Well the only reason I am posting this is because this is a top hit on google when searching how to root the LG Optimus. I went through alot of frustration trying to get it done but here is how I found on how to do it. ( I have LG Optimus L9 p76920f version 4.1.2)
First you need the 4shared app ( found on google store) and download LGpwn (found on 4shared not in google store.) With the LGpwn app you can root the phone with no PC. Here is a video I saw on how to do it . (
Root LG Optimus L9 No PC! - YouTube ) Just follow what the person does by the book and it should work.
The reason I wanted to root was to transfer apps to my external sd card which is a function the developers took off for the phone. I had a surprisingly hard time trying to find an app to transfer my apps. I finally used the Link2SD app found in the google store. For this app to work you need to have the phone rooted and your sd card partitioned which was the hard part. I found this website on how to do it with the program mini tool since it was a bit technical (
How to Partition SD Card and Use Link2SD in any Android Phone with Screenshots )
After that everything should work. Note: I had trouble initially installing the LGpwn first due to an insufficient memory error even though I had enough internal memory. All I did in the end was clicking factory reset on my phone and it worked.(google saved all my contacts and apps)