Use of parameter USER en ETCD

Hello, I have a query, when I do a ETCD Backup I usually do it like this:

export EDTCD_API=3** ** ETCDCTL=3 etcdctl snapshot save /tmp/etcd-backup.db --cacert=/etc/kubernetes/pki/etcd/ca.crt --cert=/etc/kubernetes/pki/etcd/server.crt --key=/etc/kubernetes/pki/etcd/server.key

But I have seen that the parameter is also used: –user=. My question is that if its use is necessarily necessary and if I require it, what part of the file: etcd.yaml should I get it?

Thank you.