如何创建一个角色

建立一个用户角色使用createRole这个命令。每一个角色可以通过privileges授予一些系统特权，通过roles来授予一些数据库管理权限。writeConcern参数是保障写操作的可靠性。

use admin

db.createRole(
  {
    role: "myClusterwideAdmin",
    privileges:
    [
      { resource: { cluster: true }, actions: [ "addShard" ] },
      { resource: { db: "config", collection: "" }, actions: [ "find", "update", "insert" ] },
      { resource: { db: "users", collection: "usersCollection" }, actions: [ "update" ] },
      { resource: { db: "", collection: "" }, actions: [ "find" ] }
    ],
    roles:
    [
      { role: "read", db: "admin" }
    ],
    writeConcern: { w: "majority" , wtimeout: 5000 }
  }
)
)