Server reverts to DHCP from time to time

Question

I have an Ubuntu 10.04 server with static IP address configuration:

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
address 192.168.2.51
network 192.168.2.0
netmask 255.255.255.0
broadcast 192.168.2.255
gateway 192.168.2.1

From time to time (between once a month or once every 3 days depending on load) the server will spontaneously discard this IP address and change to one configured via DHCP.

When this happens I need to SSH into the server (using its .local hostname) and do /etc/init.d/networking restart to get it to use the static IP again.

How can this happen, and more importantly, how can I stop it?

Answer 1

Is it possible that there is a DHCP client process still running?

Perhaps you changed the server from DHCP to static, performed a network restart but the dhclient process didn't exit correctly.

You can do

johnf@zoot:~$ ps ax | grep [d]hclient
28248 ?        S      0:00 /sbin/dhclient # Other args

to check.

If so kill this process off or reboot.

Answer 2

Why not configure the DHCP server to hand out the IP address you want based on the server's MAC address? With ISC dhcpd (the de-facto standard DHCP server for unix systems) just put something like this in the config (make sure that subnet mask and gateway are already configured properly):

host server01
{
    hardware ethernet MA:CA:DD:RE:SS;
    fixed-address 192.168.2.51;
    option host-name "server01";
}