Overview
This guide will help in installing and configuring chrony
service.
Applies To
·
RHEL 7, CentOS 7
Pre-Requisites
·
None
Advantages – Chrony
Before we implement chrony in the environment there few considerations and advantages that chrony provides over NTP and they are listed in below table;
|
Chrony
|
NTP
|
|
Servers that are not permanently connected to the network
|
Servers that are permanently connected
to the network
|
|
Servers that are not permanently powered on
|
Servers that are permanently powered
on
|
|
Applications / servers that need date
and time synchronization faster
|
Applications / servers that can wait
longer time for synchronization of date and time
|
|
Auto correct smaller drifts and
offsets
|
Auto correction of smaller drifts and
offsets is not very critical
|
|
Temperature changes that are significantly
higher, which affect the stability of hardware clock
|
Temperature changes that are ideal and
cool temperature and stability of hardware clock is always apt
|
|
Where system restarts take longer
duration to boot up depending on the environment and application dependencies
|
Where system restarts doesn’t longer
duration to boot up the environment and application dependencies are more or
less doesn’t exists.
|
|
It can work well even if the external
time references are only intermittently accessible
|
NTP needs regular pooling of time
reference to work well
|
|
Apt for systems are virtual machines,
wherein machines that are unstable or broken
|
Ideal for systems are physical machines,
wherein machines that are stable
|
|
Works well even if there is network
congestion
|
NTP Needs regular pooling
|
|
Synchronizes the clock faster
|
Can’t synchronize the clock faster
because it needs regular pooling of time
|
|
Adapts quickly to sudden change in rate
of clock, temperature changes
|
Takes longer time to adapt to
temperature changes
|
Disadvantages – Chrony
Even though there are advantages in implementing chrony in the that are few drawbacks as well that are listed in the below table;
|
Chrony
|
NTP
|
|
chronyd uses NTP version
3 (RFC 1305), which is compatible with version 4
|
ntpd fully
supports NTP version 4 (RFC 5905), including broadcast, multicast, many cast
clients and servers, and the orphan mode. ntpd also supports extra authentication
schemes based on public-key cryptography (RFC 5906).
|
|
chronyd relies
on other programs, for example gpsd, to access the data from the
reference clocks
|
ntpd includes
drivers for many reference clocks
|
Note: Chrony can be implemented ideally on mobile of virtual systems.
Install Package
Before the chrony package is installed To install the chrony
package, run the command;
yum list installed | grep chrony
yum install -y chrony
Enable Chrony Daemon
After installation, we have to enable the chrony service to start at OS boot, run the command;
systemctl enable chronyd
Start Chrony Daemon
To start of the chrony service, run the command;
systemctl start chronyd
Status Chrony Daemon
To verify the status of the chrony service, run the command;
systemctl status chronyd -l
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