etcd upgrade

etcd 2.3升级到3.0， v2数据转v3

主：

systemctl stop etcd
etcdctl backup --data-dir=/home/data --backup-dir=/home/etcd20181217

恢复:
1、复制数据，启动etcd

cp -r etcd20181217 /var/lib/etcd
etcd --data-dir=/var/lib/etcd --force-new-cluster

2、v2转v3

pkill etcd
export ETCDCTL_API=3
etcdctl migrate --data-dir /var/lib/etcd
systemctl start etcd
etcdctl get / --prefix --keys-only

已经显示数据