/etc/default/munin-node is in debian-edu-config 1.818+deb8u2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | #Debian Edu is using an alternative configuration file:
DAEMON_ARGS="--config /etc/munin/debian-edu-munin-node.conf"
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