【2026年版】Linuxサーバー監視ツール完全ガイド：Prometheus・Grafana・Netdataの導入と活用

# ワンライナーインストール
curl https://get.netdata.cloud/kickstart.sh > /tmp/netdata-kickstart.sh
sh /tmp/netdata-kickstart.sh --stable-channel

# 設定ファイルの編集
sudo nano /etc/netdata/netdata.conf

[global]
    hostname = my-server
    history = 3996
    update every = 1

[web]
    bind to = 127.0.0.1
    default port = 19999

[plugins]
    proc = yes
    diskspace = yes
    cgroups = yes

server {
    listen 443 ssl;
    server_name monitor.example.com;

    ssl_certificate /etc/letsencrypt/live/monitor.example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/monitor.example.com/privkey.pem;

    auth_basic "Monitoring";
    auth_basic_user_file /etc/nginx/.htpasswd;

    location / {
        proxy_pass http://127.0.0.1:19999;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

# /etc/netdata/health.d/custom.conf
alarm: cpu_high_usage
on: system.cpu
lookup: average -5m unaligned of user,system
units: %
every: 1m
warn: $this > 80
crit: $this > 95
info: CPU使用率が高くなっています
to: sysadmin

# ユーザー作成
sudo useradd --no-create-home --shell /bin/false prometheus

# ダウンロードと配置
wget https://github.com/prometheus/prometheus/releases/download/v2.51.0/prometheus-2.51.0.linux-amd64.tar.gz
tar xzf prometheus-2.51.0.linux-amd64.tar.gz
sudo cp prometheus-2.51.0.linux-amd64/prometheus /usr/local/bin/
sudo cp prometheus-2.51.0.linux-amd64/promtool /usr/local/bin/

# /etc/prometheus/prometheus.yml
global:
  scrape_interval: 15s
  evaluation_interval: 15s

alerting:
  alertmanagers:
    - static_configs:
        - targets:
          - localhost:9093

rule_files:
  - "alerts.yml"

scrape_configs:
  - job_name: 'node'
    static_configs:
      - targets: ['localhost:9100']

  - job_name: 'nginx'
    static_configs:
      - targets: ['localhost:9113']

wget https://github.com/prometheus/node_exporter/releases/download/v1.8.0/node_exporter-1.8.0.linux-amd64.tar.gz
tar xzf node_exporter-1.8.0.linux-amd64.tar.gz
sudo cp node_exporter-1.8.0.linux-amd64/node_exporter /usr/local/bin/

# /etc/systemd/system/prometheus.service
[Unit]
Description=Prometheus
Wants=network-online.target
After=network-online.target

[Service]
User=prometheus
Group=prometheus
Type=simple
ExecStart=/usr/local/bin/prometheus \
    --config.file=/etc/prometheus/prometheus.yml \
    --storage.tsdb.path=/var/lib/prometheus/ \
    --storage.tsdb.retention.time=30d

[Install]
WantedBy=multi-user.target

sudo apt-get install -y apt-transport-https software-properties-common
sudo mkdir -p /etc/apt/keyrings/
wget -q -O - https://apt.grafana.com/gpg.key | gpg --dearmor | sudo tee /etc/apt/keyrings/grafana.gpg > /dev/null
echo "deb [signed-by=/etc/apt/keyrings/grafana.gpg] https://apt.grafana.com stable main" | sudo tee /etc/apt/sources.list.d/grafana.list
sudo apt-get update
sudo apt-get install grafana
sudo systemctl enable --now grafana-server

# /etc/prometheus/alerts.yml
groups:
  - name: server_alerts
    rules:
      - alert: HighCPUUsage
        expr: 100 - (avg by(instance) (rate(node_cpu_seconds_total{mode="idle"}[5m])) * 100) > 85
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "CPU使用率が高い ({{ $labels.instance }})"
          description: "CPU使用率が85%を超えています: {{ $value }}%"

      - alert: HighMemoryUsage
        expr: (1 - (node_memory_MemAvailable_bytes / node_memory_MemTotal_bytes)) * 100 > 85
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "メモリ使用率が高い ({{ $labels.instance }})"

      - alert: DiskSpaceLow
        expr: (1 - (node_filesystem_avail_bytes{fstype!="tmpfs"} / node_filesystem_size_bytes{fstype!="tmpfs"})) * 100 > 85
        for: 10m
        labels:
          severity: critical
        annotations:
          summary: "ディスク容量が残り少ない ({{ $labels.instance }})"