nginx -V 2>&1 | grep -o with-http_stub_status_module
vi /etc/nginx/nginx.conf
location /nginx_status {
stub_status on;
access_log off;
allow 127.0.0.1;
allow your_IP;
deny all;
}
service nginx reload

vi /etc/munin/plugin-conf.d/nginx_
[nginx*]
env.url http://localhost/nginx_status

cd /etc/munin/plugins/
sudo ln -sf /usr/share/munin/plugins/nginx_* .
service munin-node restart