Login form root
and check system date, and run crontab command to schedule job
#date
#crontab –e
Field
Value
minute 0–59
hour Based
on a 24-hour clock; for example, 23 = 11 P.M.
day of month 1–31
month 1–12,
or jan, feb, mar, etc.
day of week 0–7;
where 0 and 7 are both Sunday; or sun, mon, tue, etc.
command The
command you want to run
11 5
3 5 * ls
This
above line runs the ls command every May 3 at 5:11 A.M. The asterisk in the day
of week column simply means that it does not matter what day of the week it is;
crontab still runs the ls command at the specified time.
#crontab
–e
50
21 14 02 * ls > /dev/tty2
In real life you do not have to restart cron
every time you make a change because cron always checks for changes, But so far
exams concern we suggest you to restart cron whenever you made change.
#service crond restart
Example:#
# Minute Hour Day of Month Month Day of Week Command
# (0-59) (0-23) (1-31) (1-12 or Jan-Dec) (0-6 or Sun-Sat)
0 2 12 * 0,6 /usr/bin/find
This
line executes the "find" command at 2AM on the 12th of every month
that a Sunday or Saturday falls on.
2.0
Examples
3.0
Setting Up
cron for Users
Each user can use the crontab command to create and manage cron jobs
for their own accounts. There are four switches associated with the crontab
command:- -u user Allows the root user to edit the crontab of another specific user.
- -l Lists the current entries in the crontab file.
- -r Removes cron entries.
- -e Edits an existing crontab entry. By default, crontab uses vi.
Two
files are used to control the behavior of crond daemons
- /etc/cron.allow If present then only users those name are in this file can use crond daemons
- /etc/cron.deny If present then only user those name are in this file will not be able to use crond daemons apart from these user all other can use cron daemons
- If both files are not present then only root can access cron daemons
No comments:
Post a Comment