[PROBLEM]
During boot when bringing up the local loopback interface or other network devices, the error message "RTNETLINK: File exists" appears - causing the bootscripts to assume a failure.
[INFO]
As far as I´ve found out, this error simply indicates that something tries to bring up the same interface more than once.
[SOLUTION]
1) for the loopback:
Edit "/etc/rc.d/init.d/localnet" and swap the 2 lines responsible for bringing the "lo"-interface up (using the "ip" command)
2) for other network devices:
In our case we´ve had 2 entries in the "/etc/sysconfig/network-devices/ifconfig.eth0" directory. One configured to use DHCP-client, and one using a static IP.
The bootscript (/etc/rc.d/init.d/network) tried to execute both which lead to "RTNETLINK: File exists", because the interface was already up.