by Séverin Terrier.
Hello,
As already explained in french forum, i've used the third solution, by adding a test in moodle/backup/util/helper/backup_cron_helper.class.php. The line 145 is now :
|| ($rundirective == self::RUN_IMMEDIATELY && $backupcourse->courseid != 1) );
And all my backups are OK
Only course 1 (main page) isn't backuped, but it's not really a big problem for me.
The only problem : nextstarttime has been automatically modified by the script (like for all other courses). So, to avoid making backup next time, i've defined a specific cron to modify each day the nextstarttime for course 1, late in the futur. It should so be definetly OK
Séverin