Disk space alerts to your phone.

The problem

A full disk kills databases, stops log rotation, and breaks deployments. Most admins find out when something else fails. A simple cron job that checks df and sends a Nerve signal catches it before the cascade.

Simple threshold check (one disk)

#!/bin/bash
# /usr/local/bin/nerve-disk-check.sh
export NERVE_DSN="nerve://TOKEN:[email protected]"
THRESHOLD=90

USAGE=$(df / --output=pcent | tail -1 | tr -d ' %')
if [ "$USAGE" -ge "$THRESHOLD" ]; then
  echo "DISK ALERT: / is ${USAGE}% full on $(hostname)" | nerve send --severity critical
fi

# Cron: check every 15 minutes
*/15 * * * * /usr/local/bin/nerve-disk-check.sh

All partitions

Loop over all mounted filesystems and alert on any that exceed the threshold.

#!/bin/bash
export NERVE_DSN="nerve://TOKEN:[email protected]"
THRESHOLD=90

df -h --output=target,pcent -x tmpfs -x devtmpfs | tail -n +2 | while read -r mount pct; do
  usage="${pct%%%}"
  if [ "$usage" -ge "$THRESHOLD" ]; then
    echo "DISK: $mount is ${usage}% on $(hostname)" | nerve send --severity critical
  fi
done

With cooldown (avoid spam)

Only alert once per hour per mount point.

#!/bin/bash
export NERVE_DSN="nerve://TOKEN:[email protected]"
THRESHOLD=90
COOLDOWN_DIR="/tmp/nerve-disk-cooldown"
COOLDOWN_MINUTES=60
mkdir -p "$COOLDOWN_DIR"

df -h --output=target,pcent -x tmpfs -x devtmpfs | tail -n +2 | while read -r mount pct; do
  usage="${pct%%%}"
  if [ "$usage" -ge "$THRESHOLD" ]; then
    LOCK="$COOLDOWN_DIR/$(echo "$mount" | tr '/' '_')"
    if [ ! -f "$LOCK" ] || [ $(( $(date +%s) - $(stat -c %Y "$LOCK") )) -gt $(( COOLDOWN_MINUTES * 60 )) ]; then
      echo "DISK: $mount is ${usage}% on $(hostname)" | nerve send --severity critical
      touch "$LOCK"
    fi
  fi
done

Inode exhaustion

A disk can have free space but zero free inodes. This silently breaks writes.

INODE_USAGE=$(df -i / --output=ipcent | tail -1 | tr -d ' %')
if [ "$INODE_USAGE" -ge 90 ]; then
  echo "INODE ALERT: / is ${INODE_USAGE}% inodes on $(hostname)" | nerve send --severity critical
fi

Docker volume check

# /var/lib/docker often fills up silently
DOCKER_USAGE=$(df /var/lib/docker --output=pcent 2>/dev/null | tail -1 | tr -d ' %')
if [ -n "$DOCKER_USAGE" ] && [ "$DOCKER_USAGE" -ge 85 ]; then
  echo "Docker storage ${DOCKER_USAGE}% on $(hostname)" | nerve send --severity alert
fi

Quick start

go install github.com/nerve-ink/nerve-cli/cmd/nerve@latest
export NERVE_DSN="nerve://TOKEN:[email protected]"
echo "DISK: / is 94% full on prod-db-1" | nerve send --severity critical

FAQ