Crontab is a command, commonly found in Unix and Unix-like operating systems, used to set instructions to be executed periodically.
Problem analysis: The command is not found, there may be a high probability that crontab is not installed. Installed on the line
execution yum install -y vixie-cron
to see the boot is enabled
to perform -e crontab
* */1 * * * ntpdate ntp.api.bz; hwclock -w(per hour synchronous virtual machines and hardware time)
