I’ve had to do this many times, and have never really found a good, definitive tutorial on this until now. Because of this, I decided to just copy and paste it into my blog in case they take it down at some point.

The following came from: http://www.cpqlinux.com/hostname.html

Checking your Linux host name

First, see if your host name is set correclty using the following commands:

uname -n
hostname -a
hostname -s
hostname -d
hostname -f
hostname

If the above commands return correctly with no errors then all may be well;
however, you may want to read on to verify that all settings are correct.

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Configuring /etc/hosts

If your IP address is assigned to you by a DHCP server, then /etc/hosts is configured as follows:

127.0.0.1	mybox.mydomain.com	localhost.localdomain localhost mybox

If you have a static IP address, then /etc/hosts is configured as follows:

127.0.0.1	localhost.localdomain localhost
192.168.0.10	mybox.mydomain.com	mybox

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Setting the Host Name using “hostname”

After updating the /etc/hosts file correctly, the “hostname” command should be run as follows to set your hostname:

hostname mybox.mydomain.com

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Checking /etc/HOSTNAME (if present)

You may or may not have the file /etc/HOSTNAME:

mybox.mydomain.com

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Checking /etc/sysconfig/network

If you have a static IP address, then /etc/sysconfig/network is configured as follows:

NETWORKING=yes
HOSTNAME="mybox.mydomain.com"
...

If your IP address is assigned to you by a DHCP server, and you wish to update the local DNS server through Dynamic DNS, then /etc/sysconfig/network is configured as follows:

NETWORKING=yes
HOSTNAME="mybox.mydomain.com"
DHCP_HOSTNAME="mybox.mydomain.com"
...

It makes more sense to move this “DHCP_HOSTNAME” variable into /etc/sysconfig/network-scripts/ifcfg-eth0 (or appropriate NIC cfg file). So the above section has been moved, see below. If you have only 1 NIC, then the above struck section works fine, but with more than 1 NIC it makes no sense. Maybe this is true for the “‘HOSTNAME” line too, maybe that line should be moved into /etc/sysconfig/network-scripts/ifcfg-eth0 as well. I will investigate further. By default RHL places HOSTNAME=localhost.localdomain in /etc/sysconfig/network.

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Checking /proc/sys/kernel/hostname

This is checked with the following command:

cat /proc/sys/kernel/hostname

If you need to set this file, you can either reboot or set it now with the following command:

echo mybox.mydomain.com > /proc/sys/kernel/hostname

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Dynamic DNS – Updating the local DNS server with your host name and DHCP IP

For Red Hat Linux if you receive your IP address from a DHCP server, you may update the local DNS server by adding the following line to the correct ifcfg file in /etc/sysconfig/network-scripts, such as ifcfg-eth0 or ifcfg-eth1:

DHCP_HOSTNAME="mybox.mydomain.com"

or if running Debian, edit /etc/network/interfaces as follows (adding the hostname line):

iface eth0 inet dhcp
    hostname mybox.mydomain.com