Merge pull request #8075 from gyuho/upgrade-doc

Documentation/upgrades: link to previous guides

Documentation/upgrades/upgrade_3_0.md

@@ -10,7 +10,7 @@ Before [starting an upgrade](#upgrade-procedure), read through the rest of this
 
 #### Upgrade requirements
 
-To upgrade an existing etcd deployment to 3.0, the running cluster must be 2.3 or greater. If it's before 2.3, please upgrade to [2.3](https://github.com/coreos/etcd/releases/tag/v2.3.0) before upgrading to 3.0.
+To upgrade an existing etcd deployment to 3.0, the running cluster must be 2.3 or greater. If it's before 2.3, please upgrade to [2.3](https://github.com/coreos/etcd/releases/tag/v2.3.8) before upgrading to 3.0.
 
 Also, to ensure a smooth rolling upgrade, the running cluster must be healthy. Check the health of the cluster by using the `etcdctl cluster-health` command before proceeding.
 
@@ -52,7 +52,7 @@ member 8211f1d0f64f3269 is healthy: got healthy result from http://localhost:123
 cluster is healthy
 
 $ curl http://localhost:2379/version
-{"etcdserver":"2.3.x","etcdcluster":"2.3.0"}
+{"etcdserver":"2.3.x","etcdcluster":"2.3.8"}
 ```
 
 #### 2. Stop the existing etcd process

Documentation/upgrades/upgrade_3_1.md

@@ -10,7 +10,7 @@ Before [starting an upgrade](#upgrade-procedure), read through the rest of this
 
 #### Upgrade requirements
 
-To upgrade an existing etcd deployment to 3.1, the running cluster must be 3.0 or greater. If it's before 3.0, please upgrade to [3.0](https://github.com/coreos/etcd/releases/tag/v3.0.16) before upgrading to 3.1.
+To upgrade an existing etcd deployment to 3.1, the running cluster must be 3.0 or greater. If it's before 3.0, please [upgrade to 3.0](upgrade_3_0.md) before upgrading to 3.1.
 
 Also, to ensure a smooth rolling upgrade, the running cluster must be healthy. Check the health of the cluster by using the `etcdctl endpoint health` command before proceeding.
 

Documentation/upgrades/upgrade_3_2.md

@@ -50,7 +50,7 @@ clientv3yaml.NewConfig
 
 #### Upgrade requirements
 
-To upgrade an existing etcd deployment to 3.2, the running cluster must be 3.1 or greater. If it's before 3.1, please upgrade to [3.1](https://github.com/coreos/etcd/releases/tag/v3.1.7) before upgrading to 3.2.
+To upgrade an existing etcd deployment to 3.2, the running cluster must be 3.1 or greater. If it's before 3.1, please [upgrade to 3.1](upgrade_3_1.md) before upgrading to 3.2.
 
 Also, to ensure a smooth rolling upgrade, the running cluster must be healthy. Check the health of the cluster by using the `etcdctl endpoint health` command before proceeding.