I find out how to activate the module; see: http://help.openerp.com/question/42974/how-to-install-a-module/?answer=42980#post-id-42980

I unzipped the addon on the server /usr/share/pyshared/openerp/addons but I couldn't find it in modules to activate it!!!

I tried another way. [1] Activated "Technical Features" for admin user [2] Settings->Technical->UserInterface->MenuItems [3] Edit "Settings/Modules" [4] Added submenu called "Import" with "Action: ir.actions.act_window" and "Module Import" [5] Saved the changes and refreshed the window (I can see a new submenu called "Import") [6] Settings->Modules->Import [7] Selected the downloaded zip file (attachment_size_limit-7.0.1.0.zip) then clicked "Import Module" [8] I got the following error message

Can not create the module file: /usr/lib/pymodules/python2.7/openerp/addons/attachment_size_limit.zip! BTW, /usr/lib/pymodules/python2.7/openerp/addons owned by openerp user and group! I tried to restart OpenERP server sudo service openerp restart but I got same error message on import module!!!

Just for testing purpose could you add full rights on addons folder? chmod 777

@Youri I did it... but it didn't affect.