Support

Based on the information you provided us in ticket 18196, your problem can be caused by:
- A small upload or post size, which you increased to 8Mb
- An unwriteable or inexistent PHP temporary directory
- An unwriteable Joomla! temp directory

Since you have made changes to your server's php.ini and considering that you said you are your own host you should know that changes do not take effect unless you restart your web server. More specifically:

• If you are using PHP as a module (default configuration on most Linux distros) you must restart the web server. The PHP configuration is only read when the PHP module (mod_php) initialises at server start.
• If you are using PHP as a CGI script (including suPHP) then a php.ini inside your site's administrator directory or PHP configuration variables in your .htaccess take immediate effect without server restart.
• If you are using PHP as a FastCGI script you need to restart PHP-FPM (PHP FastCGI process manager)

The information above is well beyond the scope of our support and provided as a courtesy. Since you are your own host you should know this information and have already acted upon it.

Moreover, 3.8 is not the latest release. The latest release at the time of this writing (and when you posted your ticket) is 3.9.1.

Additionally, please note that the extensions installer (com_installer) is a core component shipped with Joomla!, using core libraries shipped with Joomla!. Our code only runs at the very end of the installation, when the post-installation message is about to be displayed. At the point you get the error you have a problem with Joomla! itself. We do not provide support for third party software, including Joomla! itself. We try to help with installation issues, but it's not in the scope of our support.

Recapitulating, the problem you have does seem to be a server issue. Admin Tools is a small package (less than 2Mb) which is exactly why it caused no problems during installation. Akeeba Backup is a big package (2.75Mb), bigger than the default 2Mb limit in php.ini files shipped with most distributions. Joomla! itself warns you about this (see Extensions, Manage Extensions, Warnings) and recommends you to do the same thing Davide asked you to do, in cooperation with your host. In the end of the day your problem arises from you attempting to be your own host but lacking the proper knowledge to manage your own server. It's understandable, but we can't help you with that. This reply which discusses server administration issues and provides you with advice on solving them is well beyond the scope of our support as agreed in our ToS. Unfortuantely I cannot help you any more than that. Any further assistance would be equivalent to personalised consultancy on an a topic (server management) unrelated to our software.

I hope that you find this information useful and now understand why we had to close your ticket.