Example and common techniques for setting parameters of Crontab Timing task in Linux system

Under the circumstances, we operate and operation of the VPS, the server may be used to crontab timing task configuration, such as the timing of the restart of the server, scheduled backup data and other operations using or more. This is inseparable from the use of the crontab command of the task configuration, in this article, the old left will be a more complete crontab command to use the method and commonly used instance operations.

From the above figure, we can actually see crontab specific usage. A total of 6 paragraphs, the first 5 marked timed time set, the next indicator of the path of the file is timed to execute.

First, crontab installation

Generally we use the CentOS or the Debian release version with the crontab timing software support, if the system does not support, we only need to install through the following corresponding.

1, CentOS installation crontab

The code is as follows	Copy Code
#安装Crontab Yum Install Vixie-cron Crontabs #设置开机启动Crontab Chkconfig Crond on #启动Crontab Service Crond Start

2, Debian installation crontab

The code is as follows	Copy Code
#安装Crontab Apt-get Install cron #重启Crontab /etc/init.d/cron restart

Make sure that the system is installed and running in effect before it can be related to the settings.

Second, timed task cases

1. * * * * updatedb

Update the database once every hour and 35 minutes.

2, */5 * * * * */usr/local/bin/diskusage.sh

Run diskusage.sh files every 5 minutes.

3, 25,50 1 * 2/usr/local/bin/diskusage.sh

1:50am Execution documents per Tuesday

4 3,6,9,12 */usr/local/bin/diskusage.sh

3, 6, 9, December, tenth day of the Year, 2 o'clock in the afternoon.

5 * * mon,wed,fri/usr/local/bin/diskusage.sh admin@laozuo.org

Execute scripts every Monday, five 9 o'clock in the afternoon

6, */5 * * * 1-5/usr/local/bin/diskusage.sh

Monday to Friday, executed every five minutes.

Third, System scheduling

The code is as follows	Copy Code
/etc/cron.d/etc/cron.daily/etc/cron.hourly/etc/cron.monthly/etc/cron.weekly

If our root directory is executing the backup.sh backup command, use the above script to directly replace the/etc/cron.weekly directory.

Level setting of timing plan

When we operate, each user can edit, view, and delete the crontab timing profile. If the root user needs to change the crontab file, the '-u ' option must be added to specify the user name.

1, edit crontab file users Laozuo time, we can use the command:

Crontab-u LAOZUO-E

2, remove the Laozuo user's timing setting

Crontab-u Laozuo-r

3, view Laozuo scheduled task settings file

Crontab-u laozuo-l

Four, loading crontab from the file

In addition to manually editing a timed file, we can also load the file into a timed file.

The code is as follows	Copy Code
Cat/root/mycronjobs.txt * * 7/bin/sh/root/server-backup.sh * * * */bin/sh/root/check-user-quota.sh

We need to upload the edited Mycronjobs.txt timed task files to the directory before they can be executed.

The code is as follows	Copy Code
Crontab/root/mycronjobs.txt

Check validation with this command.

The code is as follows	Copy Code
Crontab-l * * 7/bin/sh/root/server-backup.sh * * * */bin/sh/root/check-user-quota.sh

Here we can check if the timed file exists.

Add SELinux security Options

The code is as follows	Copy Code
Crontab-s/root/mycronjobs/my.txt selinux_role_type=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 * * 7/bin/sh/root/server-backup.sh * * * */bin/sh/root/check-user-quota.sh

VI. Delete Timed task work

The code is as follows	Copy Code
[Root@linux ~]# Crontab-l * * 7/bin/sh/root/server-backup.sh * * * */bin/sh/root/check-user-quota.sh [Root@linux ~]# Crontab-r [Root@linux ~]# Crontab-l No crontab for Root

We first use-l to view the current scheduled task, then use-R to delete, and then check that there are no task options.

Summary, the above 6 steps and methods, that is, we commonly used crontab timing file configuration commonly used, we will use a lot of backup and timed to start, according to our actual need to adjust the time.