How to update environment on Debian(Developer)

Debian version: latest version that download from bellow link:

    https://builds.96boards.org/releases/dragonboard410c/linaro/debian/16.02/

When running the Developer Debian-based image,
I can’t update my environment with commands such as:

sudo apt-get update

Error info:


Err http://ftp.debian.org jessie-backports InRelease                            
                                                                                
Err http://http.debian.net jessie InRelease                                     
                                                                                
Err http://http.debian.net jessie-updates InRelease                             
                                                                                
Err http://http.debian.net jessie-backports InRelease                           
                                                                                
Err http://security.debian.org jessie/updates InRelease                         
                                                                                
Err http://repo.linaro.org jessie InRelease                                     
                                                                                
Err http://repo.linaro.org jessie InRelease                                     
                                                                                
Err http://http.debian.net jessie Release.gpg                                   
  Could not resolve 'http.debian.net'                                           
Err http://http.debian.net jessie-updates Release.gpg                           
  Could not resolve 'http.debian.net'                                           
Err http://security.debian.org jessie/updates Release.gpg                       
  Could not resolve 'security.debian.org'                                       
Err http://ftp.debian.org jessie InRelease                                      
                                                                                
Err http://repo.linaro.org jessie Release.gpg                                   
  Could not resolve 'repo.linaro.org'                                           
Err http://http.debian.net jessie-backports Release.gpg                         
  Could not resolve 'http.debian.net'                                           
Err http://repo.linaro.org jessie Release.gpg                                   
  Could not resolve 'repo.linaro.org'                                           
Err http://ftp.debian.org jessie-backports Release.gpg                          
  Could not resolve 'ftp.debian.org'                                            
Err http://ftp.debian.org jessie Release.gpg                                    
  Could not resolve 'ftp.debian.org'                                            
Reading package lists... Done                                                   
W: Failed to fetch http://http.debian.net/debian/dists/jessie/InRelease         
                                                                                
W: Failed to fetch http://security.debian.org/dists/jessie/updates/InRelease    
                                                                                
W: Failed to fetch http://http.debian.net/debian/dists/jessie-updates/InRelease 
                                                                                                                                                                
W: Failed to fetch http://http.debian.net/debian/dists/jessie-backports/InReleas
e                                                                               
                                                                                
W: Failed to fetch http://ftp.debian.org/debian/dists/jessie-backports/InRelease
                                                                                                                                                                
W: Failed to fetch http://ftp.debian.org/debian/dists/jessie/InRelease          
                                                                                
W: Failed to fetch http://repo.linaro.org/ubuntu/qcom-overlay/dists/jessie/InRel
ease                                                                            
                                                                                
W: Failed to fetch http://repo.linaro.org/ubuntu/linaro-overlay/dists/jessie/InR
elease                                                                          
                                                                                
W: Failed to fetch http://ftp.debian.org/debian/dists/jessie-backports/Release.g
pg  Could not resolve 'ftp.debian.org'                                          
                                                                                
W: Failed to fetch http://http.debian.net/debian/dists/jessie/Release.gpg  Could
 not resolve 'http.debian.net'                                                  
                                                                                
W: Failed to fetch http://http.debian.net/debian/dists/jessie-updates/Release.gp
g  Could not resolve 'http.debian.net'                                          
                                                                                
W: Failed to fetch http://http.debian.net/debian/dists/jessie-backports/Release.
gpg  Could not resolve 'http.debian.net'                                        
                                                                                
W: Failed to fetch http://security.debian.org/dists/jessie/updates/Release.gpg  
Could not resolve 'security.debian.org'                                         
                                                                                
W: Failed to fetch http://repo.linaro.org/ubuntu/qcom-overlay/dists/jessie/Relea
se.gpg  Could not resolve 'repo.linaro.org'                                     
                                                                                
W: Failed to fetch http://repo.linaro.org/ubuntu/linaro-overlay/dists/jessie/Rel
ease.gpg  Could not resolve 'repo.linaro.org'                                   
                                                                                
W: Failed to fetch http://ftp.debian.org/debian/dists/jessie/Release.gpg  Could 
not resolve 'ftp.debian.org'                                                    
                                                                                
W: Some index files failed to download. They have been ignored, or old ones used
 instead. 

But it can be updated on ALIP Desktop image.
Can anyone give me idea about this issue? thanks

My DNS servers are not set or not working properly.
I tried to set DNS servers to solve this problem:


#sudo vi /etc/resolv.conf
nameserver 8.8.8.8 //Google Server
#reboot

I have found in both Debian releases (15.11 and 16.02), I have had to edit /etc/NetworkManager/NetworkManager.conf and add the line “dns=dnsmasq” under [main] before the DNS would work properly.