Install Chrony as a lightweight time client for CentOS 6 virtual machines
Xen 4.x with a pv_ops kernel has no dependent wallclock, thus the virtual machine must maintain it's own clock. Using a full reference ntp server add significant weight to the VM and the platform. Chrony keeps good enough time with a reduced memory and CPU footprint.
Chrony is part of the EPEL repository for CentOS 5/6. Given the package has no other dependencies from EPEL it can be installed without enabling the EPEL repository (and just providing a path to the rpm).
# yum install chrony
OR
# yum install http://mirror.lucidsolutions.co.nz/epel/6/x86_64/chrony-1.25-2.el6.x86_64.rpm
Add the local ntp servers to the configuration. These are the physical hosts that run ntp to the outside world.
server 1.ntp.lucidsolutions.co.nz iburst server 2.ntp.lucidsolutions.co.nz iburst server 3.ntp.lucidsolutions.co.nz iburst server 4.ntp.lucidsolutions.co.nz iburst server 5.ntp.lucidsolutions.co.nz iburst
Start the service
# chkconfig chronyd on # service chronyd start
Links
Appendices
startup log
chronyd[5743]: chronyd version 1.25 starting
chronyd[5743]: set_config_hz=0 hz=100 shift_hz=7 basic_freq_scale=1.28000000 nominal_tick=10000
slew_delta_tick=833 max_tick_bias=1000
chronyd[5743]: Linux kernel major=2 minor=6 patch=32
chronyd[5743]: Selected source 2001:4428:225:9::2
chronyd[5743]: System clock wrong by -61.636815 seconds, adjustment started
