内建角色，具体参考：https://docs.mongodb.com/manual/reference/built-in-roles

Read：允许用户读取指定数据库
readWrite：允许用户读写指定数据库
dbAdmin：允许用户在指定数据库中执行管理函数，如索引创建、删除，查看统计或访问system.profile
userAdmin：允许用户向system.users集合写入，可以找指定数据库里创建、删除和管理用户
clusterAdmin：只在admin数据库中可用，赋予用户所有分片和复制集相关函数的管理权限。
readAnyDatabase：只在admin数据库中可用，赋予用户所有数据库的读权限
readWriteAnyDatabase：只在admin数据库中可用，赋予用户所有数据库的读写权限
userAdminAnyDatabase：只在admin数据库中可用，赋予用户所有数据库的userAdmin权限
dbAdminAnyDatabase：只在admin数据库中可用，赋予用户所有数据库的dbAdmin权限。
root：只在admin数据库中可用。超级账号，超级权限

用户文件在admin库下的system.users表里，默认MongoDB没有访问密码，不太安全

1.添加数据库管理员用户adminUser和普通用户herrywen

mongo --port 27017
use admin
db.createUser(
{
user: "adminUser",
pwd: "adminPass",
roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]
}
)

use herrywen
db.createUser(
  {
    user: "herrywen",
    pwd: "herrywen",
    roles: [ { role: "readWrite", db: "herrywen" },
             { role: "read", db: "admin" } ]
  }
)

2.在192.168.255.134增加配置文件，开启验证

cat /etc/mongod.conf
security:
  authorization: enabled

3.重启mongdb服务
systemctl restart mongdb

4.测试看下是否可以访问了

[root@worker1 ~]# mongo --host 192.168.255.134 --port 27017  -u adminUser -p adminPass --authenticationDatabase "admin"
MongoDB shell version v4.2.1
connecting to: mongodb://192.168.255.134:27017/?authSource=admin&compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("f5114890-0b2e-43a2-8a60-a8b265e68a44") }
MongoDB server version: 4.2.1
MongoDB Enterprise > use admin;
switched to db admin
MongoDB Enterprise > show collections;
system.users
system.version
MongoDB Enterprise > exit
bye

5.如果直接登陆，在切换admin库时，提示没有任何权限。需要使用db.auth()进行验证

[root@worker1 ~]# mongo --host 192.168.255.134 --port 27017
MongoDB shell version v4.2.1
connecting to: mongodb://192.168.255.134:27017/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("9bcb1b37-7cfa-4aff-8947-6d633eee01be") }
MongoDB server version: 4.2.1
MongoDB Enterprise > use admin
switched to db admin
MongoDB Enterprise > show collections;
Warning: unable to run listCollections, attempting to approximate collection names by parsing connectionStatus
MongoDB Enterprise > show collections;
Warning: unable to run listCollections, attempting to approximate collection names by parsing connectionStatus
MongoDB Enterprise > db.auth("adminUser","adminPass")
1
MongoDB Enterprise > show collections;
system.users
system.version

6.直接登陆herrywen库

[root@worker1 ~]# mongo --host 192.168.255.134 --port 27017  -u herrywen -p herrywen --authenticationDatabase "herrywen"
MongoDB shell version v4.2.1
connecting to: mongodb://192.168.255.134:27017/?authSource=herrywen&compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("9d906997-681a-43b4-b541-dbe5d197cd1f") }
MongoDB server version: 4.2.1
MongoDB Enterprise > use herrywen
switched to db herrywen
MongoDB Enterprise > show collections;
MongoDB Enterprise > db.test3.insert({title: 'MongoDB',
...     description: 'hello,world',
...     by: 'herrywen',
...     url: 'http://www.51cto.com',
...     tags: ['mongodb', 'database', 'NoSQL'],
...     likes: 100})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise > show collections;

7.给adminUser用户增加对herrywen库的读写权限

use admin
db.grantRolesToUser(     "adminUser",     [       { role: "readWrite", db: "herrywen" }     ] )
db.system.users.find().pretty();  

8.给herrywen用户增加herrywen1库的读写权限和admin数据库的读权限

use herrywen
db.grantRolesToUser(     "herrywen",     [       { role: "readWrite", db: "herrywen1" } ,{ role: "read", db: "admin" }   ] )

9.撤销herrywen对herrywen1库的读写权限和admin数据库的读权限

db.revokeRolesFromUser(
    "herrywen",
    [
                {
                        "role" : "read",
                        "db" : "admin"
                },
                {
                        "role" : "readWrite",
                        "db" : "herrywen1"
                }
     ]
)

10.查看当前herrywen用户的权限，也可以切换heryrwen数据库下，使用db.getUser('herrywen')查看，但是比较麻烦,可以直接使用show users

MongoDB Enterprise > show users
{
        "_id" : "herrywen.herrywen",
        "userId" : UUID("68fc696d-9825-43b6-9afb-d4a040b480a3"),
        "user" : "herrywen",
        "db" : "herrywen",
        "roles" : [
                {
                        "role" : "readWrite",
                        "db" : "herrywen"
                }
        ],
        "mechanisms" : [
                "SCRAM-SHA-1",
                "SCRAM-SHA-256"
        ]
}

11.修改herrywen用户的密码
db.changeUserPassword("herrywen","herrywen-2")

12.删除herrywen用户
db.dropUser("herrywen")