Removing munin-node …
[FAIL] Munin-Node appears to be unconfigured. … failed!
invoke-rc.d: initscript munin-node, action “stop” failed.
dpkg: error processing munin-node (–purge):
subprocess installed pre-removal script returned error exit status 6
[FAIL] Munin-Node appears to be unconfigured. … failed!
invoke-rc.d: initscript munin-node, action “start” failed.
dpkg: error while cleaning up:
subprocess installed post-installation script returned error exit status 6
Errors were encountered while processing:
munin-node
E: Sub-process /usr/bin/dpkg returned an error code (1)

The init.d checks if it’s configured

/etc/init.d/munin-node

elif [ ! -e $CONFFILE ]; then
log_failure_msg “Munin-Node appears to be unconfigured.”
exit 6
fi

Which is what is causing this issue, changing this too,

elif [ ! -e $CONFFILE && $1 != “stop” ]; then
log_failure_msg “Munin-Node appears to be unconfigured.”
exit 6
fi

Should solve the issue.