Can you provide a bit more information. Unfortunately what you've shared is not enough to determine what's occurring.
1.) How are you uploading files? SFTP? A web app?
2.) If this is a website are you using a platform like WordPress? Is it a PHP site? A Rails site?
Since WordPress on LAMP (Linux Apache MySQL PHP) is the most common stack I'll address that here:
PHP has some fairly small default max filesize settings for uploads. This can be changed by editing your php.ini file. On Ubuntu this file can be found in
In this file there are two directives you will want to change to increase the upload size:
maxpostsize - This tells php what the largest request it will accept as a POST. This is the method used when uploading files so it will need to be set larger than the largest file you plan to upload.
uploadmaxfilesize - This is more specific and refers to the maximum size for any file that is uploaded using php.
Once these two settings are changed you will need to restart Apache
service apache2 restart for the changes to take effect.