[CentOS] Replacing Multiple Servers with One

> -----Original Message-----
> From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On
> Behalf Of Vipul Agarwal
> Sent: Wednesday, March 06, 2013 12:14 PM
> To: CentOS mailing list
> Subject: Re: [CentOS] Replacing Multiple Servers with One
> 
> On Wed, Mar 6, 2013 at 4:40 PM, Tim Evans <tkevans at tkevans.com> wrote:
> 
> > We are replacing four servers, running mail, web, ftp, and dns,
> > respectively, with a single server to run all four services.
> >
> > The new server will have a new IP address.
> >
> > It seems fairly straightforward to redirect mail, web, and ftp
> > services to the new server via DNS CNAMES, but I'm not quite sure
> > about how to do the change for the DNS service itself.
> >
> > Is there a need to maintain the old DNS server's IP address during a
> > transition, or longer? Via a virtual IP with the old DNS server's IP
> > address on the new machine, perhaps? Or a second NIC with the old
> > address? Or just have the router redirect incoming DNS requests?
> >
> > Thanks.
> > --
> > Tim Evans                       |   5 Chestnut Court
> > Linux/UNIX Consulting           |   Owings Mills, MD 21117
> > http://www.tkevans.com/         |   443-394-3864
> > tkevans at tkevans.com
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> >
> 
> Hi Tim,
> 
> To migrate the DNS server, ideally the steps as follows,
> 
>    - Provision the new server and setup as the secondary DNS server
>    - Sync the zones
>    - Reduce the TTL of the nameservers
>    - Change the new server to primary
>    - Change the glue DNS records (from domain registrar panel - if
>    applicable)
>    - Let the old server running for few days and monitor for any traffic
> 
> Regards,
> Vipul
> _______________________________________________

Also, if you want to be really safe, you could set the old server to forward
requests to the new one via a redirect in apache, in the mailertable (if
using sendmail), and change the welcome message on old ftp server to use the
new one until DNS propogates.