Lab 25: Configure Time Services

Objective Focus

Deploy, configure, and maintain systems: Configure time service clients

What is meant by time services?

In order understand to time services, we have to explain what NTP, or Network Time Protocol, is first. NTP is a networking protocol that that is used over the wire to synchronize the system clocks of computers with a remote source. NTP uses UDP port 123.

Even now, your computer is communicating with a time source to get an accurate clock. A time source can be on local network, over the internet, and radio clock. We mostly see devices connected to time sources over the internet. I recommend looking up atomic clocks, stratum levels and checking out https://ntp.org.

How does NTP work in RHEL?

In RHEL, NTP is handled by Chrony under Chronyd.service.

$ systemctl status chronyd.service

Run the above command to check that chronyd is running.
What time source is being used?

What file is used to manage the chrony service?

$ /etc/chrony.conf

$ man chrony.conf

In the chrony.conf file, important directives, or keywords, are the pool and server. The pool keyword points to a group or “pool” of servers. Chronyd binds itself to one of the servers and if one fails it will switch over automatically. The server directive lets you use a hostname or IP address of a single server.

Working with Chronyd

$ man chronyc

chronyc is a tool to help manage chronyd

First lets check the status

$ systemctl status chronyd.service

Make sure it is started, not already

$ systemctl start chronyd.service

Make sure it pertists after a reboot

$ systemctl enable chronyd.service

Making a change

Lets edit chrony.conf

$ vim /etc/chrony.conf

add time.google.com and comment out pool line

server time.google.com iburst

Restart the service

$ systemctl restart chronyd.service

More on Chronyc

Using chronyc, we’ll check if the new source is picked up

$ chronyc sources

Additionally, we can see clock stats

$ chronyc tracking

Addtional commands for managing time

$ man date

print or set the system date and time

$ date --set "2004-02-29 16:00:00"

Example in the man page setting the time to February 29, 2004 at 4 PM
This change does not persist.
Great for scripting.

$ man timedatectl

timedatectl - Control the system time and date
Running the command without options will output a summary of the time settings.

$ timedatectl list-timezones

$ timedatectl set-timezone America/New_York

Reboot and see if it persists!

Thats all for Time related services! And Check your that your firewall configuration is allowing port 123!!