Do you use Moodle 1.9.x or 2.0.x?
Do you run your own server or do you have an internet service provider doing this?
I have my own server with linux11.1
The best way is to ask a friend in Sanaa to help you with the cron and Linux. Perhaps at the university?
Here are some Moodle Installations in Yemen. Perhaps they can give you a help
This is not a Moodle problem per se and there's tons of advice on the web. Exactly how you do it depends on your situation. For example, a simple setup is to use a mysql backup script (you end up with a zip file), taking a zip of moodledata and then sending them all to some off-site location using 'rsync'. You can also obtain dedicated backup software too.
"a simple setup is to use a mysql backup script" ... ??????
for innoDB????? which backup script?
moodledata is a simple rsync matter ... or... go get some dedicated backup software to suit your local situation.
This is really basic system administration stuff that you need to know to run a production server - before you even get to running Moodle. There's mountains of help online but it does depend on your particular setup and requirements what route is best. Simply syncing your data to another machine at a remote location is often the easiest thing and fairly safe (as long as you test the backup integrity regularly).
sum advocatus diaboli
Don´t you think you are are a little snotty to new moodle-admins!
I gave you some pointers and clearly you can't be bothered to look them up either.
If you are going to run a production Moodle site or ANY public server (assuming you are) then you have to take some responsibility for acquiring basic system administration skills. This is even before you get to running Moodle. This will include making sure your system is secure, is regularly updated and you find a backup regime that suits your needs. It's not all that difficult but it's basic knowledge you need to have.
You should see the number of people in these forums who ask "I tried to do X,Y and Z now my Moodle site is broken". When asked if they have a backup they don't and so they are going to have a VERY bad day.
If you want some more reading, I use this script for mysql backups:
We then backup the resulting files along with the moodledata files (and lots of other stuff) using rsync over ssh. There's loads of info but here's one..
We backup to a specific backup server and then back that up (slightly less regularly) to another backup server at a remote location.
OR... you could use the Moodle scheduled backup to backup courses to a specific location and rsync that. This is not much use a disaster recovery backup as you would need to restore every course (and backup isn't all that reliable in the first place)
Is this more helpful and non-snotty now?
I have heared about something called cron
what is it for
Moodle uses it to do things like send out forum emails and run scheduled backups. (further - non Moodle specific - reading http://en.wikipedia.org/wiki/Cron)