Error creating default "bridge" network: cannot create network (docker0): conflicts with network (docker0): networks have same bridge name

For me I downgraded my OS (Centos Atomic Host in this case) and came across this error message. The docker of the older Centos Atomic was 1.9.1. I did not have any running docker containers or images pulled before running the downgrade.

I simply ran the below and docker was happy again:

sudo rm -rf /var/lib/docker/network
sudo systemctl start docker

More info.

The Problem seems to be in /var/docker/network/. There are a lot of sockets stored that reference the bridge by its old id. To solve the Problem you can delete all sockets, delete the interface and then start docker but all your container will refuse to work since their sockets are gone. In my case I did not care about my stateless containers anyway so this fixed the problem:

ip link del docker0
rm -rf /var/docker/network/*
mkdir /var/docker/network/files
systemctl start docker
# delete all containers
docker ps -a | cut -d' ' -f 1 | xargs -n 1 echo docker rm  -f
# recreate all containers