

# Forcer l'arrêt
lxc stop mycontainer --force

# Supprimer
lxc delete mycontainer
lxc delete mycontainer --force  # Si running

Accessing containers​

# Shell interactif
lxc exec mycontainer -- bash
lxc exec mycontainer -- /bin/sh

# Exécuter une commande
lxc exec mycontainer -- apt update
lxc exec mycontainer -- cat /etc/os-release

# En tant qu'utilisateur spécifique
lxc exec mycontainer -- su - username

File transfer​

# Push (local → conteneur)
lxc file push local-file.txt mycontainer/root/

# Pull (conteneur → local)
lxc file pull mycontainer/etc/passwd ./

# Éditer directement
lxc file edit mycontainer/etc/hosts

Information​

# Infos détaillées
lxc info mycontainer

# Configuration
lxc config show mycontainer

# Ressources utilisées
lxc info mycontainer --resources

Snapshots​

# Créer
lxc snapshot mycontainer snap1

# Lister
lxc info mycontainer  # Section Snapshots

# Restaurer
lxc restore mycontainer snap1

# Supprimer
lxc delete mycontainer/snap1

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4 - Images and profiles​

Image management​

# Lister les images locales
lxc image list

# Chercher des images distantes
lxc image list images: debian
lxc image list ubuntu:

# Télécharger une image
lxc image copy ubuntu:22.04 local: --alias ubuntu22

# Infos sur une image
lxc image info ubuntu22

# Supprimer
lxc image delete ubuntu22

# Créer une image depuis un conteneur
lxc publish mycontainer --alias my-custom-image

Image servers​

ServerURLContent
ubuntu:cloud-images.ubuntu.comOfficial Ubuntu
images:images.linuxcontainers.orgMulti-distros

Profiles​

# Lister les profils
lxc profile list

# Voir un profil
lxc profile show default

# Créer un profil
lxc profile create myprofile

# Éditer
lxc profile edit myprofile

# Appliquer à un conteneur
lxc profile add mycontainer myprofile
lxc launch ubuntu:22.04 myc --profile default --profile myprofile

Profile example​

# lxc profile edit myprofile
config:
  limits.cpu: "2"
  limits.memory: 2GB
description: Profil avec limites CPU et RAM
devices:
  root:
    path: /
    pool: default
    size: 10GB
    type: disk
  eth0:
    name: eth0
    network: lxdbr0
    type: nic
name: myprofile

Resource limits​

# CPU
lxc config set mycontainer limits.cpu 2

# Mémoire
lxc config set mycontainer limits.memory 2GB

# Disque (avec profile ou device)
lxc config device set mycontainer root size=20GB

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5 - Network and storage​

Networks​

# Lister les réseaux
lxc network list

# Créer un réseau bridge
lxc network create mybr0 ipv4.address=10.20.30.1/24 ipv4.nat=true

# Attacher à un conteneur
lxc network attach mybr0 mycontainer eth1

# Configuration du conteneur
lxc config device add mycontainer eth1 nic network=mybr0

Static IP​

# Via config
lxc config device override mycontainer eth0 ipv4.address=10.10.10.100

# Ou dans le conteneur
lxc exec mycontainer -- bash
# Configurer via netplan ou /etc/network/interfaces

Storage pools​

# Lister les pools
lxc storage list

# Créer un pool ZFS
lxc storage create mypool zfs

# Créer un pool dir
lxc storage create dirpool dir source=/data/lxd

# Utiliser le pool
lxc launch ubuntu:22.04 myc --storage mypool

Storage volumes​

# Créer un volume
lxc storage volume create default myvolume

# Attacher à un conteneur
lxc config device add mycontainer data disk pool=default source=myvolume path=/data

# Lister
lxc storage volume list default

# Copier un volume
lxc storage volume copy default/myvolume default/myvolume-backup

Mounts from the host​

# Monter un répertoire
lxc config device add mycontainer shared disk source=/home/user/shared path=/shared

# Supprimer le montage
lxc config device remove mycontainer shared

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6 - Practical exercises​

Exercise 1: Web container​

Create an Ubuntu container with Nginx installed:

Solution
# Créer le conteneur
lxc launch ubuntu:22.04 webserver

# Installer nginx
lxc exec webserver -- apt update
lxc exec webserver -- apt install -y nginx

# Vérifier
lxc exec webserver -- systemctl status nginx

# Obtenir l'IP
lxc list webserver

Exercise 2: Resource limits​

Create a container limited to 1 CPU and 512MB of RAM:

Solution
# Méthode 1 : à la création
lxc launch ubuntu:22.04 limited -c limits.cpu=1 -c limits.memory=512MB

# Méthode 2 : après création
lxc launch ubuntu:22.04 limited
lxc config set limited limits.cpu 1
lxc config set limited limits.memory 512MB

# Vérifier
lxc config show limited

Quiz​

Q1. Which command gives you access to a container's shell?

Answer

lxc exec nom-conteneur -- bash

Q2. What is the main difference between LXC and Docker?

Answer

LXC provides full system containers (like lightweight VMs with init), whereas Docker provides application containers (one process per container).

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Key takeaways​

  • LXC/LXD = system containers (lightweight VMs)
  • lxc launch image nom to create a container
  • lxc exec to run commands
  • Profiles to reuse configurations
  • limits.cpu and limits.memory for resources
  • Snapshots to save the state
  • Volumes for persistent storage

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