nginx中进行301重定向(301 redirect)是非常容易的。比方说要将www.ashchan.com永久性重定向至ashchan.com，有两种方法：

1.方法A

server {
    server_name ashchan.com www.ashchan.com;

    if ($host != 'ashchan.com' ) {
        rewrite  ^/(.*)$  http://ashchan.com/$1  permanent;
        proxy_set_header Host "ashchan.com";
    }
    ...
}

2.方法B(为带www的域名单独设一条server规则)

server {
    server_name  www.ashchan.com;
    rewrite ^(.*) http://ashchan.com$1 permanent;
}