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Old 03-13-2008, 08:29 AM   #1
Registered: Apr 2005
Location: Durban
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Hostnames, Domains, Realms, Samba Groups, etc

Can anyone give me a clearer idea of the significance of the various 'names' that a server might have.

For example, when apache starts up it says "could not determine the server's fully qualified domain name using localhost instead"

Why do I need the FQDN? Does it need to be a FQDN with a qualified TLD, such as .com or Can I use a made up name like comp.frieddomain.lan?

Samba appears to need a GROUP. Should this be FRIEDDOMAIN? I see Samba also uses realms. Should this be the same as the FQDN?

Kerebos also deals in REALMS. Are these the same as the one Samba is using? or Apache? Does it matter?

Squid needs a unique_hostname. What is it asking for. The Domain? The Realm? The FQDN?

Old 03-13-2008, 09:01 PM   #2
Registered: Nov 2006
Location: Seattle, WA
Distribution: Fedora
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1. A FQDN is of the form It has at least 2 parts, separated by a dot. Whether this must be "legal" depends on whether the machine with this name is going to be visible on the public Internet, where a scheme called the Domain Name System (DNS) operates. If your machine needs to be accessible over the Internet, the way other machines will get there is by translating the FQDN into an IP address, using the DNS to do that translation. In that case, you need to be legal.

If, on the other hand, your server is attached to an isolated network which does not participate in the public DNS, you are free to come up with any FQDN you like. Beware, though, because if your isolated net eventually becomes attached to the public Internet, you will have to go back and change the FQDN for your server, and change any references to that name wherever they are (user's browser bookmarks, for example).

2. As with many things in this networked world, Samba is bound by the work of the Microsoft Empire. It needs a workgroup to identify related machines that ought to be allowed free (or freer) access to each other's files, printers, and other services. This workgroup does not need to be related in any way the FQDN. It must, however, be the same for all the members who want to share info. Samba knows about a realm only if it is involved in an Active Directory scheme for authenticating users. In that case, it uses the Kerberos realm as part of the user identification. More info is available on the implications of all this at

3. Squid wants either the FQDN or the first part of it. Look at the documentation to decide which is wanted in a particular place.


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