时间定时同步
1.查看时区:timedatectl
2.将硬件时钟调整为与本地时钟一致, 0 为设置为 UTC 时间：timedatectl set-local-rtc 1
timedatectl set-timezone Asia/Shanghai 设置系统时区为上海
3.timedatectl set-ntp no
4.timedatectl set-time '2021-01-11 10:00:00'
5.clock -w
timedatectl set-local-rtc 1
cd /etc/sysconfig/network-scripts
vi ifcfg-eth0
DNS2=172.20.7.9
echo "DNS2=172.20.7.9" >>/etc/sysconfig/network-scripts/ifcfg-eth0
cat /etc/sysconfig/network-scripts/ifcfg-eth0
systemctl restart network
ping ntp.zjhu.edu.cn
yum -y install crontabs
systemctl start crond.service
systemctl enable crond.service
systemctl status crond.service
crontab -e
0 */2 * * * ntpdate ntp.zjhu.edu.cn
*/1 * * * * /sbin/ntpdate ntp.zjhu.edu.cn
/sbin/ntpdate ntp.zjhu.edu.cn
yum install -y ntpdate
systemctl start ntpdate.service
systemctl status ntpdate.service
systemctl enable ntpdate.service
find / -name CentOS-7.6-x86_64-DVD-1810.iso
mount -o loop /u01/CentOS-7.6-x86_64-DVD-1810.iso /mnt
mount -o loop /u01/bak/CentOS-7.6-x86_64-DVD-1810.iso /mnt
mv /etc/yum.repos.d/*.repo /etc/yum.repos.d/bak/
echo "[base]" >> /etc/yum.repos.d/123.repo
echo "name=123" >> /etc/yum.repos.d/123.repo
echo "baseurl=file:///mnt" >> /etc/yum.repos.d/123.repo
echo "gpgcheck=0" >> /etc/yum.repos.d/123.repo
echo "enable=1" >> /etc/yum.repos.d/123.repo
yum makecache