IntroductionThe first basic requirement for your systems when deploying ICO 2.4 is to have DNS name resolution working correctly. For some reason or another, this is the area that has the largest number and most frequent problems in every single enterprise. So this short post is meant to help you get something going quickly, normally in a test environment, until you can communicate with your networking team to get the problems solved permanently.
My Simple EnvironmentMy test environment is the demo configuration with one RHEL 6.6 server with 8 cores and 32GB of RAM, with KVM for virtualization.
Setting Your HostnameYou need to set your hostname to a Fully Qualified Domain Name (FQDN), and in a test environment, the format just needs to be correct - the actual name doesn't have to be registered anywhere. For example, I named my host ico24demo.mynet.foo. I don't care if .foo is a valid root or not because I get to make the rules in my own environment.
To permanently set your hostname to an FQDN if you didn't do it at install time, you need to edit the file:
If you don't want to reboot to have it set, also run the following as root:
Update Your Hosts FileYou also need to update your /etc/hosts file with your hostname and IP. So edit /etc/hosts and add that information for your host. In my environment, my hostname is ico24demo.mynet.foo and my static IP address is 192.168.1.250. So here's my /etc/hosts entry:
192.168.1.250 ico24demo.mynet.foo ico24demo
dnsmasq is a simple DNS server (and DHCP and some other things) that we'll configure locally for name resolution.
rpm -q -a | grep dnsmasq
If it's not installed, install it.
Assuming it is installed, make sure it's not already running with:
ps -ef | grep dnsmasq
If it is, kill it with:
service stop dnsmasq
The above may or may not work. If the process is still running kill it with the kill command.
And now that your /etc/hosts file has your host information, start dnsmasq with:
service start dnsmasq
Test Your New DNS ServerProbably the easiest way to test your server is to first edit your /etc/resolv.conf file to set your nameserver to your local machine. So my local IP is 192.168.1.250, and the IP address of my subnet's nameserver is 192.168.1.1. So in my /etc/resolv.conf file, I have the following:
# Generated by NetworkManager
The correct output for me is:
250.1.168.192.in-addr.arpa domain name pointer ico24demo.mynet.foo.
If you get something different, go back over the steps above. But if it's correct, keep going.
Make the Nameserver Change PermanentGo to System->Preferences->Network Connections to set your nameserver to be your local IP address.
A non-GUI way to do this is to update your /etc/sysconfig/network-scripts/ifcfg-eth0 file to set the DNS server.