cheap_system_monitor/README.md

Cheap System Monitor

A small Linux system monitor for Ubuntu and Raspberry Pi OS (including the Raspberry Pi 5). It stores metrics in a fixed-size RRD database and produces PNG graphs for the last 3 hours, 1 day, 2 weeks, and 1 year.

It collects:

• processor load averages (1, 5, and 15 minutes)
• CPU user, system, and nice usage
• total network receive/transmit throughput
• disk usage for / and up to two additional mountpoints
• memory usage
• system uptime in days
• CPU temperature and active Raspberry Pi throttling
• failed systemd services and kernel out-of-memory kills
• available filesystem space, inode usage, and read-only filesystem state
• CPU I/O wait
• a combined storage operational-health score from 0 to 10

Install

Python 3 is already included in supported distributions. Install RRDTool, clone/copy this directory, and run the installer:

sudo apt update
sudo apt install rrdtool
sudo ./install.sh

The executable application files are installed under /opt/cheap_system_monitor. Configuration remains in /opt/cheap_system_monitor/monitor.conf, and the RRD database remains under /var/lib/cheap-system-monitor so code, configuration, and mutable data stay separate.

Edit /opt/cheap_system_monitor/monitor.conf to choose network interfaces, mountpoints, and the graph directory. For example, use mountpoints = /, /boot/firmware, /mnt/data to monitor two additional disks; every configured path must be mounted and accessible. Restarting is unnecessary after configuration changes—the next timer runs use the new values. If the RRD has already been created, do not change the order of mountpoints unless you intentionally want the historical graph labels to refer to different disks.

The generated PNG files and four responsive, auto-refreshing dashboard pages are placed in /var/www/html/system-monitor by default. index.html shows the last 3 hours and links to the 1-day, 2-week, and 1-year pages. With a web server installed, such as nginx or Apache, they can be served directly; otherwise they can simply be opened or copied as PNG files.

Check operation

systemctl list-timers 'cheap-system-monitor*'
journalctl -u cheap-system-monitor.service -n 20
rrdtool info /var/lib/cheap-system-monitor/system.rrd

Run either job manually with:

sudo systemctl start cheap-system-monitor.service
sudo systemctl start cheap-system-monitor-graphs.service

The first meaningful network rate appears after two collection samples. A new installation naturally needs time to accumulate history; RRD archives are consolidated to five-minute samples for two weeks and hourly samples for a year.

The RRD schema is fixed when the database is created. When upgrading from a version without the latest monitoring data sources, move or remove the existing system.rrd before the next collection if preserving its old history is not required. The collector will then create a database with the new data sources. Temperature is read from Linux thermal zones. Active Raspberry Pi throttling is read with vcgencmd; it appears as unknown on other systems. Failed services are counted with systemctl. OOM kills come from the kernel's cumulative /proc/vmstat counter and are graphed as events per minute. Available space, inode consumption, and read-only state are retained as inputs to the per-mountpoint health score rather than displayed as separate graphs. I/O wait is included in the CPU graph. These portable indicators work with SD cards and USB drives without requiring SMART support.

The storage operational-health graph shows one score for each configured mountpoint. A score of 10 means no current problem is visible, while a read-only filesystem scores 0. Space and inode usage begin reducing that filesystem's score above 75%; either reaches 0 when exhausted. Host-wide I/O wait above 10% can subtract up to three points from every score because Linux's CPU wait metric cannot attribute the delay to one mountpoint. This is an operational-risk score, not a measurement of flash wear or remaining media life; SD cards and many USB bridges do not expose the hardware data needed to estimate those reliably.

Run from the source tree

For development or a non-system installation, copy the example configuration, change its paths to writable locations, then use:

cp cheap-system-monitor.conf.example cheap-system-monitor.conf
python3 system_monitor.py --config cheap-system-monitor.conf
python3 generate_graphs.py --config cheap-system-monitor.conf