Installing the crontab service in CentOS
Today, when I configured crontab on the test machine, I found that it was not installed, so I had to install one quickly.
CentOS version: 5.7
Procedure
1. Check whether crontab is installed:
Execute the crontab command. If command not found is reported, it indicates that the crontab is not installed.
2. Install crontab
Run yum install-y vixie-cron
3. confirm whether the installation is successful:
Execute crontab-e
4. Check whether Automatic startup is enabled.
Chkconfig -- list crond
5. Start crontab
Service crond start
Detailed records
[Root @ node16 eap_designer] # crontab-e
-Bash: crontab: command not found
[Root @ node16 eap_designer] # yum install-y crontab
Loaded plugins: fastestmirror
Determining fastest mirrors
* Base: centos.ustc.edu.cn
* Extras: centos.ustc.edu.cn
* Updates: centos.ustc.edu.cn
Base | 1.1 kB
Extras | 2.1 kB: 00
Extras/primary_db | 171 kB: 00
Updates | 1.9 kB: 00
Updates/primary_db | 464 kB
Setting up Install Process
No package crontab available.
Nothing to do
[Root @ node16 eap_designer] # yum install-y cron
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* Base: centos.ustc.edu.cn
* Extras: centos.ustc.edu.cn
* Updates: centos.ustc.edu.cn
Setting up Install Process
No package cron available.
Nothing to do
[Root @ node16 eap_designer] # yum install-y crond
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* Base: centos.ustc.edu.cn
* Extras: centos.ustc.edu.cn
* Updates: centos.ustc.edu.cn
Setting up Install Process
No package crond available.
Nothing to do
[Root @ node16 eap_designer] # yum install-y crontab
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* Base: centos.ustc.edu.cn
* Extras: centos.ustc.edu.cn
* Updates: centos.ustc.edu.cn
Setting up Install Process
No package crontab available.
Nothing to do
[Root @ node16 eap_designer] # yum install-y crontabs
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* Base: centos.ustc.edu.cn
* Extras: centos.ustc.edu.cn
* Updates: centos.ustc.edu.cn
Setting up Install Process
Package crontabs-1.10-8.noarch already installed and latest version
Nothing to do
[Root @ node16 eap_designer] # crontab
-Bash: crontab: command not found
[Root @ node16 eap_designer] # cd
[Root @ node16 ~] #
[Root @ node16 ~] #
I checked the information to know that it is not cron, crond, crontab, crontabs, but vixie-cron.
[Root @ node16 ~] # Yum install-y vixie-cron
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* Base: centos.ustc.edu.cn
* Extras: centos.ustc.edu.cn
* Updates: centos.ustc.edu.cn
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package vixie-cron.i386. 1-77.el5_4.1 set to be updated
--> Finished Dependency Resolution
Dependencies Resolved
========================================================== ========================================================== ========================================================== ================
Package Arch Version Repository Size
========================================================== ========================================================== ========================================================== ================
Installing:
Vixie-cron i386 4:4. 1-77.el5_4.1 base 79 k
Transaction Summary
========================================================== ========================================================== ========================================================== ================
Install 1 Package (s)
Upgrade 0 Package (s)
Total download size: 79 k
Downloading Packages:
Vixie-cron-4.1-77.el5_4.1.i386.rpm | 79 kB
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing: vixie-cron 1/1
Installed:
Vixie-cron.i386 4: 4. 1-77.el5_4.1
Complete!
[Root @ node16 ~] # Crontab-l
No crontab for root
[Root @ node16 ~] #
[Root @ node16 ~] # Chkconfig -- list crontab
An error occurred while reading information in the crontab service: the file or directory does not exist.
[Root @ node16 ~] # Chkconfig -- list cron
An error occurred while reading information in the cron service: the file or directory does not exist.
[Root @ node16 ~] # Chkconfig -- list
Anacron 0: off 1: off 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Avahi-daemon 0: Disable 1: Disable 2: Disable 3: Enable 4: Enable 5: Enable 6: Disable
Avahi-dnsconfd0: Close 1: Close 2: Close 3: Close 4: Close 5: Close 6: Close
Crond 0: off 1: off 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Gpm 0: Disable 1: Disable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Haldaemon 0: Disable 1: Disable 2: Disable 3: Enable 4: Enable 5: Enable 6: Disable
Iscsi 0: Disable 1: Disable 2: Disable 3: Enable 4: Enable 5: Enable 6: Disable
Iscsid 0: Disable 1: Disable 2: Disable 3: Enable 4: Enable 5: Enable 6: Disable
Jexec 0: Enable 1: Enable 2: Enable 3: Enable 4: Enable 5: Enable 6: Enable
Kudzu 0: Disable 1: Disable 2: Disable 3: Enable 4: Enable 5: Enable 6: Disable
Lvm2-monitor 0: off 1: Enable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Mcstrans 0: Disable 1: Disable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Messagebus 0: Disable 1: Disable 2: Disable 3: Enable 4: Enable 5: Enable 6: Disable
Multipathd 0: Close 1: Close 2: Close 3: Close 4: Close 5: Close 6: Close
Mysql 0: Disable 1: Disable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Netconsole 0: Close 1: Close 2: Close 3: Close 4: Close 5: Close 6: Close
Netfs 0: Disable 1: Disable 2: Disable 3: Enable 4: Enable 5: Enable 6: Disable
Netplugd 0: Close 1: Close 2: Close 3: Close 4: Close 5: Close 6: Close
Network 0: Disable 1: Disable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Rawdevices 0: Disable 1: Disable 2: Disable 3: Enable 4: Enable 5: Enable 6: Disable
Rdisc 0: Close 1: Close 2: Close 3: Close 4: Close 5: Close 6: Close
Restorecond 0: Disable 1: Disable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Sshd 0: Disable 1: Disable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Syslog 0: Disable 1: Disable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Tcsd 0: Close 1: Close 2: Close 3: Close 4: Close 5: Close 6: Close
Xfs 0: Disable 1: Disable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
[Root @ node16 ~] # Chkconfig -- list crond
Crond 0: off 1: off 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
[Root @ node16 ~] # Service crond
Usage:/etc/init. d/crond {start | stop | status | reload | restart | condrestart}
[Root @ node16 ~] # Service crond status
Crond stopped
[Root @ node16 ~] #
[Root @ node16 ~] #
[Root @ node16 ~] # Service crond start
Start crond: [OK]
[Root @ node16 ~] # Service crond status
Crond (pid16932) is running...
[Root @ node16 ~] #
After completing the above basic work, let's see how to use crontab to regularly execute the PHP script:
(1) I create the test. php file under/root. The content is as follows:
- <? Php
- #! /Usr/bin/php-q
- Echo date ('Y-m-d H: I: s'). "from http://www.phpddt.com \ n ";
- ?>
Note: You can use whereis php to find the location of the php Execution file.
Enter php-q test. php In the command line to test whether the PHP program you wrote can run normally (2). Then crontab-e writes the following shell:
- * ***/Usr/bin/php-f/root/test. php> test. log
Note: test. php must be an executable file: chmod + x test. php test results are normal. Of course, you can use crontab-e to continue adding tasks. Under/var/spool/cron, you can see a root file. We can see that you can use tail-f/var/log/cron to observe the log. You can also use ps-aux | grep cron to view all processes.
