ポートの変更

/etc/apache2/sites-available/ports.confを以下のように編集.

...
Listen 40980
...

/etc/apache2/sites-available/siteA.confを以下のように編集

...
<VirtualHost *:40980>
        ServerAdmin webmaster@localhost
        ServerName ***.***
        ServerAlias ***.***.***
        DocumentRoot /var/www/***
</VirtualHost>
...

Apacheを再起動.

# systemctl reload apache2.service

ファイアウォールを許可.

# ufw allow 40980
# ufw status
Status: active

To                         Action      From
--                         ------      ----
Apache                     ALLOW       Anywhere
OpenSSH                    ALLOW       Anywhere
40980                      ALLOW       Anywhere
Apache (v6)                ALLOW       Anywhere (v6)
OpenSSH (v6)               ALLOW       Anywhere (v6)
40980 (v6)                 ALLOW       Anywhere (v6)