/etc/sysconfig/network is what assigns the hostname to your particular
server. This is also where CentOS writes the hostname when you initially
install the OS.
/etc/hosts provides a mechanism for mapping that hostname to an IP
address. This is one of several ways to map ip's to hostnames.
I use /etc/sysconfig/network to "name" my machines and then enter that
value into /etc/hosts. i.e.
/etc/sysconfig/network
HOSTNAME="vpn-gateway"
/etc/hosts
127.0.0.1 localhost localhost.localdomain
10.0.0.1 vpn-gateway vpn-gateway.mydomain.com
the second entry is an "alias" to vpn-gateway. If you were to ping
either one you would get a response from 10.0.0.1.
There is an order of operations that CentOS uses to resolve host names.
By default the first attempt is in the hosts file. If it doesn't find
anything there is will try DNS, if nothing is there it will try WINS,
and so on. If you have a DNS server in your network you could add a
record to resolve vpn-gateway.mydomain.com to 10.0.0.1 and not fill in a
/etc/hosts value at all. (Providing /etc/resolv.conf is setup to look
at that DNS server)
Someone correct me if I am wrong, but this is what I understand to be
correct.
-----Original Message-----
From: centos-bounces@xxxxxxxxxx [mailto:centos-bounces@xxxxxxxxxx] On
Behalf Of Scott Silva
Sent: Wednesday, November 29, 2006 2:02 PM
To: centos@xxxxxxxxxx
Subject: [CentOS] Re: hostname setting
MrKiwi spake the following on 11/29/2006 1:34 PM:
> Can someone with far more knowledge than me help here?
>
> I have a co-worker with a question;
> "
> Where should i set the server's hostname?
> There seems to be multiple places and i don't understand the
differences.
> 1. # hostname mailserver.mydomain.com
> 2. # echo "127.0.0.1 mailserver mailserver.mydomain.com">>/etc/hosts
> 3. # vi /etc/sysconfig/network, add "HOSTNAME=mailserver.mydomain.com"
>
> So far i think i understand that postfix likes to see the hostname in
> the hosts file, but things i have read imply that postfix is pretty
> clever at working it out from multiple places.
> Apache also seems to be clever, but the conf file recommends that you
> hard code the server name into the config. If you don't, where does
> apache look?
> If you set the hostname during an install, where is that written?
> If i use method 1 above ("hostname mailserver.mydomain.com") i seem to
> have to do that at every boot (or script it of course) whereas the
edit
> to /etc/hosts or /etc/sysconfig/network would survive restarts.
>
> I have read the information in "man hostname" and understand that
> "hostname -f" gets its info from the hosts file, but where does the
> function "gethostname" get its info from?
>
> Finally - which method do you all use to set you hostname?
> "
>
> Thanks all,
>
> MrKiwi
I have my hostname in both /etc/sysconfig/network and /etc/hosts.
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