Setting a custom name server on an OpenStack instance

In an OpenStack tenant that is not allowed to create a network with neutron net-create, the name server can be set via cloudinit. The resolv-conf module although documented in the examples is not always available. It can be worked around with

#cloud-config
bootcmd:
 - echo nameserver 4.4.4.4 | tee /etc/resolvconf/resolv.conf.d/head
 - resolvconf -u

for Ubuntu or

#cloud-config
bootcmd:
 - echo nameserver 4.4.4.4 | tee /etc/resolv.conf
 - sed -ie 's/PEERDNS="yes"/PEERDNS="no"/' /etc/sysconfig/network-scripts/ifcfg-eth0

for CentOS.