Setup and Test Bind DNS Zone File Replication to Slave Servers on CentOS

Scenario: You are on-boarding/bringing up a new Bind DNS server (say NSHost3 – to replace/upgrade your existing Bind DNS server (NSHost2 – You have installed Bind 9.8 as shown on the new server [root@NSHost3 ~]#  named -vBIND 9.8.2rc1-RedHat-9.8.2-0.47.rc1.el6_8.1[root@NSHost3 ~]# You want to configure NSHost3 as slave server for some of the zones are primarily hosted on NSHost1 ( in your other Data centre You are NOT running or have allowed the tcp/udp port#53 in your iptables Firewall on both NSHost1 and NSHost3 servers   Implementation: Configuring your new server NSHost3 as slave to NSHost1 server requires updating named.conf […]


FIX: CentOS 6.8 Minimal Install: Device eth0 does not seem to be present, delaying initialization

Scenario: You are running your CentOS virtual machine on XenServer with a Static IPv4 IP-Address. All of sudden your CentOS system loses network connectivity. Upon checking you notice that none of the Network adapters are detected.  The IP-address assigned gets allocated to other systems on the network. Upon attempting to run command ‘service network restart’, you encounter error message: Bringing up interface eth0: Device eth0 does not seem to be present, delaying initialization. [FAILED] You notice that Same error persists even when you add more NICs to the system Same error persists even when you remove or manually update MAC […]

Setup or Migrate Postfix SMTP relay server on CentOS 6.5

Scenario: You have a External SMTP relay host configured on older and physical Linux box which you would like to migrate to CentOS host in a virtualized environment. The older Linux box running on Ubuntu 6.06 + Postfix 2.2.10.  You want to migrate it to a virtual machine running CentOS 6.5 + Postfix 2.6.6. OS and Postfix Version details of existing server: root@NSHost1:~# lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description:    Ubuntu 6.06.2 LTS Release:        6.06 Codename:       dapper root@NSHost1:~# root@NSHost1:~# postconf -d | grep mail_version mail_version = 2.2.10 root@NSHost1:~# OS and Postfix Version details of new server: […]