CentOS eth0 not starting

Question

Why would my new CentOS Virtual Machine not start eth0 on startup? I have to start it manually every time. How can I fix this?

Thanks.

Answer 1

Make sure ONBOOT="yes" is in /etc/sysconfig/network-scripts/ifcfg-eth0. If you're using NetworkManager, make sure that service starts on boot (chkconfig NetworkManager on), otherwise, if you're using the old network service, make sure it starts on boot (chkconfig network on).

Answer 2

Regarding CentOS6 not enabling the network interface by default: it (in the GUI installer, at least) does its very best to prevent the interface from being set up properly, but this can be defeated via a checkbox that's hidden a couple dialogs deep from the main flow.

On the screen where you enter the hostname, the "Configure Network" button at the bottom takes you to a "Network Connections" dialog. Select eth0, then the "Edit" button takes you to an "Editing System eth0" dialog, which has a "Connect automatically" checkbox. If you leave this box unchecked, you get ONBOOT="no" in /etc/sysconfig/network-scripts/ifcfg-eth0; if you check it, you get ONBOOT="yes". I don't know if the checkbox affects any other configs, but I've yet to notice any different behavior. Why the box isn't checked by default, I can't begin to imagine.