rustguac/docs/vdi.md

VDI Desktop Containers

rustguac can spawn ephemeral Docker desktop containers on demand. Each user gets their own isolated Linux desktop accessible via the browser, with no client software required.

How it works

1. An admin creates a VDI entry in the address book, specifying a Docker image
2. When a user clicks Connect, rustguac creates a Docker container from that image
3. The container runs xrdp on port 3389, and guacd connects to it via RDP
4. The user sees a full Linux desktop in their browser
5. On disconnect (tab close, network drop), the container keeps running for reconnection
6. On logout from the desktop, the container is stopped and removed
7. Idle containers (no active session) are automatically cleaned up after a configurable timeout

Prerequisites

VDI requires Docker on the same machine as rustguac. Install Docker and grant access:

# Install Docker (if not already installed)
curl -fsSL https://get.docker.com | sh

# Allow the rustguac user to manage containers
sudo usermod -aG docker rustguac
sudo systemctl restart rustguac

You also need at least one Docker image with xrdp pre-pulled on the host (see Docker image requirements below).

Configuration

Add a [vdi] section to your config file:

[vdi]
enabled = true
# docker_socket = "/var/run/docker.sock"   # default
# default_cpu_limit = 2.0                   # cores, 0 = no limit
# default_memory_limit = 2048               # MB, 0 = no limit
# ready_timeout_secs = 30                   # wait for xrdp to start
# idle_timeout_mins = 60                    # container lifetime after disconnect
# home_base = "/vdi-homes"                  # persistent home directories
# allowed_images = ["myregistry/desktop:latest"]  # whitelist, empty = allow all

The rustguac system user must be in the docker group:

sudo usermod -aG docker rustguac
sudo systemctl restart rustguac

Docker image requirements

Any Docker image that meets these requirements will work:

• xrdp listening on port 3389 with TLS certificates configured
• Accepts environment variables: VDI_USERNAME, VDI_PASSWORD
• Entrypoint creates the Linux user, sets the password, and starts xrdp

A minimal test image is included at contrib/vdi-test-image/ (Debian + xfce4).

Example entrypoint

#!/bin/bash
set -e
USERNAME="${VDI_USERNAME:-user}"
PASSWORD="${VDI_PASSWORD:-password}"

if ! id "$USERNAME" &>/dev/null; then
    useradd -m -s /bin/bash "$USERNAME"
fi
echo "$USERNAME:$PASSWORD" | chpasswd
echo "xfce4-session" > /home/"$USERNAME"/.xsession
chown "$USERNAME":"$USERNAME" /home/"$USERNAME"/.xsession

# Configure TLS for xrdp
sed -i \
    -e 's|^certificate=.*|certificate=/etc/ssl/certs/ssl-cert-snakeoil.pem|' \
    -e 's|^key_file=.*|key_file=/etc/ssl/private/ssl-cert-snakeoil.key|' \
    /etc/xrdp/xrdp.ini

mkdir -p /run/dbus
dbus-daemon --system --fork 2>/dev/null || true
xrdp-sesman --nodaemon &
exec xrdp --nodaemon

Address book setup

1. Create a folder in the address book (or use an existing one)
2. Add a new entry with type VDI (Docker)
3. Set the Container Image (e.g. rustguac-vdi-test:latest)
4. Optionally set CPU limit, memory limit, environment variables, idle timeout
5. Click Save

Users in the folder's allowed groups can now click Connect to get a desktop.

Container lifecycle

Event	What happens
User clicks Connect	Container created (or reused if already running)
User closes browser tab	Container keeps running
Network drops	Container keeps running (reconnect when back online)
User logs out of desktop	Container stopped and removed
Idle timeout expires	Container stopped and removed by background reaper
Admin terminates session	Session ends, container keeps running

Persistent home directories

Set home_base in the VDI config to enable persistent user data:

[vdi]
home_base = "/vdi-homes"

Each user gets {home_base}/{username} mounted as /home/{username} inside the container. Files persist across container restarts. The directory is created automatically on first use.

Active Sessions

The address book shows an Active Sessions section with thumbnail previews of running sessions. Thumbnails are captured every 10 seconds from the browser display. Click a thumbnail to reconnect.

Dormant VDI containers (running but no active browser session) also appear with their last captured thumbnail.

Per-entry settings

Each VDI address book entry can override:

• CPU limit (cores) — overrides default_cpu_limit
• Memory limit (MB) — overrides default_memory_limit
• Idle timeout (minutes) — overrides idle_timeout_mins
• Environment variables — custom KEY=VALUE pairs passed to the container
• Banner — message shown before session starts

Security notes

• Container images must be pre-pulled on the Docker host (no automatic pull)
• Use allowed_images to restrict which images can be used
• Containers run with default Docker isolation (no --privileged)
• Credentials are auto-generated per session (users never see the RDP password)
• The rustguac user needs Docker socket access but no other elevated permissions