※ cron is a linux under the regular implementation of the tool, you can run the job without the need for manual intervention.
Because Linux Cron is a built-in services, but it does not auto-up, you can start with the following methods to close this service:
service crond start // Start Service
service crond stop // shut down service
service crond restart // restart the service
service crond reload // reload the configuration
Below this is the command timed tasks:
crontab -u // set a user's cron service, usually root user needs this parameter when executing this command
crontab -l // set out in detail the contents of a user cron services
crontab -r // not delete a user's cron service
crontab -e // edit a user's cron service
For example, set the root view their own cron: crontab -u root -l
For another example, root want to delete the cron setting fred: crontab -u fred -r
When editing cron service, edit the contents of some of the formats and conventions, enter: crontab -u root -e
※ 1, linux work scheduling is divided into the following two categories:
Work performed by the system: The system periodically work to be performed, such as data backup system, clear the cache
Work performed by a person: a user work to be done on a regular basis, such as every 10 minutes to check the mail server for new letter, which work by each user their own settings.
2.cron file syntax:
Minute hour day Monday user command
0-59 0-23 1-31 1-12 0-6 root command?
3. Remember the meaning of several special symbols:
"*" Representatives within the range of numbers,
"/" Stands for "every"
"-" represents the numbers from one to a certain number,
"" Several separate discrete digital
※ available crontab -e command to edit, edit the corresponding user / var / spool / cron cron the file, you may directly modify / etc / crontab file;
Example periodic task set:
- Open daily 7:00 sshd
2. Eleven pm every day to close sshd
3. emptied once every five days notice FTP server directory / var / ftp / pub
4. six or seven points a week and a half, restart the httpd service
5. weekly one hundred thirty-five 17:30, packing backup / etc / httpd directory
6. The backup log file / var / log / messages
( Common kernel message log information and various applications, including start, I / O error, network error, program failure, etc.)
7. The backup log file / var / log / cron
(Crond time information periodically scheduled task generated)
8. backup log file / var / log / dmesg
(Various times during boot program information)
9. backup log file / var / log / maillog
(Entering or outgoing e-mail system activity)
10. The backup log file / var / log / lastlog
(Each user has recently logged events)
11. The backup log file / var / log / secure
(User authentication security-related time information)
12. The backup log file / var / log / wtmp
(Each user login, logout and system startup and shutdown events)
13. backup log file / var / log / btmp
(Failures, incorrect login attempts and validation events)
Packing compression / etc 14. 24 points every night / passwd / etc / shadow / etc / group
/etc/gshadow /etc/gpasswd
15. Monday of every five minutes lists the disk usage
16. The daily at 8:30 and the Internet time synchronization time synchronization server pool.ntp.org
