Install alertmanager

gistfile1.txt

# Create user
useradd --no-create-home --shell /bin/false alertmanager

# Download and unpack
wget https://github.com/prometheus/alertmanager/releases/download/v0.20.0/alertmanager-0.20.0.linux-amd64.tar.gz
tar -xvf alertmanager-0.20.0.linux-amd64.tar.gz
mv alertmanager-0.20.0.linux-amd64/alertmanager /usr/local/bin/
mv alertmanager-0.20.0.linux-amd64/amtool /usr/local/bin/

chown alertmanager:alertmanager /usr/local/bin/alertmanager
chown alertmanager:alertmanager /usr/local/bin/amtool

# Cleanup
rm -rf alertmanager-0.20.0*

# Create configuration file
mkdir /etc/alertmanager
nano /etc/alertmanager/alertmanager.yml

### Configuration
global:
  slack_api_url: 'https://hooks.slack.com/services/x/xx/xxx'

route:
  group_by: ['instance', 'alert']
  group_wait: 30s
  receiver: default-interval
  
receivers:
  - name: 'default-receiver'
    slack_configs:
      - channel: 'alerts'
      
# Change ownership
chown alertmanager:alertmanager -R /etc/alertmanager

# Create systemd unit file
nano /etc/systemd/system/alertmanager.service

### Alertmanager systemd 
[Unit]
Description=Alertmanager
Wants=network-online.target
After=network-online.target

[Service]
User=alertmanager
Group=alertmanager
Type=simple
WorkingDirectory=/etc/alertmanager/
ExecStart=/usr/local/bin/alertmanager --config.file=/etc/alertmanager/alertmanager.yml --web.external-url http://0.0.0.0:9093

[Install]
WantedBy=multi-user.target

# Run service
systemctl daemon-reload
systemctl restart alertmanager