Both pam_usb.so and pamusb-agent use the syslog facility to log authentication
This can be useful for GUI-driven applications (for instance GDM) where you
don't get to see console output.
Messages are logged with the AUTH facility, they are usually written to
/var/log/auth.log but may vary
depending on the operating system you're using.
# tail -f /var/log/auth.log
pamusb-agent: Device "sandisk" has been inserted. Performing
pamusb-agent: Executing "/usr/bin/pamusb-check --quiet
--config=/etc/pamusb.conf --service=pamusb-agent scox"
pam_usb: Authentication request for user "scox" (pamusb-agent)
pam_usb: Device "sandisk" is connected (good).
pam_usb: Access granted.
pamusb-agent: Authentication succeeded. Unlocking user "scox"...
Enabling debug messages may help you find out what's wrong.
To enable them, edit /etc/pamusb.conf and set the following option: