Interesting that for the two nominally identical Raspberry Pi cards, the one running gpsd and the PPS software for "precise" timekeeping uses about 3% CPU, versus about 1% for the Raspberry Pi without and syncing just off the LAN. Monitoring memory can be useful if you think there is a process which is leaking memory, and monitoring CPU will show how near to being saturated your Raspberry Pi is - whether it may be able to handle more work, for example.
Access to this data is a standard part of Linux for the Raspberry Pi, once SNMP has been installed (see below).
As most of my Raspberry Pi cards are used headless - i.e.
without a keyboard or monitor - I wanted to monitor what was happening remotely.
In addition to monitoring the NTP Server operation, I've added general SNMP support (Simple Network Management Protocol) which has allow monitoring of the network I/O, disk space, CPU temperature and, with a little additional hardware, ambient temperature monitoring.
You need to edit the configuration if you want to monitor your Raspberry Pi from across the network rather than just locally.
Note that this data maybe a megabyte or more per day, so think about keeping only a few days worth, and only enabling statistics collection when needed as the number of writes to the SD card flash memory is limited.
To view the results from a Windows PC (so that you can run my NTP Plotter program or use the Meinberg NTP Monitor) you need to install and configure a package called SAMBA, which allows a UNIX file system to be seen by a Windows network client.The following steps are based in information from: If you want write access, replace "read only" with "writeable" as in the second example above.The configuration below allows anyone to read the SNMP data - you may want a more secure configuration.The changes below may not be ideal, but they are what I found to be necessary to get it working: For monitoring with MRTG, you can get the results shown here if you have a remote system running MRTG, with an include script something like this zip archive.You could also install MRTG on the Raspberry Pi itself.I do wonder what other variables you could monitor, as plotting NTP rate of change versus board or chip temperature would be an interesting exercise.