If you tried to add node to your etcd cluster and it failed, your cluster may have lost quorum and will not start again. To recover it you need to create new cluster identity. This is a short howto.

1. Backup current cluster

   etcdctl backup --data-dir /var/lib/etcd/ --backup-dir etcd-backup

2. Stop etcd service

   service etcd_container stop

3. Get a command used for starting etcd

   cat /etc/systemd/system/etcd_container.service

4. Run the same command with adding parameter –force-new-cluster

   /usr/bin/docker run --name etcd_container --rm -v /var/lib/etcd:/var/lib/etcd:z -v /etc/etcd:/etc/etcd:ro --env-file=/etc /etcd/etcd.conf --net=host --entrypoint=/usr/bin/etcd registry.access.redhat.com/rhel7/etcd --force-new-cluster

5. Wait until it correctly starts and stop it with Ctrl+C
6. Start etcd again

    service etcd_container stop