パッケージ更新

uname -a
yum check-update
yum update

chronyの設定

yum list chrony
ls -l /etc/chrony.conf*
cp -pi /etc/chrony.conf /etc/chrony.conf.000
ls -l /etc/chrony.conf*
diff -u /etc/chrony.conf{,.000}

systemctl status chronyd.service
ps -ef | grep chronyd | grep -v grep
chronyc sources
chronyc tracking
chronyc sourcestats
chronyc -a makestep

systemctl restart chronyd.service

サービスの自動起動設定と解除

systemctl list-unit-files  -t service
systemctl is-enabled chronyd.service

systemctl disable chronyd.service
systemctl enable chronyd.service

パッケージ削除と確認

yum remove chrony
yum list chrony

パッケージ導入

yum install ntp
yum list ntp

サービス起動

systemctl status ntpd.service
systemctl start ntpd.service