Infrastructure network services (DNS, NTP...)

DNS

The default gateway usually (depending on the network) works as a DNS server. In any case, the DNS servers to be used are pushed by the DHCP when the VM starts, so the DHCP client of the image must be configured (if this is not already the case) to use this dynamic configuration.

NTP

On the cloud, a good practice is to synchronize time onto the underlying physical host. The simplest way to achieve this configuration is to use chronyd and set it up so as to use the host clock :

# uninstall ntpd if installed
$ yum remove -y ntpd

# install chronyd
$ yum install -y chronyd

# host clock sync setup
echo ptp_kvm > /etc/modules-load.d/ptp_kvm.conf
sed -i -e '/refclock/d' -e '/^server/d' /etc/chronyd.conf
cat >> /etc/chronyd.conf <<EOF
refclock PHC /dev/ptp0 poll 2
EOF