I take it you have created a new user on initial setup and granted admin privileges to the new user? somewhere in line with this guide
If you have try this…
Login with created user credentials:
ssh username@ip address`
Once logged in type this:
sudo bash
Enter your password, this should then show you in control as root user (root@yourdropletname:~#) Next enter this:
nano /etc/ssh/sshd_config
Search for a section where it says “PermitRootLogin” and if set to ‘no’ change to 'yes’
Press 'Cntl+X’ to exit then 'Y’ then 'ENTER’ to save.
Type:
reload ssh
Now root (<—user) login through SFTP to change you php.ini file inside etc/php5/apache2/ to suit. Once this has been edited and saved go back to the nano /etc/ssh/sshd_config
step and change back 'PermitRootLogin’ to 'no’ and remember to reload ssh
again.
Finally use this command:
sudo service apache2 restart
Hopefully that should do it! Worked for me : )

by Justin Ellingwood
When you start a new server, there are a few steps that you should take every time to add some basic security and set a solid foundation. In this guide, we'll walk you through the basic steps necessary to hit the ground running with Ubuntu 14.04.