title: Alert Manager won't start but Prometheus starts fine
body: <p>I am trying to start prometheus and alert manager using docker.</p>
  
  <p>However, when running docker-compose up I hit this error:</p>
  
  <pre><code>msg="Loading configuration file failed" 
  file=/etc/alertmanager/alertmanager.yml err="open 
  /etc/alertmanager/alertmanager.yml: no such file or directory"
  </code></pre>
  
  <p>docker-compose.yaml:</p>
  
  <pre><code>version: '2'
  
  services:
  
  prometheus:
      image: prom/prometheus
      privileged: true
      volumes:
          - ./prometheus:/etc/prometheus/
          - ./alertmanager:/alert.rules
      command:
          - --config.file=/etc/prometheus/prometheus.yml
      ports:
          - '9090:9090'
  
  node-exporter:
      image: prom/node-exporter
      ports:
          - '9100:9100'
  
  alertmanager:
      image: prom/alertmanager
      privileged: true
      volumes:
           - ./alertmanager:/etc/alertmanager/
      command:
          - --config.file=/etc/alertmanager/alertmanager.yml
      ports:
          - '9093:9093'
  </code></pre>
  
  <p>alertmanager.yaml</p>
  
  <pre><code>global:
  slack_api_url: 'https://hooks.slack.com/services/eufiwbhfgvehjvfeyvfhevhfvey
  
  route:
    receiver: 'slack'
  
  receivers:
    - name: 'slack'
      slack_configs:
        - send_resolved: true
          username: 'alert'
          channel: '#wgeygyhvdwvy'
  </code></pre>
  
  <p>Prometheus and node-exporter both and runs fine, the file structure for Alertmanager matches Prometheus so can't see where I am going wrong</p>