crond Service Management
1 . Re- start the crond service
[root@hadoop101 ~]# service crond restart
centOS7是 systemctl restart crond
crontab scheduled tasks set
1. The basic syntax
crontab [ options ]
2 . Option Description
Table 1-46
| Options |
Features |
| -e |
Edit crontab regular tasks |
| -l |
Query crontab task |
| -r |
Delete all the current user's crontab tasks |
3. Parameter Description
[root@hadoop101 ~]# crontab -e
( 1 ) into the crontab editing interface. It will open vim to edit your work.
* * * * * Task execution
Table 1-47
| project |
meaning |
range |
| The first " * " |
Among the first few minutes of one hour |
0-59 |
| The second " * " |
The first few hours of the day |
0-23 |
| The third " * " |
The first day of the month among the |
1-31 |
| The fourth " * " |
The first few months of the year |
1-12 |
| The fifth " * " |
The week of the week |
0-7 ( 0 and 7 represent Sunday) |
( 2 ) special symbols
Table 1-48
| Special symbols |
meaning |
| * |
Representatives at any time. For example, the first " * " represents one hour are executed once meant every minute. |
| ， |
On behalf of discontinuous time. For example, " 0 8,12,16 * * * Commands", on behalf of the daily 8 Dian 0 points, 12 Dian 0 points, 16 Dian 0 Fen command is executed once |
| - |
It represents the continuous time frame. For example, " 05 * * 1-6 command" on behalf of Monday to Saturday morning 5 Dian 0 execute command points |
| */n |
Representative of how often executed once. Such as " * / 10 * * * * Commands", on behalf of every 10 minutes to execute the command again |
( 3 ) specific command execution time
Table 1-49
| time |
meaning |
| 4522 * * * command |
At 22 is point 45 Run minutes |
| * 017 * 1 command |
Week 1 of . 17 point 0 different executive command |
| 05 1,15 * * command |
Monthly 1 numbers and 15 numbers Lingchen 5 Dian 0 different executive order |
| 404 * * 1-5 Command |
Monday to Friday morning 4 Dian 40 different executive order |
| * / 104 * * * command |
Daily morning . 4 points every 10 minutes to perform a command |
| 0 0 1,15 * 1 command |
Monthly 1 numbers and 15 numbers, each week 1 of 0 Dian 0 Fen will execute the command. Note: The day of the week and number of several best not to appear because they are defined in days. Very easy for administrators to confusion. |
4. Case practical operation
( 1 ) every 1 minute /root/bailongma.txt to add a file 1 the number 1
*/1 * * * * /bin/echo ”11” >> /root/bailongma.txt