#### 18.2.1.4 Launching Group Replication

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 Once server s1 has been configured and started, install the Group Replication plugin. If you used `plugin_load_add='group_replication.so'` in the option file then the Group Replication plugin is installed and you can proceed to the next step. In the event that you decide to install the plugin manually, connect to the server and issue the following:

```
INSTALL PLUGIN group_replication SONAME 'group_replication.so';
```

Important

 The `mysql.session` user must exist before you can load Group Replication. `mysql.session` was added in MySQL version 8.0.2. If your data dictionary was initialized using an earlier version you must perform the MySQL upgrade procedure (see [Section 2.11, “Upgrading MySQL”](upgrading.html)). If the upgrade is not run, Group Replication fails to start with the error message There was an error when trying to access the server with user: mysql.session@localhost. Make sure the user is present in the server and that mysql\_upgrade was ran after a server update..

 To check that the plugin was installed successfully, issue `SHOW PLUGINS;` and check the output. It should show something like this:

```
mysql> SHOW PLUGINS;
+----------------------------+----------+--------------------+----------------------+-------------+
| Name                       | Status   | Type               | Library              | License     |
+----------------------------+----------+--------------------+----------------------+-------------+
| binlog                     | ACTIVE   | STORAGE ENGINE     | NULL                 | PROPRIETARY |

(...)

| group_replication          | ACTIVE   | GROUP REPLICATION  | group_replication.so | PROPRIETARY |
+----------------------------+----------+--------------------+----------------------+-------------+
```

