How to setup sub-domains like blogspot

Question

What should do to setup a sub-domain for the users when they sign-up into my site.

What are the infrastructure required? I am using Linux servers.

Answer 1

You can either use a specific DNS (CNAME or A/AAAA) entry for each known subdomain, or a wild-card DNS entry that'll accept *.example.com:

$ORIGIN example.com
foo     IN A 12.34.6.78
bar     IN A 12.34.6.78

or

$ORIGIN example.com
*       IN A 12.34.6.78

The advantage of this latter is that no changes are required to either DNS or Apache configuration once the service is running. The disadvantage is that all such wildcard lookups must (by definition) end up returning the same IP address.

The Apache configuration will depend on your requirements, both for end-user control and security. Note that if the users have permission to run CGI scripts on the server then additional setup will be needed to ensure that that's done securely.

Depending on whether content is static or dynamic this will also affect your configuration:

1. Use mod_vhost_alias to map individual virtual hosts into their individual directories on the server.

2. If you really want, create a separate section for each known site, but then you'll have to restart Apache each time a new user signs up

3. Use a single and then look at the hostname part of the requested URL (from the $SERVER_NAME environment variable) in the scripts that render the output to figure out which user's content to display.