Comment 6 for bug 1484740

Explanation :

The bug is found in debian/trouser.postinst at line :19[1].
It tries to perform a "pidof udevd" on a machine where it is "systemd-udevd".

Because "pidof udevd" return nothing, than the if statement fails.

As mentioned, above by Edmond, changing the from "pidof udevd" to "pidof systemd-udevd" works... but I think the best approach is what is found on Wily/Xenial and Debian upstream which is to use "udevadm --version"[2] instead.

[1] # ask udev to check for new udev rules (and fix device permissions)
==> if [ -x /etc/init.d/udev ] && pidof udevd > /dev/null; then
        udevadm control --reload-rules
        udevadm trigger --sysname-match="tpm[0-9]*"
fi
;;

[2] # ask udev to check for new udev rules (and fix device permissions)
==> if [ -e /dev/tpm0 ] && udevadm --version > /dev/null; then
            udevadm control --reload-rules ||:
            udevadm trigger --sysname-match="tpm[0-9]*" ||:
    fi
    ;;

Eric