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system.users Collection

The system.users collection in the admin database stores user authentication and authorization information. To manage data in this collection, MongoDB provides user management commands.

system.users Schema

The documents in the system.users collection have the following schema:

{
  _id: <system defined id>,
  userId : <system assigned UUID>,  // Starting in MongoDB 4.0.9
  user: "<name>",
  db: "<database>",
  credentials: { <authentication credentials> },
  roles: [
           { role: "<role name>", db: "<database>" },
           ...
         ],
  customData: <custom information>,
  authenticationRestrictions : [ <documents> ] // Starting in MongoDB 4.0
 }

Each system.users document has the following fields:

admin.system.users.userId

A unique identifier for the user assigned to the user upon creation.

userId is available for users created in MongoDB 4.0.9 and later.

New in version 4.0.9.

admin.system.users.user

The user name. A user exists in the context of a single logical database (see admin.system.users.db) but can have access on other databases through roles specified in the roles array.

admin.system.users.db

The authentication database associated with the user. The user’s privileges are not necessarily limited to this database. The user can have privileges in additional databases through the roles array.

admin.system.users.credentials

User’s authentication information. For users with externally stored authentication credentials, such as users that use Kerberos or x.509 certificates for authentication, the system.users document for that user does not contain the credentials field. For SCRAM user credentials, the information includes the mechanism, iteration count, and authentication parameters.

admin.system.users.roles

An array of roles granted to the user. The array contains both built-in roles and user-defined role.

A role document has the following syntax:

{ role: "<role name>", db: "<database>" }

A role document has the following fields:

admin.system.users.roles[n].role

The name of a role. A role can be a built-in role provided by MongoDB or a custom user-defined role.

admin.system.users.roles[n].db

The name of the database where role is defined.

When specifying a role using the role management or user management commands, you can specify the role name alone (e.g. "readWrite") if the role that exists on the database on which the command is run.

admin.system.users.customData

Optional custom information about the user.

admin.system.users.authenticationRestrictions

An array of authentication restrictions the server enforces for the user. The array containsa list of IP addresses and CIDR ranges from which the user is allowed to connect to the server or from which the server can accept users.

New in version 4.0.

Example

Consider the following document in the system.users collection:

{
   "_id" : "home.Kari",
   "userId" : UUID("ec1eced7-055a-4ca8-8737-60dd02c52793"),  // Available starting in MongoDB 4.0.9
   "user" : "Kari",
   "db" : "home",
   "credentials" : {
      "SCRAM-SHA-1" : {
         "iterationCount" : 10000,
         "salt" : "S/xM2yXFosynbCu4GzFDgQ==",
         "storedKey" : "Ist4cgpEd1vTbnRnQLdobgmOsBA=",
         "serverKey" : "e/0DyzS6GPboAA2YNBkGYm87+cg="
      },
      "SCRAM-SHA-256" : {
         "iterationCount" : 15000,
         "salt" : "p1G+fZadAeYAbECN8F/6TMzXGYWBaZ3DtWM0ig==",
         "storedKey" : "LEgLOqZQmkGhd0owm/+6V7VdJUYJcXBhPUvi9z+GBfk=",
         "serverKey" : "JKfnkVv9iXwxyc8JaapKVwLPy6SfnmB8gMb1Pr15T+s="
      }
   },
   "authenticationRestrictions" : [                           // Available starting in MongoDB 4.0
      { "clientSource" : [ "69.89.31.226" ], "serverAddress" : [ "172.16.254.1" ] }
   ],
   "customData" : {
      "zipCode" : "64157"
   },
   "roles" : [
      {
         "role" : "read",
         "db" : "home"
      },
      {
         "role" : "readWrite",
         "db" : "test"
      }
   ]
}

The document shows that a user Kari’s authentication database is the home database. Kari has the read role in the home database, the readWrite role in the test database.