Load Average Alert Shell Script

When users report “the server is slow,” load average is the first number operators check. This script compares 1-minute load to threshold × CPU cores and emails a short report with a top snapshot when the box is overloaded.

What this script does

Reads load from /proc/loadavg
Sets threshold relative to nproc CPU count
Emails only when load exceeds limit (not every cron tick)
Includes top -bn1 head in the message body
State file prevents alert spam within a cooldown window

Prerequisites

mail or mailx for alerts (or adapt to webhook)
bc or awk for float compare
Readable /proc/loadavg

Step 1: Save the script

sudo nano /usr/local/bin/load-alert.sh
sudo chmod +x /usr/local/bin/load-alert.sh

Step 2: Full script (scroll to read)

load-alert.sh

#!/usr/bin/env bash
set -euo pipefail

ALERT_TO="[email protected]"
THRESHOLD_PER_CPU="${THRESHOLD_PER_CPU:-1.0}"
COOLDOWN_SEC=900
STATE="/var/run/load-alert.last"
LOG="/var/log/load-alert.log"

log(){ echo "[$(date '+%F %T')] $*" | tee -a "$LOG"; }

cpus=$(nproc)
load1=$(awk '{print $1}' /proc/loadavg)
limit=$(awk -v c="$cpus" -v t="$THRESHOLD_PER_CPU" 'BEGIN{printf "%.2f", c*t}')

log "load1=$load1 limit=$limit (${cpus} CPUs)"

awk -v l="$load1" -v m="$limit" 'BEGIN{exit (l>m)?0:1}' || { log "OK under threshold"; exit 0; }

now=$(date +%s)
if [[ -f "$STATE" ]]; then
  last=$(cat "$STATE" 2>/dev/null || echo 0)
  if (( now - last < COOLDOWN_SEC )); then
    log "SKIP alert (cooldown)"
    exit 0
  fi
fi

{
  echo "High load on $(hostname -f)"
  echo "load1=$load1 threshold=$limit CPUs=$cpus"
  echo "--- top ---"
  top -bn1 | head -n 25
} | mail -s "[load] $(hostname -s) load $load1" "$ALERT_TO"

echo "$now" >"$STATE"
log "ALERT sent to $ALERT_TO"

Scroll inside the box to read the full script.

Step 3: Configure settings

Explain load vs CPU%: load average guide
Pair with email on failure wrapper
Swap pressure: swap alert script

Shell script sending alert when Linux load average is high

Step 4: Test manually

THRESHOLD_PER_CPU=0.1 sudo /usr/local/bin/load-alert.sh

cat /var/run/load-alert.last

Schedule with cron

sudo crontab -e

Add:

*/5 * * * * /usr/local/bin/load-alert.sh >> /var/log/load-alert.log 2>&1

Load Average Alert Shell Script for Linux (Email, Threshold, nproc)