Hi, I'm trying to find out how to setup domain mapping via DNS but without success, I was hoping you could give me instructions on how to map a domain through DNS please.

Thanks

DNS and apache (or similar) configuration are 2 differents things.

The DNS is used to convert a domain name by its IP.
When you have configured your DNS, you can use the command
> nslookup YOURDOMAIN.COM
and see if you receive the IP

If yes, this means that the DNS is correctly configured.
If the website is not displayed, you also have to check the "apache" configuration.
In general, the configuration of apache is done via a "Control Panel".
With cPanel/WHM, you have to go in the "addOn Domain" or "Subdomain" the relationship between the domain and it location on the disk (document root).
cPanel also do the DNS update for you.

I could use some help with this, too. I have a slave site for which I want to change the primary domain for. For this post, let's say I have the current domain: legacydomain.com and the newdomain.com.

I added newdomain.com domains to the JMS template for the legacy site alongside the existing legacydomain.com urls.

I also created an AddOn domain called newdomain.com in cPanel and gave it the following path for the Document Root:

/domains/legacydomain/public_html

It set up redirection to newdomain.com/^/site/(.*)$ If I change that redirect to www.legacydomain.com, it still doesn't work.

What do I need to do to get it to display the content of legacydomain.com in newdomain.com?

I can't seem to turn off redirection.

*********** Update: *************

Looks like I was getting a cached version. The changes did work and the legacydomain.com site does display as wanted.

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Is this the best way to handle this, if the client actually no longer wants to use the legacydomain.com url, but rather, to do a 301 permanent redirect from the legacydomain.com url to the newdomain.com url?

It's confusing when working in the JMS environment.

You can NOT used redirection because the redirection change the domain name received by JMS.
The begining was good to just create the Addon Domain for which you give the Document root of the legacay domain.
You just have to update the JMS definition to add the new domain to the definition of the legacy one. So that they will become synonym.

Put the new domain URL as first one in the JMS definition and select "redirect to the first one" radio button.
So that the legacy will be redirected to the first one that is the new domain.