UCP requires that the system clocks on all the machines in a UCP cluster be in sync or else it can start having issues checking the status of the different nodes in the cluster. To ensure that the clocks in a cluster are synced, you can use NTP to set each machine's clock.
First, on each machine in the cluster, install NTP. For example, to install NTP on an Ubuntu distribution, run:
sudo apt-get update && apt-get install ntp
On CentOS and RHEL, run:
sudo yum install ntp
On SUSE Linux, run:
sudo zypper ref && zypper install ntp
This will install NTP on each machine and start ntpd, which is a daemon which periodically syncs your machine's clock with a central server. To sync the clocks right away, on each machine run:
sudo ntpdate pool.ntp.org
You can check to see if your machine's time is in sync with its NTP servers by running:
sudo ntpq -p
The output will look similar to the following:
remote refid st t when poll reach delay offset jitter ============================================================================== 18.104.22.168 22.214.171.124 2 u 24 64 1 60.391 4623378 0.004 time-a.timefreq .ACTS. 1 u 23 64 1 51.849 4623377 0.004 helium.constant 126.96.36.199 2 u 22 64 1 71.946 4623379 0.004 tock.usshc.com .GPS. 1 u 21 64 1 59.576 4623379 0.004 golem.canonical 188.8.131.52 2 u 20 64 1 145.356 4623378 0.004
The offset column shows how many milliseconds your machine's clock is out of sync with its NTP servers. Warnings are issued in the UCP UI if a time offset of more than 500 miliseconds is detected between members of the UCP cluster.