1. Scheduled task scheduling crontab
1. Introduction to scheduled task scheduling crond
①Task scheduling: The system executes specific commands and programs at a certain time
②Task scheduling classification: system work (virus scanning), user work (backup mysql database)
2. Scheduled task scheduling crond schematic diagram
3. Syntax of task scheduling
crontab[ options]
4. Common options
-e edit scheduled tasks
-l displays scheduled tasks
-r deletes all tasks for the current user
5.Quick Start Case
Mission requirements
Query the detailed directory under /etc every 1 minute and append the results to /tmp/to.txt
Steps to achieve
①Edit scheduled tasks crontab -e
There is a space between * , wq save and exit
6. The placeholder indicates the time, day, month, and week.
7.Explanation of special symbols
8.Case _
2. Case
1. Every 1 minute, append the current date information to the /tmp/mydate.txt file
①Write the script file vim /home/mytask1.sh
date >> /tmp/mydate.txt
②Give the script file executable permissions
rwx=7
r=4
chmod 744 /home/mytask1.sh
③Edit scheduled tasks crontab -e
*/1 * * * * /home/mytask1.sh
2. Every 1 minute, append the current date and calendar information to the /tmp/mydate.txt file
①Write the script file vim /home/mytask2.sh
date >> /tmp/mycal.txt
cal >> /tmp/mycal.txt
②Give the script file executable permissions
rwx=7
r=4
chmod 744 /home/mytask2.sh
③Edit scheduled tasks crontab -e
*/1 * * * * /home/mytask2.sh
3. Back up the mysql database testdb to the file mydb.bak at 2:00 a.m. every day.
①Write the script file vim /home/mytask3.sh
/usr/local/mysql/bin/mysqldump -u root -p root testdb > /tmp/mydb.bak
②Give the script file executable permissions
rwx=7
r=4
chmod 744 /home/mytask3.sh
③Edit scheduled tasks crontab -e
0 2 * * * /home/mytask3.sh
crond related instructions:
1) conrtab -r: Terminate task scheduling.
2) crontab –l: List the currently scheduled tasks
3) service crond restart [restart task scheduling]