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How Blincus Works

Blincus ships with a set of templates that follow a set of common conventions.

Convention: cloud-init

Each template uses cloud-init to install a set of packages and create a user matching the user on the host.

- curl
- wget
- openssh-server
plain_text_passwd: 'BLINCUSUSER'
home: /home/BLINCUSUSER
shell: /bin/bash
lock_passwd: True
groups: [adm, cdrom, dip, sudo]

The blincus launch command creates an incus container based on the template configuration. The script replaces the BLINCUS* variables with your user name, your full name, and the first SSH public key it finds in ~/.ssh/.

The basic templates install a few packages and create a user. More complicated templates set up device sharing:

gid: "44"
type: gpu
path: /mnt/.container_pulseaudio_socket
source: /run/user/1000/pulse/native
type: disk
path: /mnt/.container_x11_socket
source: /tmp/.X11-unix/X0
type: disk

and even write more complicated scripts to do things like share the host’s graphical and audio sessions.

A healthy amount of the magic that makes Blincus work comes from these cloud-init configurations.

Convention: Host and instance $USER matching

The templates create a user in the container that matches the user on the host. They also set up id maps that map your host user to your user in the instance, allowing seampless file sharing.

Convention: Templates have matching config in config.ini

The Blincus configuration file is located at ~/.config/blincus/config.ini. It contains a few configuration values for each template.

image = images:ubuntu/jammy/cloud
scripts = ubuntu
image = images:ubuntu/jammy/cloud
scripts = ubuntu

The image value tells Blincus which image to start for each template.

The scripts value tells Blincus which directory to mount in the instance for convenience scripts. Blincus will copy the contents of a matching directory at ~/.config/blincus/scripts into the instance at /opt/scripts. In the above example both the ubuntu and ubuntux templates will create containers that have the contents of ~/.config/blincus/scripts/ubuntu mounted at /opt/scripts inside.

As an added bonus, if there is an script in that folder, the pre-built templates are configured to execute it when the container launches.

Convention: Template Names ending in ‘x’ pass through host X and audio

Template names that end in x like ubuntux or fedorax will pass through the X and pulseaudio sockets from the host.

Configs and Directories

Blincus stores user configurations at ~/.config/blincus.

In that directory is a config.ini file used to set configuration values per template.

There are two directories under ~/.config/blincus. scripts and templates.

The scripts directory contains one or more subdirectories that will be copied into an instance when it’s created. The scripts key in config.ini determines which directory. You can have one directory that’s shared by multiple templates (say all Debian based templates use the same scripts). Or you can make a new scripts directory for each template.

The cloud-init and profiles directories contains Incus configuration templates that are used in the blincus launch command.

profiles are Incus configurations that specify settings for your instance. You can apply one or many profiles to your instances. Blincus takes an opinionated approach, specifying one category of configuration per profile, letting you add them together as needed.

cloud-init files are configurations that specify users, package installation, and other operating system configurations on first boot. The big cloud providers like Azure, AWS, and Google Cloud all use this same method to configure your virtual machines when you launch. Blincus uses cloud-init configurations to create a user in your instances that matches your user on the host and setup SSH configuration.

Collectively, a base image, one or more profiles, and a cloud-init are a template.

templates are defined in ~/.config/blincus/config.ini and look like this:

description = Ubuntu Jammy + cloud
image = images:ubuntu/jammy/cloud
scripts = ubuntu

This template does not specify profiles or cloud-init, so Blincus will use the defaults that are listed at the top of the config.ini:

default_cloud-init = debian
default_container_image = images:ubuntu/mantic/cloud
default_container_profiles = container,idmap
default_home-mounts = Documents,projects
default_scripts = ubuntu
default_vm_image = images:ubuntu/mantic/cloud
default_vm_profiles = idmap,vmkeys

image, cloud-init, plus profiles together define a configuration that meets the conventions listed at the top of this page:

  • cloud-init to create user, assign groups, add SSH keys, install packages
  • profiles to configure properties of the Incus instance
  • image to define the base operating system used to create your instance

Additionally, you can add some other convenient things:

  • home-mounts: a list of folders from $HOME on your host that will be mapped into the instance
  • scripts: a directory containing scripts you commonly use