LXD

Before using Docker containers it’s good to know a little about a similar tool. LXD can run containers and also virtual machines with similar commands. It uses LXC to run containers (as Docker did at the beginning) and Qemu-KVM to run virtual machines. To install LXD 4.0 LTS you need snap.

Install LXD 4.0 LTS

sudo snap install --channel 4.0/stable lxd

Now you need to initialize the configuration:

lxd init

You will found the following questions:

  1. Questin: Would you like to use LXD clustering? (yes/no) [default=no]:
    Answer: no
  2. Question: Do you want to configure a new storage pool? (yes/no) [default=yes]:
    Answer: yes
  3. Question: Name of the new storage pool [default=default]
    Answer: default
  4. Question:* Name of the storage backend to use (btrfs, dir, lvm, zfs, ceph) [default=zfs]:
    Answer: zfs
  5. Question: Create a new ZFS pool? (yes/no) [default=yes]:
    Answer: yes
  6. Question: Would you like to use an existing empty block device (e.g. a disk or partition)? (yes/no) [default=no]:
    Answer: no
  7. Question: Size in GB of the new loop device (1GB minimum) [default=25GB]:
    Answer: Choose a suitable size for you depending on how much space you have.
  8. Question: Would you like to connect to a MAAS server? (yes/no) [default=no]:
    Answer: no
  9. Question: Would you like to create a new local network bridge? (yes/no) [default=yes]:
    Answer: yes
  10. Question: What should the new bridge be called? [default=lxdbr0]:
    Answer: lxdbr0
  11. Question: What IPv4 address should be used? (CIDR subnet notation, “auto” or “none”) [default=auto]:
    Answer: auto
  12. Question: What IPv6 address should be used? (CIDR subnet notation, “auto” or “none”) [default=auto]:
    Answer: none
  13. Question: Would you like LXD to be available over the network? (yes/no) [default=no]:
    Answer: no
  14. Question: Would you like stale cached images to be updated automatically? (yes/no) [default=yes]
    Answer: no
  15. Question: Would you like a YAML “lxd init” preseed to be printed? (yes/no) [default=no]:
    Answer: Optional. Type “yes” if you want to see the result of the initialization.

Output:

config:
  images.auto_update_interval: "0"
networks:
- config:
    ipv4.address: auto
    ipv6.address: none
  description: ""
  name: lxdbr0
  type: ""
  project: default
storage_pools:
- config:
    size: 25GB
  description: ""
  name: default
  driver: zfs
profiles:
- config: {}
  description: ""
  devices:
    eth0:
      name: eth0
      network: lxdbr0
      type: nic
    root:
      path: /
      pool: default
      type: disk
  name: default
cluster: null

Remote repositories

There are multiple available remote repositories to download base images. For example: https://images.linuxcontainers.org

You can list all of them with the following command:

lxc remote list

Search for images

Pass <reponame>:<keywords> to lxc image list

lxc image list images:ubuntu
# or
lxc image list images:ubuntu focal
# or
lxc image list images:ubuntu 20.04
# or
lxc image list ubuntu:20.04

Show image information

To show information about a specific image use lxc image info with <reponame>:<knownalias>

lxc image info ubuntu:f

Aliases are the names of the images with which you can refer to a specific image. One image can have multiple aliases. The previous command’s output is a valid YAML so you can use yq to process it.

lxc image info ubuntu:focal | yq '.Aliases'

Start Ubuntu 20.04 container

lxc launch ubuntu:20.04 ubuntu-focal

List LXC containers

lxc list

Enter the container

lxc exec ubuntu-focal bash

Then just use exit to quit the container.

Delete the container

lxc delete --force ubuntu-focal

Start Ubuntu 20.04 VM

You can even create a virtual machine instead of container if you have at least LXD 4.0 installed on your machine.

lxc launch --vm ubuntu:20.04 ubuntu-focal-vm

It will not work on all machines, only when Qemu KVM is supported on that machine.