time_services

How does linux gets it's time?

• While booting, the system gets its time from the hardware clock
• System time is set next, according to the hardware clock
• Internet time can be used to synchronize time

commands involved in managing time

• hwclock is used to set hardware time
• Also use it to synchronize time
  • hwclock --systohc
  • hwclock --hctosys
• date is used to show and set time
• timedatectl is used to manage time and time zone configuration

Commands involved in managing linux time

NTP

Info

• NTP (Network Time Protocol) is a protocol used to synchronize the clocks of computers and other devices over a network
• chronyd is the default RHEL 9 NTP service

3 parameters

Remember

Use /etc/chrony.conf to specify synchronization parameters

• pool 2.rhel.pool.ntp.org iburst configures a pool of NTP servers
• server myserver.example.com configures a single NTP time source

Use iburst to permit fast synchronization

After modifying its contents, use systemctl restart chronyd to restart the chronyd service

Use chronyc sources to verify proper synchronization

• make sure NTP service is active

yum install chrony
vim /etc/chrony.conf

difference_between_server_and_pool

systemctl restart chronyd
chronyc sources
timedatectl
timedatectl set-ntp true