failed to start daemon: Error initializing network controller: Error creating default "bridge" network
Found out that
$ firewall-cmd --get-active-zones FedoraWorkstation interfaces: ens4u1u2 wlp59s0 docker interfaces: br-48d7d996793a libvirt interfaces: virbr0 trusted interfaces: docker0
the interface docker0 seems to be in the trusted zone. But there's another zone called docker.
So I decided to give it a shot and add it to the docker zone instead.
$ sudo firewall-cmd --zone=docker --change-interface=docker0
Looks like this afterwards:
$ firewall-cmd --get-active-zones FedoraWorkstation interfaces: ens4u1u2 wlp59s0 docker interfaces: br-48d7d996793a docker0 libvirt interfaces: virbr0
Seems to work.
Maybe someone can shed more light on this.
I got this error after upgrading docker-ce on my Fedora 32. It looks like the new docker conflicts with the manual firewall configuration mentioned in the article you linked in your answer. I had the rules on my machine to enable container-to-container communication.
Docker started successfully after I reverted the firewall rules:
sudo firewall-cmd --permanent --zone=trusted --remove-interface=docker0 sudo firewall-cmd --permanent --zone=FedoraWorkstation --remove-masquerade sudo firewall-cmd --reload sudo systemctl restart docker
The changes don't seem to affect the ability of containers to talk to each other.