/usr/lib/tmpfiles.d/dbus.conf is in dbus 1.12.2-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | # Fields: type; path; mode; uid; gid; age; argument (symlink target)
# Make ${localstatedir}/lib/dbus/machine-id a symlink to /etc/machine-id
# if it does not already exist
L /var/lib/dbus/machine-id - - - - /etc/machine-id
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