Let’s say that you have a cluster of 6 nodes and you do not have a DNS server.
How do you map the IPs to their perspective hostnames properly so that every node in the cluster can detect the other node’s hostname? We need to bypass the automatic lookup.
I have 6 nodes with the following IPs and hostnames.
128.197.115.158 buhpc1 128.197.115.7 buhpc2 128.197.115.176 buhpc3 128.197.115.17 buhpc4 128.197.115.9 buhpc5 128.197.115.15 buhpc6
Now, we edit every node’s /etc/hosts file.
For all nodes
vi /etc/hosts
The original files look like this:
1 2 | 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 |
We change the files to look like this:
1 2 3 4 5 6 7 8 | 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 128.197.115.158 buhpc1 128.197.115.7 buhpc2 128.197.115.176 buhpc3 128.197.115.17 buhpc4 128.197.115.9 buhpc5 128.197.115.15 buhpc6 |
systemctl restart network
Make sure that the /etc/hosts file is exactly the same on all 6 nodes! Then, after restarting all the networks with the above command, the /etc/hosts file with bypass the automatic DNS lookup and relate those hostnames to those IP addresses!
Testing
If I am on buhpc1, and I do:
ping buhpc2
I will be pinging 128.197.115.7. In the /etc/hosts file, we have defined 128.197.115.7 as buhpc2.