/usr/lib/arc/libdmcacix.apd is in nordugrid-arc-plugins-needed 5.0.5-1ubuntu1.
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 | name="acix"
kind="HED:DMC"
description="ARC Cache Index"
version="0"
priority="128"
|