The following procedure was tested on Bright 8.2 on CentOS 7.
WARNING: Please note that an update of certain Bright packages can remove some of the changes that were done manually here. If the packages node-installer or node-installer-nfsroot are updated/reinstalled on the head node, then step 7 of this article has to be done again.
1 - Disable ntpd on the head node
Run the following commands on the head node:
# systemctl disable ntpd
# systemctl stop ntpd
# cmsh
% device use master
% services
% use ntpd
% stop
% set autostart no
% set monitored no
% commit
2 - Disable ntpd on the software images
Run the following commands on the head node (this has to be done for every software image)
# chroot /cm/images/<software images>
# systemctl disable ntpd
# exit
3 - Install chrony on the head node and software images
Run the following commands on the head node:
# yum install chrony
# yum install chrony --installroot=/cm/images/<software image>
… repeat this last step for every software image
4 - Configure chrony on the head node
On the head node, edit the /etc/chrony.conf file, and add the following line to it (replace the network with the network from which the compute nodes will access the head node)
allow 10.141.0.0/16
5 - Configure chrony on the software images
In every software image, edit the /etc/chrony.conf file. Within the file, comment all the lines starting with “server” and add a line which points to the IP address that the compute nodes use to reach the head node. For example:
server 10.141.255.254 iburst
6 - Configure the head node and compute nodes to manage chronyd
Run the following commands on the head node:
# cmsh
% device use master
% services
% add chronyd
% set monitored yes
% set autostart yes
% commit
% start
% category use <category of the nodes>
% services
% add chronyd
% set monitored yes
% set autostart yes
% commit
7 - Configure node-installer to use chrony instead of ntpd
Run the following commands on the head node:
# yumdownloader chrony libseccomp
# rpm -ivh chrony-3.2-2.el7.x86_64.rpm libseccomp-2.3.1-3.el7.x86_64.rpm --root=/cm/node-installer
Then configure the node-installer so the initial time synchronization will be done using chronyd. For this, edit the /cm/node-installer/linuxrc file in the head node and replace the line “timeout 10s ntpd -c /tmp/ntp.conf -q -g” with literally the following line (it automatically uses the IP address that the compute nodes use to reach the head node):
timeout 10 chronyd -q "server $NET_MASTER iburst"
8 - Reboot nodes to apply the changes
All the compute nodes have to be rebooted so the changes in the software images will be applied.