simple-login-gui

A minimal GTK graphical login manager for Devuan Excalibur using sysvinit and seatd. Replaces the text console login on tty1 with a simple username/password screen. On logout from the window manager, the login screen reappears automatically. Supports GTK2 and GTK3.

No elogind. No polkit. No ConsoleKit2.

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Requirements

• Devuan Excalibur (sysvinit)
• XLibre (recommended) or Xorg — must have libseat support
• seatd
• GTK 2 or GTK 3

How it works

inittab (tty1)
    └── xlogin-launcher
            ├── starts seatd (if not running)
            ├── starts XLibre/Xorg on :0 with seatd seat management
            └── execs xlogin (GTK login window)
                    └── on successful login: forks, drops privileges,
                        execs ~/.xinitrc as the user on display :0
                        └── on logout: login window reappears

PAM handles authentication. The session runs entirely as the logged-in user with a clean, minimal environment. The X server stays running between logins.

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Installation

Download the release tarball, extract it, and run the installer:

tar -xf simple-login-gui-1.0.1.tar.gz
cd simple-login-gui-1.0.1
sudo bash install.sh

The installer will ask:

1. Which X server you are using (XLibre or Xorg)
2. Which GTK version to use (GTK3 recommended; GTK2 for minimal systems)
3. Which username to configure for graphical login
4. Which session to use (reads /usr/share/xsessions/ — any installed WM or DE appears here)
5. Whether to start the session inside a D-Bus session bus (recommended — enables trash, removable media, and other GVfs-backed features in file managers such as pcmanfm)

It will then:

• Detect your GPU driver and write /etc/xlogin.conf with appropriate X server flags
• Install runtime dependencies
• Build from source, or use a prebuilt binary if one matching your GTK version is present
• Install binaries to /usr/local/bin/
• Install PAM config to /etc/pam.d/xlogin
• Install the sysvinit service file to /etc/init.d/xlogin-launcher
• Enable seatd to start at boot
• Add the configured user to the input and video groups
• Write ~/.xinitrc for the target user and /etc/skel/.xinitrc for future users
• Update /etc/inittab to replace the tty1 getty with xlogin-launcher

Reboot to activate the graphical login screen.

Session detection

The installer reads /usr/share/xsessions/*.desktop to find available sessions. Any properly packaged window manager or desktop environment installs a file there, so the installer works with whatever is on the system — JWM, Openbox, XFCE4, MATE, LXDE, LXQt, i3, and anything else.

Install your preferred WM or DE before running the installer. If no sessions are found, the installer will ask you to enter a session command manually.

D-Bus session

When prompted, choosing yes wraps the session in dbus-run-session, which starts a D-Bus session bus and tears it down cleanly on logout. This is needed for trash, removable media handling, and other GVfs-backed features in file managers such as pcmanfm. Choosing no launches the session directly with no D-Bus bus — suitable for minimal setups that do not need these features.

Prebuilt binaries

If you build both GTK versions ahead of time, the installer will use the matching prebuilt binary without requiring build tools on the target machine:

make both        # builds xlogin-gtk3 and xlogin-gtk2

XLibre

XLibre is not in the standard Devuan apt repositories. Install it from the XLibre Devuan repository before rebooting:

# See https://x11libre.net/ for current repository instructions

The launcher detects XLibre automatically and prefers it over Xorg.

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Uninstall

Run as root from the project directory:

sudo bash uninstall.sh

This will:

• Remove /usr/local/bin/xlogin and /usr/local/bin/xlogin-launcher
• Remove /etc/pam.d/xlogin and /etc/xlogin.conf
• Remove and disable /etc/init.d/xlogin-launcher
• Restore /etc/inittab (removes the xlogin-launcher line, uncomments the tty1 getty)
• Reload inittab with telinit q

User ~/.xinitrc files and /etc/skel/.xinitrc are not removed. Users remain in the input and video groups. To remove a user from those groups:

gpasswd -d <username> input
gpasswd -d <username> video

Reboot to return to the text console login.

