mysqldump to crontab

I'm not sure about the size of the command line. I would create a small shell script with the command you want to call mysqldump and place that script in cron.daily (weekly/montly/ etc)

and you would also be able to the script in crontab file with a shorter command

Also, I would check if the user you are assigning can has enough permissions (like permission to write the output file )

Can you elaborate how is not working?

On personal experience I was hit by cron running as a different user that assumed. You may want to try

su -l USER -c mysqldump --default-character-set=utf8...

a different problem I also had was that the first run took longer than the cron interval, in fact short-circuiting the backup. You may want to run the first backup from the command line and check how long it takes.

Even if the command runs as the same user in crontab as in real life, the environment may be initialized differently when cron invokes the command. For example, $PATH may be missing the directory that contains mysqldump.

Try this script from Sourceforge: AutoMySQLBakcup, it works great, is easy to setup and maintain.