1. 參考這裡設定第一個網站:
https://blog.johnwu.cc/article/centos-asp-net-core-neginx.html
注意, 文章中有一個錯誤:
/etc/nginx/conf.d/my-website.conf 的第 27 行, 應該是 include /etc/nginx/conf.d/default_proxy_settings;
2.  因為要避開 5000 port, 所以修改第二個網站的 appsettings.json, 讓第二個網站開在 5002 port, 如下.
{
"Logging": {
    "LogLevel": {
     "Default": "Information",
     "Microsoft": "Warning",
     "Microsoft.Hosting.Lifetime": "Information"
    }
},
"Kestrel": {
        "EndPoints": {
                "Http": {
                        "Url": "http://localhost:5002"
                }
        }
},
"AllowedHosts": "*"
}
3. 新增 /etc/nginx/conf.d/my-website2.conf, 要注意
    A. portal2
    B. server localhost:5002
    C. server_name coretest2.bike.idv.tw
    當然 SSL 憑証的檔名也要記得改.
upstream portal2 {
    # localhost:5000 改成 ASP.NET Core 所監聽的 Port
    server localhost:5002;
}
server {
    # 只要是透過這些 Domain 連 HTTP 80 Port,都會轉送封包到 ASP.NET Core
    listen 80;
    # 可透過空白區分,綁定多個 Domain
    server_name coretest2.bike.idv.tw;
    location / {
        proxy_pass http://portal2/;
        include /etc/nginx/conf.d/default_proxy_settings;
    }
}
# 用 HTTPS 必須要有 SSL 憑證,如果沒有要綁定 SSL 可以把下面整段移除
server {
    # 只要是透過這些 Domain 連 HTTPS 443 Port,都會轉送封包到 ASP.NET Core
    listen 443 ssl;
    server_name coretest2.bike.idv.tw;
    ssl_certificate /etc/nginx/ssl/coretest2.bike.idv.tw.crt;
    ssl_certificate_key /etc/nginx/ssl/coretest2.bike.idv.tw.key;
    location / {
        proxy_pass http://portal2/;
        include /etc/nginx/conf.d/default_proxy_settings;
    }
}
改完後就可以用了.
以下是 
https://blog.johnwu.cc/article/centos-asp-net-core-neginx.html 抄過來的一些檔案, 作為備份:
setup-aspnet-core.sh
#!/bin/bash
main() {
    sudo yum -y install epel-release
    sudo yum -y update
    install_nginx
    install_dotnet
    sudo firewall-cmd --add-service=http --permanent
    sudo firewall-cmd --add-service=https --permanent
    sudo firewall-cmd --reload
}
install_nginx() {
    echo "###################################"
    echo "########## Install Nginx ##########"
    echo "###################################"
    sudo yum -y install httpd-tools nginx
    sudo setsebool -P httpd_can_network_connect on
    sudo sed -i 's/^SELINUX=.*/SELINUX=disabled/' /etc/selinux/config
    sudo setenforce 0
    sudo systemctl enable nginx
    sudo systemctl restart nginx
}
install_dotnet() {
    echo "###########################################"
    echo "########## Install .NET Core 2.2 ##########"
    echo "###########################################"
    sudo rpm -Uvh https://packages.microsoft.com/config/rhel/7/packages-microsoft-prod.rpm
    sudo yum -y install aspnetcore-runtime-2.2
}
main "$@"
用以下指令執行:
sudo sh setup-aspnet-core.sh
/etc/systemd/system/my-website.service, (/bin/dotnet 有可能是 
/usr/bin/dotnet)
[Unit]
# Description=<此服務的摘要說明>
Description=MyWebsite
[Service]
# WorkingDirectory=<ASP.NET Core 專案目錄>
WorkingDirectory=/usr/share/my-website
# ExecStart=/bin/dotnet <ASP.NET Core 起始 dll>
ExecStart=/bin/dotnet MyWebsite.dll
# 啟動若失敗,就重啟到成功為止
Restart=always
# 重啟的間隔秒數
RestartSec=10
# 設定環境變數,注入給 ASP.NET Core 用
Environment=ASPNETCORE_ENVIRONMENT=Production
Environment=DOTNET_PRINT_TELEMETRY_MESSAGE=false
[Install]
WantedBy=multi-user.target
服務相關指令:
# 開啟,開機自動啟動服務
systemctl enable my-website.service
# 關閉,開機自動啟動服務
systemctl disable my-website.service
# 啟動服務
systemctl start my-website.service
# 重啟服務
systemctl restart my-website.service
# 停止服務
systemctl stop my-website.service
# 查看服務狀態
systemctl status my-website.service
/etc/nginx/conf.d/default_proxy_settings
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection $http_connection;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-Host $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_cache_bypass $http_upgrade;
/etc/nginx/conf.d/my-website.conf
upstream portal {
    # localhost:5000 改成 ASP.NET Core 所監聽的 Port
    server localhost:5000;
}
server {
    # 只要是透過這些 Domain 連 HTTP 80 Port,都會轉送封包到 ASP.NET Core
    listen 80;
    # 可透過空白區分,綁定多個 Domain
    server_name demo.johnwu.cc example.johnwu.cc;
    location / {
        proxy_pass http://portal/;
        include /etc/nginx/conf.d/default_proxy_settings;
    }
}
# 用 HTTPS 必須要有 SSL 憑證,如果沒有要綁定 SSL 可以把下面整段移除
server {
    # 只要是透過這些 Domain 連 HTTPS 443 Port,都會轉送封包到 ASP.NET Core
    listen 443 ssl;
    server_name demo.johnwu.cc;
    ssl_certificate /etc/nginx/ssl/demo.johnwu.cc_bundle.crt;
    ssl_certificate_key /etc/nginx/ssl/demo.johnwu.cc.key;
    location / {
        proxy_pass http://portal/;
        include /etc/nginx/conf.d/default_proxy_settings;
    }
}
Nginx 重新啟動:
# 檢查 Nginx 的設定是否有誤
nginx -t
# 若沒有錯誤,即可套用
nginx -s reload