The linuxcrontab command regularly restarts apache and mysql

The apache and mysql services are automatically restarted on a regular basis without restarting the server. The procedure is as follows: 1. Restart apache and mysql services on a regular basis at and every day without restarting the server. The procedure is as follows:
I. Restart apache and mysql services at and every day
[Root @ www bin] # Cd/Opt/
[Root @ www opt] # vim reboot.txt
Enter the following content in the reboot.txt.txt file and save it.
0 12 *** service HttpdRestart
0 12 *** service mysqld restart
0 16 *** service httpd restart
0 16 *** service mysqld restart
2. Add the new file to the cron service.
[Root @ www opt] # CrontabReboot.txt
[Root @ www opt] # crontab-l
0 12 *** service httpd restart
0 12 *** service mysqld restart
0 16 *** service httpd restart
0 16 *** service mysqld restart
Iii. Restart the cron Service
[Root @ www opt] #/sbin/service crond restart
Note:
Cron is a linux scheduled execution tool that can run jobs without human intervention. Since Cron is a built-in service in Linux, but it does not automatically get up, you can use the following methods to start and close this service:
/Sbin/service crond start // start the service
/Sbin/service crond stop // close the service
/Sbin/service crond restart // restart the service
/Sbin/service crond reload // reload the configuration
Basic time table format:
* *** Program
Minutes, days, months, and weeks Command
The 1st column indicates minute 1 ~ 59. Each minute is represented by * or */1.
The first column indicates the hour 1 ~ 23 (0 indicates 0 points)
The 3rd column indicates the date 1 ~ 31
The 4th column indicates the month 1 ~ 12
The Identification Number of column 5th is from day of the week to day ~ 6 (0 indicates Sunday)
6th columns of commands to run
When Column 1st is set to *, the program is executed every minute. When Column 2nd is set to *, the program is executed every hour, and so on.
When Column 1st is a-B, it indicates that execution is performed from the minute a to the minute B. If Column 2nd is a-B, it indicates that execution is performed from the hour a to the hour B, other analogy
When Column 1st is */n, it indicates execution is performed every n minutes. If Column 2nd is */n, it indicates execution is performed every n hours.
When Column 1st is a, B, c ,... a, B, c ,... execute in minutes. The 2nd columns are a, B, c ,... a, B, c... execute in hours, and so on
Some examples of crontab files:
30 21 ***/usr/local/etc/rc. d/lighttpd restart
The above example indicates restarting lighttpd at every night.
45 4, 10, 22 **/usr/local/etc/rc. d/lighttpd restart
The preceding example indicates that the lighttpd is restarted at on the 1st, 10th, and 22th of each month.
10 1 ** 6, 0/usr/local/etc/rc. d/lighttpd restart
The preceding example indicates restarting lighttpd at every Saturday and Sunday.
0, 30 18-23 ***/usr/local/etc/rc. d/lighttpd restart
The preceding example indicates restarting lighttpd every 30 minutes between and every day.
0 23 ** 6/usr/local/etc/rc. d/lighttpd restart
The preceding example indicates restarting lighttpd at every Saturday.
**/1 ***/usr/local/etc/rc. d/lighttpd restart
Restart lighttpd every hour
* 23-7/1 ***/usr/local/etc/rc. d/lighttpd restart
Restart lighttpd every hour between PM and PM.
0 11 4 * mon-w Ed/Usr/local/etc/rc. d/lighttpd restart
Restart lighttpd from every Monday to Wednesday on the 4th of each month.
0 4 1 jan */usr/local/etc/rc. d/lighttpd restart
Restart lighttpd at on January 1, January 1.