Fatal error: $CFG->dataroot is not writable, admin has to fix directory permissions! Exiting

Solution : 

How to allow your moodle data write permission.
Please follow these steps
For that please go to /var/www/moodledata or if any path where you defined the moodle data then just paste this command

chmod 0777 /var/moodledata
chown www-data:www-data /var/moodledata

moodle folder permissions
moodledata not writable
moodle parent directory is not writable
dataroot location is not secure
moodle installation
moodle dataroot
moodledata permissions
invaliddatarootpermissions