Configuration and description of the Linux Scheduling task tool cron

A summary of the planning tasks

The task of planning is to perform the work that has been planned at the agreed time, which is the superficial meaning. In Linux, we often use the Crond server to do this work. A cron server can perform a specific service based on the time of the profile appointment. For example, we can make an appointment in the configuration file 4 O ' Day in the morning, to the httpd server reboot, this is a scheduled task. Now let's talk about Cron:

Second, Cron;

In a Linux system, the scheduling task is typically done by cron, and we can set the cron to start automatically when it is powered on. When Cron starts, it reads all of its configuration files (the global profile/etc/crontab, and the scheduled task profile for each user), and then Cron invokes the task on time according to the command and execution time.

1, the installation and start-up of Cron;

In general, Cron is installed by default, we have to learn to see if the package has been installed;

(1) in Redhat or fedora, such as the installation of the RPM package management system;

Determine if the system has a cron-related package installed

Fedora 5.0 system situation;

Other versions of Fedora and Redhat systems are similar to this;

[Root@localhost ~]# Rpm-qa |grep cron

Vixie-cron-4.1-54.fc5

anacron-2.3-36.1

crontabs-1.10-7.1

Where the Vixie-cron package is a cron main program, you can learn about it in the following order, with other packages being the same;

[Root@localhost beinan]# rpm-ql Vixie-cron

The Crontabs package is a program used to install, uninstall, or enumerate the tables used to drive the cron daemon. The cron daemon checks the crontab file to see when a specified command is scheduled to execute. If the commands are already scheduled, the daemon executes them. Learn what Crontabs packages are installed, and use the following commands;

[Root@localhost beinan]# rpm-ql Crontabs

If it is not installed, you can install it from the CD-ROM package with cron lettering.

[Root@localhost ~]# RPM-IVH vixie-cron-4.1-54.fc5*

[Root@localhost ~]# RPM-IVH crontabs*

can also use Yum to install online;

[Root@localhost ~]# Yum Install Vixie-cron

[Root@localhost ~]# Yum Install Crontabs

(2) installation in the Slackware system;

The cron package in Slackware is Dcron and you can find it on the CD to install it;

See if the Dcron package has been installed, so you can view it. Here you can list the detailed installation of the package;

[Root@localhost ~]# more/var/adm/packages/dcron*

If it is not installed, use the following command to install it. Locate the Dcron software package in the first installation disk;

[Root@localhost ~]# installpkg dcron*.tgz