Posts tagged ‘domain’

The other day, Klint Finley wrote a very good walkthrough of using the new Multisite functionality of WordPress 3.0. In the comments, a lot of people wanted to know how to use your own domain names. Since I’m doing that now, here’s a quick walkthrough/how-to guide.

Step 1: Manual Plugin Installation

The Domain Mapping plugin is not your regular kind of plugin. You cannot install it through the normal Plugins->Add New menu. Well, actually, you can, it just won’t work.

So first, download the plugin manually.

Note: For this tutorial, I will be using the WordPress MU Domain Mapping plugin. However, I am using the trunk version of the plugin. It has fixes in it that you will need for proper 3.0 support. Don’t try it with the regular version. (Note: The regular version works fine. This was originally written before the latest version, or 3.0, was released.)

The plugin has two main files you need to put in the proper places.

Domain mapping php file location

The first file is the domain_mapping.php file. This needs to go into the mu-plugins folder. The mu-plugins folder is a special folder, which you may not even have yet. Just create it underneath the wp-content folder and put that file into it.

Sunrise php file location

The second file is the sunrise.php file. This is a special filename for WordPress. Don’t worry about it, just put it in the wp-content folder.

Step 2: Activate Sunrise

Now you need to edit your wp-config.php file. Add this line of code to it:

define( 'SUNRISE', 'on' );

Simple, really. This will cause WordPress to go load that sunrise.php file and use it.

Step 3: Server info

Now you have to configure the domain mapping plugin so that it knows what it’s doing properly. This is easy to do, really. Go to your main domain’s admin page and log in as a super admin. Then go to the new Super Admin->Domain Mapping menu.

Domain mapping setup screen

Here you have a few different options, but two main ones that count. You can either put in the IP address of your server (as defined in your domain’s main A record) or you can put in a CNAME that points to your server. The IP address is what most people will want to use. If your server uses more than one, you can enter them all here, separated by commas.

Other options on this page:

  • Remote Login – This will make your login pages for all sites redirect to your main site to do the actual login. The benefit of this is that when you log in to one, you log into all of them. The downside is that the URL changes to another domain in order to log in.
  • Permanent redirect (better for your blogger’s pagerank) – This makes your subdomain or subdirectory sites redirect to their domains. You should leave this on.
  • User domain mapping page – Turn this on if you want users to be able to put in their own domains for mapping.
  • Redirect administration pages to blog’s original domain (remote login disabled if redirect disabled) – This makes all admin pages show up on the original domain instead of on the new domains. You need this enabled for remote login to work.

Generally I leave only the middle two on. Remote-login is iffy at best, and I want my new domain name to show up everywhere.

Step 4: Mapping the Domain

There’s a bit of a prerequisite here before you do this. When you buy a new domain, you will need to edit its DNS settings to actually point to your server IP or CNAME or whatever you do to make the domain connect to your server. For me, I just give it a new A record with my server IP in it. Easy.

Update: Okay, so there may be more to it than just that, depending on your host. Every host is different, and you’ll have to talk to your host to make them able to point the domain name at your existing site. How to do this varies from host to host, but the important thing is that when you visit your new domain (before you do this!) then you want it to go to your main site, as is.

There’s two ways you can actually map a domain to one of your sites. The user screen is the simplest way, if you left that option on before. Log into the site you actually want to map to a new domain, then go to Tools->Domain Mapping.

User Domain Mapping Screen

All you really do is put in a new domain and set it as the primary. Simple.

Note that if you didn’t get the domain pointed at your server before doing this, then your site will instantly vanish from the realm of mortal man. Setting the primary domain takes effect instantly. You won’t be able to access the site through the old domain any more.

The other way to set domain mapping is through the Super Admin->Domains menu. Here you’ll find a list of sites and their ID numbers. You can map an id number directly to a domain name here. The Tools approach is a bit easier to use, but this will allow you to map domains without visiting them, as you can access this list from your main domain. You can also correct broken domain mappings from here.

Step 5: Seeing the Mapped Domains

If you go to Super Admin->Sites, you’ll find this type of a listing:

Sites listing

You’ll note that on the right hand side you can see the column showing the mapped domains.

Special Note: See in the picture how I’m using a subdirectory install? That’s relatively new. In older versions of the domain mapping system, you had to use a subdomain installation and wildcard DNS for domain mapping to work. This is no longer the case, domain mapping works just fine with subdirectories.

Conclusion

And that’s how it’s done. It’s not super complex, but it does require some knowledge of DNS and how servers work. If you can successfully set up a multi-site install to begin with, you can probably do this as well. Just be aware that it is slightly finicky, and know that you will break your site if you put in the wrong settings somewhere. However, your main domain will always be accessible as long as you don’t try to map it, so you’ll be able to go in from there to correct your mistakes.

Shortlink:

Recently, a site I frequent went down for an extended period. I waited patiently for it to return (it said it was upgrading). A week later, I hopped on Twitter and asked the author WTF? I learn that the site has been back up for days. Only I, and probably half of the internet, had no idea. Why? DNS. Done wrong, it’s a bitch.

I think there’s an object lesson here.

