I'm writing this note because of a very frustrating behaviour in OpenSUSE that resets or disconnects a manually set static IP number after a short period of time (after around a minute or so). I couldn't find anything related to this by Googling...
Edit the file /etc/sysconfig/network/ifcfg-<device>
BOOTPROTO='static' IPADDR='10.0.0.1/24' STARTMODE='nfsroot'
STARTMODE is the particular parameter to get right - yast2 normally substitutes 'auto' here, which is the cause of the problem.
Some information can be found in the file /etc/sysconfig/network/ifcfg.template.