Cron basics

[Hondy]

Hi

I need to run a script once a day at 10am
How do I actually edit the crontab and save it, and what do I need to put in the crontab. I'm using CentOS.

Also do you have to be logged in as the user that created the job for it to run?

Thanks

 

[Edcrosbys]

crontab -e will bring up your favorite editor. Afterwards you will need to put the following line :
0 10 * * * /your/script_name

You do not need to be logged in to have cron run. Cron will run the script as the user you were logged in as when you typed crontab -e. Below is more info about cron. Again, I highly recommend reading man cron.

Each line of CRONTAB has the following structure:
<Minute> <Hour> <Day> <Month> <Day of Week> <Command line>
Position: Values:
Minute 0-59
Hour 0-23
Day 1-31
Month 1-12
Day of week 0-6 (0=Sunday, 1=Monday, ..., 6=Saturday)

 

[Hondy]

ok but if I do crontab -e, it gives me a terminal style window, i have read :qw quits but I can't get it to work.

Then I read that you can go into /var/spool/cron/user and edit it directly with something like gedit.

When I do a crontab -l it shows my job in there like:

59 17 * * * /admin/backup/backup.sh

Assuming that is correct it didn't run at 17:59 as expected, I restarted the crond service beforehand to make sure, but what is going on?

I've had a look at man cron but I'm no better off, it seems its correct but the script doesn't run...

Any ideas?

 

[IPGuru]

I know the Di hard Gurus will frown upon this but I find Webmin makes configuring this type of task very simple
(ducks for cover)

 

[lgarner]

The vi command is ":wq", not ":qw".

The crontab entry looks ok. Is the script executable? Can you run it manually? Does it depend on any environment variables (path, etc)?

 

[Hondy]

ah I got it working, it turns out it was my error.

Is there anything I have to run if the server is rebooted or will it retain it?

Thanks for the suggestion IPGuru

 

[lgarner]

As long as crond is automatically started, there's nothing else needed.