nginxでメンテナンスページを表示させる。 ref: https://qiita.com/kooohei/items/b0deaf39124e7a47546a

maintenance

set $maintenance "true";

if ($uri ~ "^/maintenance.html") {
  set $maintenance "false";
}
if ($uri ~ "^/exclude/") {
  set $maintenance "false";
}
if ($remote_addr ~ "xxx.xxx.xxx.xxx") {
  set $maintenance "false";
}
if ($maintenance = "true") {
  rewrite ^(.*)$ http://www.hoge.jp/maintenance.html? redirect;
}