fprintd

View documentation for listing enrolled fingerprints

$ tldr fprintd-list

$ tldr fprintd-enroll

$ tldr fprintd-verify

$ tldr fprintd-delete

fprintd [OPTION…]

--daemon
    Run as a daemon (default for systemd)

--replace
    Replace any currently running daemon

--debug
    Enable verbose debug logging

--version
    Print version information and exit

--help
    Display help message and exit

-D
    Run as user daemon (session mode)

--user-daemon
    Alternative to -D for user session daemon

fprintd is a background service that provides access to fingerprint readers on Linux systems via D-Bus. It abstracts hardware-specific details, offering a stable API for applications to enroll, verify, and identify users based on fingerprints. Integrated with desktop environments like GNOME and authentication systems via PAM, it enables passwordless login and sudo authentication.

Key features include support for multiple fingerprint readers through libfprint, storage of minutiae templates (not raw images) in ~/.local/share/fprintd for users or /var/lib/fprint for system-wide, and enrollment of multiple fingers per user. It handles device discovery, image processing, and verification stages. Security is enhanced by not storing raw biometric data, using mathematical representations instead.

Commonly started by systemd user services or system-wide, fprintd listens on D-Bus for client requests from tools like fprintd-enroll and fprintd-verify. It's widely used in Fedora, Ubuntu, and other distros for biometric auth.

Requires libfprint-supported hardware; not all scanners work. Biometric data privacy risks; templates stored unencrypted by default. May conflict with multiple daemon instances.

User fingerprints: ~/.local/share/fprintd/<user>/<device>
System-wide: /var/lib/fprint/<user>

Configure via /etc/pam.d/ files using pam_fprintd module for auth.

Developed as part of the fprint project starting 2007 by Richard Hughes. fprintd introduced around 2010 as glib/D-Bus daemon replacing older tools. Merged into systemd user services in recent distros; active maintenance via libfprint v1.x.

fprintd-enroll(1), fprintd-verify(1), fprintd-delete(1), pam_fprintd(8), fprintd(5)