/ Sbin / service crond start / / start service
/ Sbin / service crond stop / / close service
/ Sbin / service crond restart / / restart services
/ Sbin / service crond reload / / reload the configuration
You can also start the service automatically when the system starts:
In the / etc / rc.d / rc.local added at the end of this script:
/ Sbin / service crond start
Cron is now inside the service has been in the process, we can use the service of, Cron service provides the following interfaces for your use:
1, directly edit the crontab command
cron service providers to set the cron crontab command service, the following are some of the parameters of this command and description:
crontab-u / / set a user's cron service, usually root user running this command, this parameter needs
crontab-l / / a user cron service listed the details of
crontab-r / / remove a user's cron service
crontab-e / / edit a user's cron service
For example, set the root to see your cron: crontab-u root-l
For another example, root to delete the cron setting fred: crontab-u fred-r
When editing the cron service, edit the contents of some of the formats and conventions, enter: crontab-u root-e
Enter vi edit mode, edit the content must meet the following format: * / 1 * * * * ls>> / tmp / ls.txt
The first part of this format is the time set, the back part of the command to execute if the command to execute too many, you can write these commands inside a script, then here you can directly call the script, and call when I remember to write the full path to the command. Time setting we have some agreement, on behalf of the previous five * number five figures, the range and number of meanings are as follows:
Week (0-6) / / 0 for Sunday
In addition there are several numbers is a special symbol and "-",",",* "*","/" behalf of all the range of numbers, "/" represents the meaning of each "* / 5 "said the five units," - "represents a number from a number to," "separated a few discrete numbers. The following few examples illustrate the problem:
6 o'clock every morning
0 6 * * * echo "Good morning.">> / Tmp / test.txt / / Note that simply echo, not see any output from the screen, because the cron output to email to any mailbox of root.
Every two hours
0 * / 2 * * * echo "Have a break now.">> / Tmp / test.txt
11 pm to 8 am every two hours between the morning and eight
0 23-7/2, 8 * * * echo "Have a good dream:)">> / tmp / test.txt
4th of every month and every week the morning of Monday to Wednesday 11
0 11 4 * 1-3 command line
January 1, 4:00 am
0 4 1 1 * command line
Every time you edit a user's cron settings, cron automatically in / var / spool / cron to generate a file with the same name as the user, this user information recorded in the cron file, this file can not directly edit , and can only use the crontab-e to edit. cron is started every time a bell read this file to check whether to execute the command inside. This file is modified so no need to restart the cron service.
2, edit / etc / crontab cron configuration file
cron service not only to read once per minute / var / spool / cron all the files, but also read an / etc / crontab, so we can configure this file using cron service to do something. Use crontab configuration for a user, and edit / etc / crontab for system tasks. This file format is:
SHELL = / bin / bash
PATH = / sbin: / bin: / usr / sbin: / usr / bin
MAILTO = root / / If an error occurs, or a data output, data as e-mail sent to this account
HOME = / / / the user running path, here is the root directory
01 * * * * root run-parts / etc / cron.hourly / / hourly / etc / cron.hourly the script
02 4 * * * root run-parts / etc / cron.daily / / perform daily / etc / cron.daily script within
22 4 * * 0 root run-parts / etc / cron.weekly / / execute each week / etc / cron.weekly the script
42 4 1 * * root run-parts / etc / cron.monthly / / month to perform the / etc / cron.monthly the script
Attention to "run-parts" of this argument, if this parameter is removed, then later you can write a script to run the name of the folder name rather than a.
* * * * * Command
Time-moon week command
Section 1 of minutes from 1 to 59 per minute with a * or * / 1 means that the first two hours of 1 to 23 (0 0)
Column 3 represents the date from 1 to 31
Section 4 of the month from 1 to 12
Section 5 identifies the number of weeks 0 to 6 (0 for Sunday)
Section 6 of the command to run
Some examples of the crontab file:
30 21 * * * / usr / local / etc / rc.d / lighttpd restart
The above example that night 21:30 to restart lighttpd.
45 4 1,10,22 * * / usr / local / etc / rc.d / lighttpd restart
The above example shows the monthly 1,10,22 Day 4:45 to restart lighttpd.
10 1 * * 6,0 / usr / local / etc / rc.d / lighttpd restart
The above examples show every Saturday, Sunday 1:10 to restart lighttpd.
0,30 18-23 * * * / usr / local / etc / rc.d / lighttpd restart
The above example indicates that every day 18: 00 to 23:00 every 30 minutes between restart lighttpd.
0 23 * * 6 / usr / local / etc / rc.d / lighttpd restart
The above example that every Saturday the 11: 00 pm to restart lighttpd.
* * / 1 * * * / usr / local / etc / rc.d / lighttpd restart
Lighttpd restart every hour
* 23-7/1 * * * / usr / local / etc / rc.d / lighttpd restart
11 pm to 7 am, between every hour restart lighttpd
0 11 4 * mon-wed / usr / local / etc / rc.d / lighttpd restart
Monthly on the 4th and Monday to Wednesday 11:00 to restart lighttpd
0 4 1 jan * / usr / local / etc / rc.d / lighttpd restart
January 1 to 4:00 lighttpd restart
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