network manager says "device not managed"
wired device not managed
Most probably your interface appears in /etc/network/interfaces. By default, NetworkManager does not manage interfaces that appear in /etc/network/interfaces. You can change this behaviour.
To do this - in a terminal:
sudo nano /etc/NetworkManager/NetworkManager.conf
change the line managed=false to managed=true
Save, stop and start network manager:
sudo service network-manager restart
Alternatively, you can remove the interface from /etc/network/interfaces.
backup the current interfaces file:
sudo cp /etc/network/interfaces /etc/network_interfaces_backup
Then open the file:
sudo nano /etc/network/interfaces
Delete everything in that file and copy and paste the following:
auto lo
iface lo inet loopback
Save, stop and start network manager:
sudo service network-manager restart
Double check in network manager (click on the indicator) that you have Enabled Networking ticked and you should also force deletion of old "wired connections" and selecting the new wired connection shown in the network manager indicator.
None of the given solutions worked for me. I was having this problem on an Ubuntu 16.04 machine I hadn't booted in a long time. After some more searching this command is what worked for me.
sudo touch /etc/NetworkManager/conf.d/10-globally-managed-devices.conf
wired device not managed
I had the same problem with a fresh install on my Asus Eee PC 1005HA. The live environment worked with no problems, but once installed I couldn't get the connection to respond or to not read "device not managed". When I changed the text in this configuration file and restarted Network Manager everything worked!
gksudo gedit /etc/NetworkManager/NetworkManager.conf
for lubuntu:
gksudo leafpad /etc/NetworkManager/NetworkManager.conf
Now the text editor will open. Find the line managed=false and replace false with true and save the file (ctrl+s) and close the file.
Restart your computer or the NetworkManager service (sudo service network-manager restart).