os

The os plugin reports the host itself. It sends CPU counters, memory, real disks, load average, uptime, network throughput, IPv4 addresses and a short list of known service processes. Turn it on for every machine you run an agent on. It is the plugin that fills in the host's OS details and last-seen time on the system record.

Enable it

Add os to the plugins array.

{
  "plugins": ["os"],
  "os": {
    "refreshInterval": 30000
  }
}

Option	Default	What it does
refreshInterval	30000	Milliseconds between reports. The plugin sends one report at startup, then one per interval.

The plugin always reports under the unique id os and names the service after the machine's hostname. A name or uniqueId in this section has no effect.

What it reports

One payload per interval.

• hostname, platform, type, release, arch.
• cpus is the raw os.cpus() array, with per-core times.
• totalmem and freemem in bytes. available is the memory the kernel can hand out without swapping. On Linux it comes from MemAvailable in /proc/meminfo. On macOS it is free + inactive + speculative + purgeable pages from vm_stat. Elsewhere it falls back to freemem.
• disks lists real drives from df, sorted fullest first. Each entry has device, fstype, mount, total, used, free and pct. The plugin drops pseudo filesystems such as tmpfs, overlay and squashfs, loop devices, and bind-mount duplicates. On macOS it keeps / and /Volumes/*, and reports the Data volume as /.
• network has rxBytes, txBytes, rxRate and txRate in bytes per second. The plugin skips loopback and virtual interfaces such as veth*, docker*, br-* and tun*. The first report has no network field, because a rate needs two samples.
• processes aggregates nginx, php-fpm, mysql/mariadb, postgres, redis and node processes from ps. Each entry has name, count, cpu and mem in bytes. The cpu figure is ps %cpu, which is an average over each process's lifetime.
• loadavg, uptime in seconds, and addresses, the first non-internal IPv4 address per interface.

When it alerts

The server's os case checks cpu > 90 and memory.usedPercent > 90 and would raise a warning for either. The plugin sends neither field, so in practice the os plugin never raises an alert.

Every os report still updates the system record. It writes os (platform, release, arch), ip_address, last_seen and status.

On the dashboard

The card is a bar card titled with the hostname, labelled OS · <platform>.

Reading	How it is computed	Warn	Crit
CPU bar	1 - idle / total summed over cpus[].times	above 70%	above 85%
Memory bar	(totalmem - available) / totalmem	above 78%	above 85%
DISK	fullest entry in disks	80% or more	90% or more
LOAD	5-minute load average divided by core count	1.0 per core	2.0 per core
NET	rxRate + txRate	none	none
UPTIME	uptime in hours	none	none

CPU, memory and disk pressure raise the card's color and status word. That is display only. It does not change the stored status and does not send a notification.

A host that has not reported for 300 seconds shows OFFLINE with the time since its last report.

Requirements

• ps and df on the PATH.
• Linux reads /proc/meminfo and /proc/net/dev. macOS runs vm_stat and netstat -ibn.
• No root access needed.

Gotchas

• On platforms other than Linux and macOS, network throughput is omitted rather than shown as zero.
• The CPU figure comes from cumulative os.cpus() counters, which count from boot.