ps -ef | grep cron
If it is not running at the startup, start the daemon
service crond start
and set it to start at the system startup.
chkconfig crond on
Then you can do scheduling. If you view the '/etc/crontab' file you can get all the information needed to provide to automate an execution of a command.
SHELL=/bin/bash PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root HOME=/ # For details see man 4 crontabs # Example of job definition: # .---------------- minute (0 - 59) # | .------------- hour (0 - 23) # | | .---------- day of month (1 - 31) # | | | .------- month (1 - 12) OR jan,feb,mar,apr ... # | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat # | | | | | # * * * * * user-name command to be executedYou can run these commands as ether root or a normal user. Type 'crontab -e' to add/edit crons. If you type 'crontab -e' as a normal user, it will open a user specific cron list. If you need to schedule a task which require admin privileges, you need to login as root and type the 'crontab -e'.
Do a task in every 15 min.
*/15 * * * * root /usr/bin/command
0,15,30,45 * * * * root /usr/bin/command
There are some more keywords you can when scheduling tasks. Those are;
@reboot @yearly or @annually @monthly @weekly @daily or @midnight @hourly
You can use it like this;
You can modify a command to log the output of the execution to a specific file by;
@reboot /root/scripts/mystartup.sh >>/var/log/mystartupcron.log 2>&1
Note: Try to use absolute paths when editing commands in crontab.