In the actual production environment, there will always be some regular tasks, such as data backup, we can not always wait until that time to perform manually, then planning tasks will come into use.
One-time Planned Tasks
at
- One-time Planned Tasks
at [HH:MM] [YYYY-MM-DD]
Set up, press Ctrl + D to exit
1. Get the current time of the system
[root@localhost ~]# date 2019 Wednesday, 28 August, 2000:30:41 CST
2. Setting up one-time planning tasks
[root@localhost ~]# at 00:33 2019-08-28 at> rpm -qa | wc -l > /opt/test.txt at> <EOT> job 1 at Wed Aug 28 00:33:00 2019 [root@localhost ~]# atq 1 Wed Aug 28 00:33:00 2019 a root
3. Verification results
[root@localhost ~]# cat /opt/test.txt 1318
atq
- Query for planned tasks that have not yet been performed
[root@localhost ~]# atq 1 Wed Aug 28 00:33:00 2019 a root
atrm
- Delete planned tasks that have not yet been performed
[root@localhost ~]# at 00:35 2019-08-28 at> shutdown now at> <EOT> job 2 at Wed Aug 28 00:35:00 2019 [root@localhost ~]# atq 2 Wed Aug 28 00:35:00 2019 a root
[root@localhost ~]# atrm 2 [root@localhost ~]# atq
Periodic Planning Tasks
crontab
- Periodic Planning Tasks
- e: Editing the Scheduled Task List
- l: List shows scheduled tasks
- r: Delete the Scheduled Task List
- u: Designated user
- Configuration file:
[root@localhost ~]# cat /etc/crontab SHELL=/bin/bash PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root # For details see man 4 crontabs # Example of job definition: # .---------------- minute (0 - 59) # | .------------- hour (0 - 23) # | | .---------- day of month (1 - 31) # | | | .------- month (1 - 12) OR jan,feb,mar,apr ... # | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat # | | | | | # * * * * * user-name command to be executed
| parameter | Explain |
|---|---|
| branch | 0~59 integer |
| Time | 0~23 integer |
| day | 1~31 integer |
| month | 1~12 integer |
| week | Integers 0-7, 0 and 7 are Sundays |
| command | Ordinary commands, program scripts |
| * | Arbitrary time |
| - | Continuous time range |
| , | Discontinuous interval time |
| / | Specified interval frequency |
[root@localhost ~]# crontab -e crontab: installing new crontab
[root@localhost ~]# crontab -l 50 1 * * * /usr/bin/cp -p /etc/passwd /root/passwd.bak 30 1 */3 * * /usr/bin/tar zcvf /opt/log.tar.gz /var/log/
[root@localhost ~]# crontab -r [root@localhost ~]# crontab -l no crontab for root