"The directory sites/default/files is not writable" error I am trying to install drupal 8.1 on a CentOS linux machine as root user. 
I am getting "The directory sites/default/files is not writable." error. Before that, I had to manually create the sites/default/files folder. I have even changed the permission to 777 for all files and folder in "sites" and its sub folders and 'root' is owner of all files and folders/subfolders. 


  -rwxrwxrwx. 1 root root  5997 Apr 27 05:28 default.services.yml
  -rwxrwxrwx. 1 root root 29105 Apr 27 05:28 default.settings.php
  drwxrwxrwx. 2 root root     6 Apr 27 05:45 files
  -rwxrwxrwx. 1 root root 29105 Apr 27 05:40 settings.php


How can I fix this issue?
Install the drupal using virtual host, it will be help to manage all the permissions. Here i'm giving an example of a virtual host file with some permissions which might help you install the site. 



    &lt;Directory "/var/www/html/mysite"&gt;

    Options Indexes FollowSymLinks Includes ExecCGI
        AllowOverride All
        Require all granted
        Allow from all

    &lt;/Directory&gt;

    ServerName mysite.local
    ServerAlias www.mysite.local
    DocumentRoot /var/www/html/mysite
    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

&lt;/VirtualHost&gt;