On Sun, 2 Sep 2012 14:30:08 -0600 Glenn English <g...@slsware.com> wrote:
> > My first real immersion in *nix and networking was with that > hardware and a pile of O'Reilly books on Internetting. So domain > names seemed vastly important to me. Apparently, it isn't to anybody > else: pretty much just a side effect of DNS, it looks like from > the responses I've gotten here. > I would have said so, and I believe I did. It's a matter of 'need to know'. Other people and computers in other networks need a FQDN to reach your public IP address(es), you and your network computers don't. Let me throw another item into the works as an example, one not present in all networks but present in most home and small business networks: NAT. My server and workstations all connect to web and other servers out on the Internet, and those servers all need to know my [single, fixed] public IP address. Do any of my computers need to know it? No, my DSL router knows it, and conveniently re-labels all my outgoing messages with it. None of my computers, not even the server, have any record of my public IP address, and there's nothing they could do with it if they did have it. They're all on private IP addresses. Similarly, none of my workstations need to know any domain name which can be used to reach the network. I lease about a dozen domains, none of which are returned by my PTR record. That resolves to a sub-domain of my ISP, which I never use for any networking purpose. My mail server knows about the sub-domain, and all my leased domains, as it must accept mail for all of them, but this is purely an SMTP function. All the domains have A records which resolve to my IP address, since all the domains have MX records which need them. Mail servers are naturally extremely fussy about domain names, but not much else is. As it happens, I run a full (BIND9) nameserver, purely internally, which of course exists for no other purpose than knowing host and domain names. To keep it happy, I've told it to use my main email domain name, but I could have picked any of them, or even something completely fictitious. I don't need a nameserver, or at least not a proper one, my router would do enough of a job for most purposes, but I feel I need to know at least the basics of running a real nameserver. So nominally, all my workstations (three or four) are 'in' my main email domain, but this has no actual meaning to them. To make full use of the nameserver, they all need to know the local search domain (in /etc/resolv.conf of the Linux machines), which will be appended to a bare hostname, but they don't use this domain name for anything but their own nameserver lookups. If I didn't run BIND (or an equivalent), all the computers would need to be in each others' /etc/hosts, a file that even Windows computers have, but only by hostname, not FQDN. In that case, I wouldn't need a domain name anywhere in the network other than in the SMTP server. I've tried to convey here the independence between a small NAT-connected network and the URL(s) used to reach it from the Internet. A local domain name is much more important for networks which have multiple public IP addresses and a dedicated (actually at least two) public DNS server, but these days it's only fairly sizeable businesses which have to operate that way. Most small and medium businesses are fine on a single public IP address, with a few DNS records at their domain host. And even in what appears to be a fully public network, the chances are that the real physical machines are on private IP addresses behind one-to-one NAT and have completely different hostnames from their public URLs... -- Joe -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20120902233727.7d91d...@jretrading.com