So, let’s say that you’ve decided that your webhost sucks rocks, and you want to change hosts for your domain from your existing server called junkhost to a much better and new fangled one called goodrack.

How To Do DNS The Wrong Way

(or why the site is currently totally missing from the internet as I see it)

Step 1: Your domain’s nameservers are currently set to dns1.junkhost.com and dns2.junkhost.com.

Step 2: Your new hosting company tells you to set them to dns1.goodrack.com and dns2.goodrack.com. You do so.

Step 3: You wait a day or two or possibly flush your home router’s DNS and voila, your host is now visible to you.

Why this is the wrong way: DNS is a caching system. When I try to lookup the IP address for yoursite, then I don’t ask your nameserver for it. I ask my nameserver for it. My nameserver then asks you, but only if it doesn’t already know.

See, you communicate with your site regularly. So you are doing lots of queries and flushing the DNS on a regular basis. Home router DNS systems tend to flush a lot, as do cable modems and cable companies, etc. So you might see that nameserver switch in just a day or so. Maybe less.

Me, on the other hand, am sitting here at BigCompany, which has weird fiber and satellite links to all sorts of places. If my DNS has your nameservers cached, it could be cached for weeks. And you don’t have a whole hell of a lot of control over what is called “TTL”, or “Time-To-Live”.

Time-To-Live is what tells DNS caching servers when to drop the info and get fresh data. If the TTL for, say, a normal DNS lookup is 2 hours, then my nameserver isn’t constantly querying yours whenever I look at your site. It only queries it once every two hours, tops. More or less.

Sitting here looking at the thing in debug mode, I see that there’s another 46 hours left to go before the old data I now know exists gets flushed out of the DNS server. By then, I won’t have been able to access his site for a bit under 2 weeks. And I’m not the only one.

How To Do DNS The Right Way

(or why I can change hosts in under a couple hours)

Step 1: My domain’s nameservers are currently set to dns1.myregistrar.com and dns2.myregistrar.com. My registrar offers DNS hosting for free, as part of my having bought my domain through them. If they didn’t, I could use a free service like ZoneEdit, or similar.

Step 2: My new hosting company tells me to set the nameservers to dns1.goodrack.com and dns2.goodrack.com. I look them right in the eye, tell them to “get bent”, and ask what the IP address of my new server will be. If they put up a fight, I tell them I can always find a better web host. That usually shuts them up.

Step 2 (alternate): I say “sure, whatever you say”, then do the following at a command line:

C:\otto\>nslookup
Default Server:  dns.mycompany.com
Address:  1.2.3.4

> server dns1.goodrack.com
Default Server:  dns1.goodrack.com
Address:  5.6.7.8

> set type=any
> mydomain.com
Server:  dns1.goodrack.com
Address:  5.6.7.8

mydomain.com      internet address = 111.222.111.222
(root)  nameserver = dns1.goodrack.com
(root)  nameserver = dns2.goodrack.com
dns1.goodrack.com    internet address = 5.6.7.8
dns1.goodrack.com    internet address = 5.6.7.9

Now I know my new server’s IP address from there (it’s 111.222.111.222).

Step 3: I go to myregistrar.com’s site, edit my DNS settings (specifically, I change the A record for mydomain.com to point to that new IP address), and then I wait for a couple hours or so, max (since my registrar lets me set my own TTL, I can do what I like with it. Two hours is a decent tradeoff of time vs. functionality). Within 2 hours, every site on the whole blamed internet sees my new host.

Why is this better? Well, note that my nameservers never actually changed. Nameservers are set in the root domain lookup systems. Changes there not only take a while to propagate, but those servers are overloaded so caching values for nameservers are usually quite high. Individual host lookups though, not so much.

How a DNS request works:

  1. I ask my nameserver for example.com.
  2. It doesn’t know, so it goes and ask the root nameservers “Hey, who is the nameserver for example.com?”
  3. One of the 13 root nameservers says “Yes, example.com is serviced by dns1.somebody.com and dns2.somebody.com and here’s their IP address’s. Now leave me alone, I’m busy.”
  4. So my name server now goes and asks dns1.somebody.com, “Hey, do you know the IP for example.com?”
  5. And then dns1.somebody.com says “Sure, it’s 1.2.3.4″.

Lot of work. But note that my nameserver talked to TWO nameservers here. The root, and the actual nameserver for example.com. The TTL on the root lookup is not something I can adjust, usually. Or if I can, then it’s very difficult to do for most people. The TTL on the second is not nearly as hard, and doesn’t require all the root nameservers to be updated.

If you own a domain, then you need to own your DNS. Use a nameserver that you have control over, and which you will almost never change. You can change the addresses, you can change the MX records (for email), you can add TEXT records for SPF, and other DNS tricks all you want. But keep the nameserver location itself unchanged for as long as possible. Because when you do change it, the internet takes a long, long time to adjust to that fact. And you are then “offline” for quite a while.

To think of it another way: He who controls the DNS, controls the domain, as least for a while. Well, you’re going to change hosts a lot more often than you change domain names, right? So don’t give them your DNS control. No webhost should ever have your nameserver pointed to them unless you bought the domain name from them in the first place.

Shortlink: