Linux crontab is similar to windows task schedulers. Crontab are very useful for routine tasks like scheduling system scanning, daily backups etc. To check Crontab is installed or not, try to execute crontab -l command:
# crontab -l -bash: crontab: command not found
The above error means Crontab is not installed yet, Use below command to install it on your server, this will install required dependencies also:
# yum install cronie
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirror.web-ster.com
* updates: mirror.stanford.edu
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package cronie.x86_64 0:1.4.4-12.el6 will be installed
--> Processing Dependency: dailyjobs for package: cronie-1.4.4-12.el6.x86_64
--> Running transaction check
---> Package cronie-anacron.x86_64 0:1.4.4-12.el6 will be installed
--> Processing Dependency: crontabs for package: cronie-anacron-1.4.4-12.el6.x86_64
--> Running transaction check
---> Package crontabs.noarch 0:1.10-33.el6 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
================================================================================
Package Arch Version Repository Size
================================================================================
Installing:
cronie x86_64 1.4.4-12.el6 base 73 k
Installing for dependencies:
cronie-anacron x86_64 1.4.4-12.el6 base 30 k
crontabs noarch 1.10-33.el6 base 10 k
Transaction Summary
==========================================================
Install 3 Package(s)
Total download size: 114 k
Installed size: 220 k
Is this ok [y/N]: y
Downloading Packages:
(1/3): cronie-1.4.4-12.el6.x86_64.rpm | 73 kB 00:00
(2/3): cronie-anacron-1.4.4-12.el6.x86_64.rpm | 30 kB 00:00
(3/3): crontabs-1.10-33.el6.noarch.rpm | 10 kB 00:00
--------------------------------------------------------------------------------
Total 336 kB/s | 114 kB 00:00
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : cronie-1.4.4-12.el6.x86_64 1/3
Installing : crontabs-1.10-33.el6.noarch 2/3
Installing : cronie-anacron-1.4.4-12.el6.x86_64 3/3
Verifying : crontabs-1.10-33.el6.noarch 1/3
Verifying : cronie-anacron-1.4.4-12.el6.x86_64 2/3
Verifying : cronie-1.4.4-12.el6.x86_64 3/3
Installed:
cronie.x86_64 0:1.4.4-12.el6
Dependency Installed:
cronie-anacron.x86_64 0:1.4.4-12.el6 crontabs.noarch 0:1.10-33.el6
Complete!As per your requirements to add a cron job use the :
# crontab -e
In filesystem crons are saved in file /var/spool/cron/
To list scheduled jobs for current user under Crontab ,we can use:
crontab -l
To view jobs scheduled under other user :
# crontab -u <username> -l