mv /etc/localtime /etc/localtime.bak
ln -s /usr/share/zoneinfo/Europe/Kiev /etc/localtime
Over time, clocks may drift ahead or fall behind, so they need to be periodically synchronized with reference time sources. In CentOS, this is done using the ntpd daemon.
Install the ntpd daemon if it is not already present in the system:
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# yum -y install ntp |
Synchronize the time once:
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# ntpdate pool.ntp.org |
If you receive a message like the NTP socket is in use, exiting, it means the ntpd daemon is already running. In this case, stop it:
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# systemctl stop ntpd |
Configure the CMOS clock in the BIOS to use UTC time:
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# hwclock --systohc --utc |
This command sets the hardware clock time to match the system time. As you may recall, we synchronized the system time using the commands above.
Check the contents of the /etc/sysconfig/clock file to ensure the system sets the local time correctly after boot. For Kyiv, it should contain the following:
ZONE="Europe/Kiev" UTC=true ARC=false
Configure the ntpd daemon to start automatically when the operating system boots:
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# systemctl enable ntpd |
Start the time synchronization daemon:
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# systemctl start ntpd |
Check the system time using the command:
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# date |
It should match the actual value.
Let's check whether the system time is synchronized with reference time servers (NTP servers) and if everything is in order using the ntpq -p command:
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# ntpq -p remote refid st t when poll reach delay offset jitter==============================================================================+ntp1.hetzner.de 192.53.103.103 2 u 98 1024 377 3.850 2.293 1.203*ntp2.hetzner.de 192.53.103.104 2 u 335 1024 377 0.641 3.480 1.202+ntp3.hetzner.de 192.53.103.104 2 u 322 1024 377 0.736 4.117 1.211 |
The ntpd daemon enables the "11 minute mode" in the Linux kernel. In this mode, system and hardware clocks are synchronized every 11 minutes. By default, this mode is disabled and is enabled only when a service requests it. The ntpd daemon is responsible for enabling this mode. Therefore, there is no need to additionally synchronize the hardware clock based on the system time.
P.S. Now the system and hardware clocks of your server will automatically synchronize with reference servers and always display the correct time.