HDM — HackerOS Display Manager

HDM is a production display manager for Linux, built with:

• Rust daemon (hdm) — manages PAM auth, sessions, VT switching
• Tauri + React greeter (hdm-greeter) — the login UI
• Unix socket IPC — secure daemon↔greeter communication

HDM is a rival to SDDM, GDM, and LightDM, designed for the Blue Environment Wayland desktop but works with any session.

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Features

• 🔐 Real PAM authentication via /etc/shadow + crypt(3)
• 🖼️ Aurora glassmorphism UI — animated background, user avatars
• 🖥️ Session management — Wayland & X11 sessions from .desktop files
• 👥 Multi-user — lists system users (UID ≥ 1000), user avatars from ~/.face
• ⚡ Autologin support with configurable delay
• 🔌 Power menu — shutdown, reboot, suspend, hibernate with countdown
• 🔒 Brute-force protection — 5 attempt limit per session
• 📋 systemd integration — replaces display-manager.service
• 🎨 Wallpaper support — reads /etc/hdm/wallpaper.png

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Architecture

┌─────────────────────────────────────────────────┐
│  TTY1 / VT1                                      │
│                                                   │
│  ┌─────────────────────────────────────────────┐ │
│  │  hdm (daemon, root)                         │ │
│  │    PAM authentication                        │ │
│  │    Session launching (drop privs to user)    │ │
│  │    VT management                             │ │
│  │    IPC: /run/hdm/hdm.sock                 │ │
│  └───────────────┬─────────────────────────────┘ │
│                  │ Unix socket (JSON)             │
│  ┌───────────────▼─────────────────────────────┐ │
│  │  hdm-greeter (Tauri, runs as _hdm user)     │ │
│  │    Solid.js UI (TypeScript + Tailwind)       │ │
│  │    Clock, user list, password input          │ │
│  │    Session picker, power menu                │ │
│  └─────────────────────────────────────────────┘ │
└─────────────────────────────────────────────────┘

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Quick Install

# Clone / extract HDM
cd HDM

# Build and install (requires Rust + Node.js)
sudo bash install.sh

# With autologin:
sudo bash install.sh --autologin myusername

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Manual Build

# Install build dependencies (Debian/Ubuntu)
apt install cargo nodejs npm libpam-dev

# Enable
sudo systemctl enable --now hdm

Rust toolchain requirement: HDM's config parser depends on hk-parser (crates.io, hk-parser = "0.3.2"), which pulls in indexmap 2.14.x → hashbrown 0.17.x, a dependency that declares Rust's 2024 edition. That means building daemon/ and greeter/ now requires Rust 1.85 or newer (rustup update stable if you're on an older toolchain — the rustc/cargo shipped by some LTS distro repos, e.g. Ubuntu 24.04's apt install cargo, is only 1.75 and is too old for this). This is a requirement of the .hk-parsing dependency itself, not something HDM's own code opts into.

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Configuration

Edit /etc/hdm/hdm.hk — HDM's config is in HackerOS's own .hk format, not TOML:

[general]
-> greeter_path   => "/usr/bin/hdm-greeter"
-> vt             => 1
-> theme          => blue
-> show_user_list => true
-> allow_root     => false
-> minimum_uid    => 1000

! Autologin (optional) — uncomment and fill in to enable:
! [autologin]
! -> user    => username
! -> session => blue-environment

[power]
-> shutdown  => "shutdown -h now"
-> reboot    => reboot
-> suspend   => "systemctl suspend"
-> hibernate => "systemctl hibernate"

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User Avatars

HDM reads user avatars from (in priority order):

1. ~/.face
2. ~/.face.icon
3. ~/.config/hdm/avatar.png
4. /var/lib/AccountsService/icons/<username>

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Logs

# View HDM logs
journalctl -u hdm -f

# Or from file
tail -f /var/log/hdm/hdm.log

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安全 notes

Content 安全 Policy. greeter/tauri.conf.json sets a CSP rather than leaving it null. style-src includes 'unsafe-inline' — this is a deliberate, known tradeoff, not an oversight: the greeter UI sets style="..." attributes at runtime throughout (a carry-over from the original Svelte template's inline style bindings, kept for readability of long conditional style strings as template literals rather than large object literals). Runtime-set inline styles aren't covered by Tauri's automatic build-time script/style hashing, so 'unsafe-inline' is required for the UI to render at all under a strict CSP. Everything else (script-src, font-src, default-src) is locked to 'self' with no external origins. If this codebase migrates from string styles to style={{...}} objects or CSS classes/custom properties in the future, 'unsafe-inline' can be dropped from style-src entirely.

Fonts are self-hosted, not loaded from Google's CDN — see ui/src/fonts.css. A login screen has to render before networking is necessarily up (fresh install, wifi still associating, airgapped machines), so HDM ships its fonts (@fontsource/oxanium, @fontsource/dm-sans, @fontsource/jetbrains-mono) as part of the built UI bundle instead of fetching them at runtime.

Authentication rate limiting is enforced server-side, in daemon/src/pam_auth.rs::RateLimiter, keyed by username and shared across every IPC connection — not just in the greeter UI's own countdown display. A client that skips the UI and calls the daemon's IPC commands directly still hits the same lockout.

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Comparison

Feature	HDM	SDDM	GDM	LightDM
Wayland native	✅	✅	✅	⚠️
X11 support	✅	✅	✅	✅
PAM auth	✅	✅	✅	✅
Autologin	✅	✅	✅	✅
Custom themes	✅	✅	❌	✅
User avatars	✅	✅	✅	✅
Blue Environment	✅	❌	❌	❌
Aurora UI	✅	❌	❌	❌
Glassmorphism	✅	❌	❌	❌
Rust backend	✅	✅	❌	❌
Solid.js frontend	✅	❌	❌	❌

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License

GPL-3.0 — © 2026 HackerOS Team