/var/lib/collectd/rrd/localhost/dump1090-localhost $ sudo systemctl restart collectd
pi@pi108748:/var/lib/collectd/rrd/localhost/dump1090-localhost $ sudo journalctl --no-pager -u collectd | tail -n40
Dec 25 14:46:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:47:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:48:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:49:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:50:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:51:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:52:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:53:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:54:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:55:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:56:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:57:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:58:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 14:59:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 15:00:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 15:01:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 15:02:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 15:03:48 pi108748 collectd[9477]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>
Dec 25 15:04:10 pi108748 collectd[9477]: Exiting normally.
Dec 25 15:04:10 pi108748 collectd[9477]: collectd: Stopping 5 read threads.
Dec 25 15:04:10 pi108748 systemd[1]: Stopping Statistics collection and monitoring daemon...
Dec 25 15:04:10 pi108748 collectd[9477]: collectd: Stopping 1 write threads.
Dec 25 15:04:10 pi108748 collectd[9477]: rrdtool plugin: Shutting down the queue thread.
Dec 25 15:04:12 pi108748 systemd[1]: collectd.service: Succeeded.
Dec 25 15:04:12 pi108748 systemd[1]: Stopped Statistics collection and monitoring daemon.
Dec 25 15:04:12 pi108748 systemd[1]: Starting Statistics collection and monitoring daemon...
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "syslog" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "rrdtool" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "table" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "interface" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "cpu" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "aggregation" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "match_regex" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "df" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "disk" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: plugin_load: plugin "python" successfully loaded.
Dec 25 15:04:12 pi108748 collectd[2607]: Systemd detected, trying to signal readyness.
Dec 25 15:04:12 pi108748 systemd[1]: Started Statistics collection and monitoring daemon.
Dec 25 15:04:12 pi108748 collectd[2607]: Initialization complete, entering read-loop.
Dec 25 15:04:12 pi108748 collectd[2607]: <urlopen error [Errno 2] No such file or directory: '/usr/share/graphs1090/data-symlink/data/stats.json'>