I found :
Cannot change permissions for path "/var/www/html/ pub/media/captcha/base" Warning!chmod(): Operation not permitted in support_report.log.
I have given /var/www/html/ pub/media/captcha permission 777 and ownership root. But the problem still appears.
How to deal with this issue?
For best security practices, the owner of the Magento filesystem should be one user, and the user that PHP or the webserver runs as a different user.
So for example, if you have a user "mySiteUser" and PHP runs as the user and group "www-data" (httpd or apache for RedHat/CentOS/Fedora); then your /var/www/html/<site_name>/pub/media would be owned by mySiteUser and the group would be "www-data": chown -R mySiteUser:www-data /var/www/html/<site_name>/pub/media.
That's not the only folder that should be set up like this. There are others. I suggest you read through the Magento DevDocs on file permissions for more info: http://devdocs.magento.com/guides/v2.0/install-gde/prereq/file-sys-perms-over.html and http://devdocs.magento.com/guides/v2.0/install-gde/prereq/file-system-perms.html
