Can't add subdomain on LAMP VM Instance on Google Compute Engine - apache

Question

I'm trying to add the blog.mydomain.com subdomain in Apache on a Google Cloud LAMP VM Instance.
In the /etc/apache2/sites-available folder there are three files: default, default-ssl, and lamp-server. I assumed lamp-server is the file being used, so I copied this file to blog.mydomain.com and edited the contents to be:
<VirtualHost *:80>
ServerName blog.mydomain.com
ServerAlias blog.mydomain.com
ServerAdmin webmaster#localhost
DocumentRoot /var/www/blog.mydomain.com/
<Directory />
Options FollowSymLinks
AllowOverride None
</Directory>
<Directory /var/www/blog.mydomain.com/>
Options Indexes FollowSymLinks MultiViews
AllowOverride All
Order allow,deny
allow from all
</Directory>
ErrorLog ${APACHE_LOG_DIR}/error.log
# Possible values include: debug, info, notice, warn, error, crit,
# alert, emerg.
LogLevel warn
CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>
After saving this new file I did sudo a2ensite blog.mydomain.com and then service apache2 reload. After doing this my main website (www.mydomain.com) went down and only would show a page that says "Error establishing a database connection". This message did not come from my application.
What am I doing wrong?

Answer 1

This doesn't make any sense. If you add blog.mydomain.com by issuing a2ensite which creates virtualhost record in sites-available and in sites-enabled which shouldn't impact your original website unless you changes something.
If there is an entry for www.mydomain.com in the virtualhost and its goes to the right folder, you should not get "Error establishing a database connection" I'm guessing this is a wordpress instance.
Make sure your blog.mydomain.com points to the server ip address. Ping it before adding it to the servers web servers configuration.
Also get rid of these lines from the blog.mydomain.com configuration:
<Directory />
Options FollowSymLinks
AllowOverride None
</Directory>
and restart the web server and load blog.mydomain.com and www.mydomain.com.
The message "Error establishing a database connection" is probably coming from the /var/www/blog.mydomain.com/ directory.