Allow access to PhpMyadmin only on a specified virtualhost

Remove the Alias declaration

Alias /phpmyadmin /usr/share/phpmyadmin

from the server context and put it in the relevant vhost context

<VirtualHost *:80>
    ServerName onlyphpmyadmin.domain.com
    .
    .
    .
    Alias /phpmyadmin /usr/share/phpmyadmin
</VirtualHost>

It may be easier and preferable to just include the whole phpmyadmin config into the relevant vhost

<VirtualHost *:80>
    ServerName onlyphpmyadmin.domain.com
    .
    .
    .
    include /path/to/phpmyadmin.conf
</VirtualHost>

and then remove that include from the server context and restart apache for the changes to take affect.

In RHEL/CentOS, Apache loads /etc/httpd/conf.d/phpmyadmin.conf to set up the /phpmyadmin alias. The Directory directive is also initially set to only allow traffic from localhost, so you may receive a 403 error when accessing phpmyadmin like "domain.com/phpmyadmin".

Using the following, you can set up RHEL/CentOS to only allow the /phpmyadmin alias to work from a specific virtual host.

/etc/httpd/conf.d/phpmyadmin.conf

<Directory "/usr/share/phpmyadmin">
#  Order Deny,Allow
#  Deny from all
   Allow from 127.0.0.1
</Directory>

#Alias /phpmyadmin /usr/share/phpmyadmin
#Alias /phpMyAdmin /usr/share/phpmyadmin
#Alias /mysqladmin /usr/share/phpmyadmin

Next, add the alias directive to your vhost and restart Apache.

Please note, this is not the most secure implementation. Please take care to secure /phpmyadmin through authentication, IP restrictions or a combination of both.