You can sometimes do something like this by editing the hosts file on your system. Steps for windows if your domain was called "foobar.com".
- get the IP address of your domain at dreamhost.
Default Server: merry.christmas
Default Server: ns2.dreamhost.com
The returned IP address for your domain "foobar.com" at dreamhost is "18.104.22.168".
Note that the nameservers at dreamhost seem to be pretty flaky and often return errors. If ns2 doesn't work, try again and again or change the lserver to ns1 or ns3.
- open the hosts file to edit it. On Windows XP this is found by default at: c:\windows\system32\drivers\etc\hosts
Open it in notepad and then add the following lines to the end of the file...
e.g. for the previous domain example it would be:
Save and close the file. You should then be able to access the new site hosted at dreamhost using the domain name "foobar.com".
Note that this will prevent you from accessing the current "foobar.com" at the current host. You will need to comment out or delete those lines from the hosts file to see it again.
Note that you should also delete those lines once it is available via the normal DNS system, otherwise Murphy's Law ensures that something will happen which will make you wish that you did.
Also note that if your site never actually references it's own domain name (i.e. there are no links to foobar.com, just to relative paths like / or /pr0n) then you may be able to add the entries in the hosts with a madeup name and access both sites simultaneously. e.g.
In any case, there is no guarantees that this will actually work. It does for me though.