They “weight” between VMs and Application Containers (e.g. Docker) - VMs are heavier and Application Containers the lightest. LXC/LXD are the middle ground.

LXD is the CLI/REST API

“Machine containers” - A full operating system containerized.

Can have access to hardware on the containerized OS

VMs reserve memory for a VM on boot. On LXC, they use limits.memory and limits.cpu, by default all on the machine.

You can make clusters of LXD hosts (you can move a container from one host to another)

You can snapshot/restore containers

You can nest LXD (have LXD inside the containerized OS)

They use the LXD daemon host kernel

You can ping between 2 or more containers using their DNS name (which is container-name.lxd)

On Ubuntu:

• sudo systemctl enable lxd
• Add your user account on the lxd group.
• lxd init
• lxc version
• lxc remote list (list remote repositories)
• lxc image list (show local downloaded images)
• lxc image list images: (images on a repository)
• lxc image list images:deb (images on a repository)
• lxc image list images:cent (images on a repository)
• lxc launch ubuntu:20.04 (launch a container)
• lxc list (list containers)
• lxc delete <container>
• lxc stop <container>
• lxc start <container>
• lxc copy <container> <another-container> (create a new container from an existing one)
• lxc move <container> <new-name> (renames a container)
• lxc exec <container> bash (enter the container as root)
• lxc exec <container> su - <username> (enter the container as another user)
• lxc info <container> (info on running container)
• lxc config show <container> (container configuration - shows limits and other info)
• lxc profile list
• lxc profile show default (show the default profile)
• lxc profile copy default new-profile-name (copy default profile)
• lxc launch ubuntu:18.04 <container> --profile <profile-name> (create a new container with a custom profile)

Restrict resources on container - uses cgroups - you can do that on profile or dinamically:

• Dinamically (on running container): lxc config set <container> limits.memory 512MB
• On the profile:
  • lxc profile edit <profile-name>
  • Change config: {} to:

    config:
      limits.memory: 512MB
    

  • Create a new container using the edited profile.

push files from host to the container: lxc file push <file> <container>/<path>

pull files from the container to host: lxc file pull <container>/<path> <file>

snapshot a container: lxc snapshot <container> <snapshot-name> (copies the entire filesystem)

restore container from snapshot: lxc restore <container> <snapshot-name> (copies the entire filesystem - lxc list shows how many snapshots are there for a container)

To use LXD nesting, you must set security.nesting and security.privileged:

• You cannot set that dinamically
• You must stop the container if it is running, then:
  • lxc config set <container> security.privileged true
  • lxc config set <container> security.nesting true
• … or edit the profile:
  • lxc profile edit <profile-name>
  • Change config: {} to:

    config:
      security.privileged: true
      security.nesting: true