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Manual installation

# Install build dependencies (GTK3)
apt-get install -y libgtk-3-dev libpam0g-dev build-essential gcc make

# Or for GTK2
apt-get install -y libgtk2.0-dev libpam0g-dev build-essential gcc make

# Build (defaults to GTK3)
make

# Or explicitly choose a version
make GTK_VERSION=3   # produces xlogin-gtk3
make GTK_VERSION=2   # produces xlogin-gtk2

# Install (installs the chosen version as /usr/local/bin/xlogin)
sudo make install
sudo make install GTK_VERSION=2

# Install the init.d service file and enable seatd
sudo install -m 755 etc_init.d_xlogin-launcher /etc/init.d/xlogin-launcher
sudo LC_ALL=C update-rc.d seatd defaults

Then edit /etc/inittab manually: comment out the tty1 getty line and add:

1:2345:respawn:/usr/local/bin/xlogin-launcher

Write /etc/xlogin.conf (use the second form for nvidia):

# Open-source GPU (AMD, Intel, modesetting)
echo 'XSERVER_FLAGS="-seat seat0 -keeptty -nolisten tcp -ac"' > /etc/xlogin.conf

# nvidia proprietary driver
echo 'XSERVER_FLAGS="-nolisten tcp -ac"' > /etc/xlogin.conf

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Session configuration

The login manager looks for a session script in this order:

1. ~/.xinitrc — user's own session script (preferred)
2. /etc/X11/xinit/xinitrc — system default
3. Common window managers in order: jwm, openbox-session, startxfce4, mate-session
4. xterm — last resort

A minimal ~/.xinitrc:

#!/bin/sh
exec openbox-session

Make it executable:

chmod 755 ~/.xinitrc

To add another user after installation:

sudo usermod -aG input,video <username>
sudo cp /etc/skel/.xinitrc /home/<username>/.xinitrc
sudo chown <username>:<username> /home/<username>/.xinitrc

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Security notes

• Authentication is handled entirely by PAM (/etc/pam.d/xlogin)
• The xlogin binary runs as root (started by inittab), not setuid — PAM requires root to read /etc/shadow, and X must be started before a user is known. This is the same model as traditional display managers (xdm, slim, ldm). The attack surface is physical-only: X is started with -nolisten tcp and the machine must be locally accessible
• Privilege drop follows the correct order: setgid → initgroups → setuid
• The child process environment is fully cleared before privilege drop
• All inherited file descriptors are closed before exec
• X access control is disabled (-ac) — safe for a single-seat local machine
• The binary is built with stack protection, FORTIFY_SOURCE, PIE, and full RELRO

nvidia proprietary driver

The nvidia proprietary DDX driver does not support libseat device management. The installer detects this automatically and writes /etc/xlogin.conf with seatd integration disabled (-seat seat0 -keeptty omitted). seatd continues to run and is available for Wayland compositors started from the user session. Open-source GPU drivers (AMD, Intel, modesetting) use full seatd integration.

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Troubleshooting

Login screen does not appear after reboot

• Check that XLibre or Xorg is installed: command -v Xlibre || command -v Xorg
• Check seatd is running: pgrep seatd
• Check /var/log/syslog for xlogin-launcher errors
• Test the launcher manually from a tty as root: /usr/local/bin/xlogin-launcher

Authentication always fails

• Verify /etc/pam.d/xlogin is installed
• Test PAM directly: pamtester xlogin <username> authenticate
• Ensure the user's password is set: passwd <username>

Window manager does not start after login

• Check ~/.xinitrc exists and is executable (chmod 755 ~/.xinitrc)
• Test it manually: DISPLAY=:0 sh ~/.xinitrc

Keyboard or mouse not working in the session

• Ensure the user is in the input group: groups <username>
• Add if missing: sudo usermod -aG input <username> then log out and back in

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License

GPL-2.0 — see LICENSE