Обновление 12.04.4 LTS до 14.04 LTS завершается неудачно на Pandaboard

Я пытаюсь обновить 12.04.4 LTS до 14.04 LTS на Pandaboard. Обновление через do-release-upgrade -d завершается неудачно с

Fetched 0 B in 0s (0 B/s)                                                      
Hit http://ports.ubuntu.com trusty Release.gpg                                 
Hit http://ports.ubuntu.com trusty-security Release.gpg                        
Hit http://ports.ubuntu.com trusty-updates Release.gpg                         
Hit http://ports.ubuntu.com trusty-backports Release.gpg                       
Hit http://ports.ubuntu.com trusty Release                                     
Hit http://ports.ubuntu.com trusty-security Release                            
Hit http://ports.ubuntu.com trusty-updates Release                             
Hit http://ports.ubuntu.com trusty-backports Release                           
Fetched 0 B in 0s (0 B/s)                                                      

Error during update 

A problem occurred during the update. This is usually some sort of 
network problem, please check your network connection and retry. 

W:Failed to fetch 
http://ports.ubuntu.com/ubuntu-ports/dists/trusty/Release Unable to 
find expected entry 'main/binary-armel/Packages' in Release file 
(Wrong sources.list entry or malformed file) 
, W:Failed to fetch 
http://ports.ubuntu.com/ubuntu-ports/dists/trusty-security/Release 
Unable to find expected entry 'main/binary-armel/Packages' in Release 
file (Wrong sources.list entry or malformed file) 
, W:Failed to fetch
.... 
, E:Some index files failed to download. They have been ignored, or 
old ones used instead. 

, нажав http://ports.ubuntu.com/dists/trusty/ в браузере. Я вижу, что armel действительно отсутствует. Поэтому мне интересно, как я могу обновить с 12.04.4 до 14.04 на этой плате.