在安裝好flanneld之后。修改docker配置，重啟docker的過程中報錯：

journalctl -x -u docker

Jan 24 11:54:53 myserver dockerd[11139]: time="2019-01-24T11:54:53.565543199+08:00" level=info msg="stopping event stream following graceful sh
Jan 24 11:54:53 myserver dockerd[11139]: time="2019-01-24T11:54:53.565710638+08:00" level=info msg="stopping healthcheck following graceful shu
Jan 24 11:54:53 myserver dockerd[11139]: time="2019-01-24T11:54:53.565726454+08:00" level=info msg="stopping event stream following graceful sh
Jan 24 11:54:53 myserver dockerd[11139]: time="2019-01-24T11:54:53.566335880+08:00" level=info msg="pickfirstBalancer: HandleSubConnStateChange
Jan 24 11:54:53 myserver dockerd[11139]: time="2019-01-24T11:54:53.566356643+08:00" level=info msg="pickfirstBalancer: HandleSubConnStateChange
Jan 24 11:54:54 myserver dockerd[11139]: Error starting daemon: Error initializing network controller: Error creating default "bridge" network:
Jan 24 11:54:54 myserver systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
Jan 24 11:54:54 myserver systemd[1]: Failed to start Docker Application Container Engine.
-- Subject: Unit docker.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit docker.service has failed.
--
-- The result is failed.
Jan 24 11:54:54 myserver systemd[1]: Unit docker.service entered failed state.
Jan 24 11:54:54 myserver systemd[1]: docker.service failed.
Jan 24 11:54:54 myserver systemd[1]: docker.service holdoff time over, scheduling restart.
Jan 24 11:54:54 myserver systemd[1]: start request repeated too quickly for docker.service
Jan 24 11:54:54 myserver systemd[1]: Failed to start Docker Application Container Engine.
-- Subject: Unit docker.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit docker.service has failed.
--
-- The result is failed.

關鍵信息：
Jan 24 11:54:54 myserver dockerd[11139]: Error starting daemon: Error initializing network controller: Error creating default “bridge” network:

解決方法

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