Hello,

We have a custom application on our LAMP server for managing websites, so I'm running into a permissions issue during the component install.

It's unable to create any of the directories for the program. I've tried setting directory permissions for user "apache", and even temporarily giving everyone full write access to the joomla tree, but I get the same errors each time:

Unable to create the directory '/home/479_1/portal/multisites'.
This is a symptom that JMS has not enough rigths to proceed with the installation and probably will also failed when installing the patches.
Check the directory and files permission.

A pretty basic error, I'm embarrassed to even have to post this, but I'm not sure which user it's trying to run as to do the install.

Have you tried to increase the permisson of all your Joomla in using a chmod 777 or simply create the directory multisites manually to which you will put a chmod 777.

When you have a permissoin problem, you can also try solve it with the standard Joomla FTP Layer. See tutorial step 15 that may help you.
When using the FTP layer, in fact the installation is perform using the FTP login and password that you specify in the standard Joomla Global Configuration.