Here’s how you solve either of the following errors on Ubuntu (and possibly Debian):
device br0 already exists; can't create bridge with the same name device eth0 is already a member of a bridge; can't enslave it to bridge br1.
Removing the device specs from /etc/network/interfaces and restarting the network doesn’t actually remove the device if already active. You need to do it manually.
List the active devices:
ifconfig | more
And then do this to any that you don’t want there, such as br0, eth0, eth1, etc:
ifconfig br0 down # and so on
This deactivates the device. At this point you’ll need to restart the network layer twice:
sudo /etc/init.d/networking restart sudo /etc/init.d/networking restart
And you should be sitting pretty. On some systems, networking is known as network, as in:
sudo /etc/init.d/network restart sudo /etc/init.d/network restart