When installing a minimal CentOS 6 system, minimal really, really means minimal. After a reboot the network interfaces do not start, so network connectivity is non existing.
Looking into that I noticed that the file
/etc/sysconfig/network-scripts/ifcfg-eth0 contained
DEVICE=eth0 HWADDR=11:22:33:44:55:66 NM_CONTROLLED=yes ONBOOT=no BOOTPROTO=dhcp TYPE=Ethernet USERCTL=no PEERDNS=yes IPV6INIT=no
The lines that mess things up are NM_CONTROLLED=yes meaning the
interfaces are managed with NetworkManager, which isn’t actually
installed as part of a minimal install. You want a minimal install, you
get a minimal install. And ONBOOT=no, meaning do not start the interface on boot.
How stupid is that!
The trick is to run something like system-config-network-tui to set
the IP addresses manually, but as you might imagine, that’s not
installed either.
So you best edit /etc/sysconfig/network-scripts/ifcfg-eth0 by hand and
set it to: ~ DEVICE=eth0 HWADDR=11:22:33:44:55:66 NM_CONTROLLED=no
ONBOOT=yes BOOTPROTO=none TYPE=Ethernet USERCTL=no PEERDNS=yes
IPV6INIT=no IPADDR=192.168.0.1 NETMASK=255.255.255.0
GATEWAY=192.168.0.254 DNS1=192.168.0.254 ~
The USERCTL=… line is optional: If set to yes it lets non-root
users control the interface.
After setting this a service network restart will do the trick.