Showing posts from June, 2012

Secondary DNS Server in CentOS 6

Please consult this article to check how the primary DNS Server is configured in chroot environment.

A secondary DNS Server is used as a backup DNS Server in case the primary fails. The configuration is almost identical.

Here are the details:
Domain: testdom.inv
Primary: ns1.testdom.inv (
Secondary: ns2.testdom.inv (
Secondary DNS Server Phase1: Again, the host names must be properly specified. We have to modify the following lines in the mentioned files -

[root@centu ~]# vim /etc/sysconfig/network HOSTNAME=ns2.testdom.inv
[root@ns2 ~]# vim /etc/hosts ns2.testdom.inv ns2

Finally, we set the resolver IP to the primary DNS Server

[root@ns2 ~]# vim /etc/resolv.conf nameserver nameserver  Phase 2: Now we set up necessary packages -

[root@ns2 ~]# yum install bind bind-chroot Loaded plugins: fastestmirror, presto Determining fastest mirrors Setting up Install Process Resolving Dependencies --> Running transacti…

Primary DNS Configuration in CentOS 6 (with chroot)

This tutorial is based on a previous article. The configuration of the DNS Servers using chroot and not using chroot are almost identical. Here's how it's done -
Objective We would be configuring the primary DNS Server for the domain testdom.inv (yes, the top level domain is inv i.e. 'invalid').  The FQDN (Fully Qualified Domain Name) of the server is ns1.testdom.inv. This is a simulation, so you better get your Server off the Internet-
make sure the Server does not have any real IPmake sure that the file /etc/resolv.conf does not contain any IP address of a valid DNS Server.
Here is the IP Database
DNS Server Server Server
Procedure Phase1: The first thing when it comes to configuring any Server is setting up the hostname of the Server properly. We have to modify the following lines in the mentioned files -

[root@centu ~]# vim /etc/sysconfig/network HOSTNAME=ns1.testdom.inv…

Nagios Ping Problem

I'm using Nagios3 in my Debian 6 box for monitoring my network. My system pings periodically to check whether the Internet connection is okay or not.

The weird thing happened is that, when Nagios checks whether is reachable or not, it says "Network not found". However, I can ping manually.

root@dragonfly:~# /usr/lib/nagios/plugins/check_ping -H -c 100,90% -w 100,90% CRITICAL - Network Unreachable (

root@dragonfly:~# ping PING ( 56(84) bytes of data. 64 bytes from ( icmp_req=1 ttl=53 time=210 ms 64 bytes from ( icmp_req=2 ttl=53 time=229 ms ^C --- ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 1000ms rtt min/avg/max/mdev = 210.611/219.867/229.124/9.268 ms
After a bit of googling, here's what I found.

8-Jun was IPv6 da…