Creating users and roles in MongoDB

Introduction

Creating users and roles helps control who can access your database and what they can do. It keeps your data safe and organized.

When you want to give someone permission to read data but not change it.

When you need to allow a user to add or update data in the database.

When you want to create a special role for a group of users with specific permissions.

When you want to restrict access to certain parts of your database.

When setting up a new database and need to secure it from unauthorized access.

Syntax

MongoDB

db.createUser({
  user: "username",
  pwd: "password",
  roles: [
    { role: "roleName", db: "databaseName" }
  ]
})

// To create a role:
db.createRole({
  role: "roleName",
  privileges: [
    {
      resource: { db: "databaseName", collection: "collectionName" },
      actions: ["action1", "action2"]
    }
  ],
  roles: []
})

Use db.createUser() to add a new user with specific roles.

Use db.createRole() to define a custom role with specific privileges.

Examples

Creates a user who can only read data from 'myDatabase'.

MongoDB

db.createUser({
  user: "readerUser",
  pwd: "readerPass",
  roles: [ { role: "read", db: "myDatabase" } ]
})

Creates a user with administrative rights on 'myDatabase'.

MongoDB

db.createUser({
  user: "adminUser",
  pwd: "adminPass",
  roles: [ { role: "dbAdmin", db: "myDatabase" } ]
})

Creates a custom role that allows reading and writing on 'myCollection' in 'myDatabase'.

MongoDB

db.createRole({
  role: "customReadWrite",
  privileges: [
    {
      resource: { db: "myDatabase", collection: "myCollection" },
      actions: ["find", "insert", "update"]
    }
  ],
  roles: []
})

Sample Program

This creates a role 'limitedEditor' that can read and update the 'products' collection. Then it creates a user 'editorUser' with that role.

MongoDB

use myDatabase

db.createRole({
  role: "limitedEditor",
  privileges: [
    {
      resource: { db: "myDatabase", collection: "products" },
      actions: ["find", "update"]
    }
  ],
  roles: []
})

db.createUser({
  user: "editorUser",
  pwd: "editorPass",
  roles: [ { role: "limitedEditor", db: "myDatabase" } ]
})

Important Notes

Always use strong passwords for users to keep your database secure.

Roles can include other roles to combine permissions easily.

You must have admin rights to create users and roles.

Summary

Creating users controls who can access your database.

Roles define what actions users can perform.

You can create custom roles for specific permissions.

Practice

1. What is the primary purpose of creating users in MongoDB?

easy

A. To control who can access the database

B. To store data in collections

C. To optimize query performance

D. To backup the database automatically

Solution

1. Step 1: Understand user creation in MongoDB

   Users in MongoDB are created to manage access to the database system.

2. Step 2: Identify the purpose of users

   Users control who can connect and perform actions on the database.

3. Final Answer:

   To control who can access the database -> Option A

4. Quick Check:

   Users = Access control [OK]

Hint: Users manage access, not data or backups [OK]

Common Mistakes:

• Confusing users with data storage
• Thinking users optimize queries
• Assuming users handle backups

2. Which of the following is the correct syntax to create a user with read-only access on the sales database in MongoDB?

easy

A. db.createUser({user: 'reader', pwd: 'pass', roles: [{role: 'read', db: 'sales'}]})

B. db.createUser({user: 'reader', pwd: 'pass', roles: ['read']})

C. db.addUser('reader', 'pass', 'read')

D. db.users.insert({user: 'reader', pwd: 'pass', role: 'read'})

Solution

1. Step 1: Recall MongoDB user creation syntax

   The correct syntax uses db.createUser() with roles as an array of objects specifying role and database.

2. Step 2: Check each option

   db.createUser({user: 'reader', pwd: 'pass', roles: [{role: 'read', db: 'sales'}]}) correctly specifies the role 'read' on the 'sales' database. db.createUser({user: 'reader', pwd: 'pass', roles: ['read']}) misses the database name, C uses deprecated syntax, D tries to insert directly into users collection which is invalid.

3. Final Answer:

   db.createUser({user: 'reader', pwd: 'pass', roles: [{role: 'read', db: 'sales'}]}) -> Option A

4. Quick Check:

   Roles need role and db fields [OK]

Hint: Roles need role and db fields in array [OK]

Common Mistakes:

• Omitting the database in roles
• Using deprecated addUser method
• Trying to insert user directly into collection

3. Given the following command in MongoDB shell:

db.createUser({user: 'adminUser', pwd: 'secure123', roles: [{role: 'userAdminAnyDatabase', db: 'admin'}]})

What permission does the user adminUser have?

medium

A. Can read data from any database

B. Can manage users on any database

C. Can only read the admin database

D. Can write data to any database

Solution

1. Step 1: Understand the role userAdminAnyDatabase

   This role allows managing users and roles across all databases.

2. Step 2: Analyze the permissions given

   The user can create, modify, and delete users on any database but does not have read or write data permissions by default.

3. Final Answer:

   Can manage users on any database -> Option B

4. Quick Check:

   userAdminAnyDatabase = user management [OK]

Hint: userAdminAnyDatabase manages users, not data [OK]

Common Mistakes:

• Assuming it grants read or write data access
• Confusing admin database with all databases
• Thinking it only applies to admin database

4. You try to create a user with this command:

db.createUser({user: 'testUser', pwd: 'test123', roles: ['readWrite']})

But it fails. What is the most likely reason?

medium

A. Password is too short

B. User already exists

C. Roles must be objects specifying role and database

D. Missing database name in createUser command

Solution

1. Step 1: Check roles format in createUser

   Roles must be an array of objects with role and db fields, not just strings.

2. Step 2: Identify the error cause

   The command uses roles as strings, which is invalid syntax causing failure.

3. Final Answer:

   Roles must be objects specifying role and database -> Option C

4. Quick Check:

   Roles = [{role: '', db: ''}] [OK]

Hint: Roles need role and db objects, not strings [OK]

Common Mistakes:

• Using role names as plain strings
• Ignoring role database specification
• Assuming password length causes failure

5. You want to create a custom role named reportViewer that allows users to only read data from the reports collection in the analytics database. Which command correctly creates this role?

hard

A. db.createRole({role: 'reportViewer', privileges: [{resource: {db: 'analytics', collection: 'reports'}, actions: ['read']}], roles: []})

B. db.createRole({role: 'reportViewer', privileges: [{resource: {db: 'analytics'}, actions: ['read']}], roles: []})

C. db.createRole({role: 'reportViewer', privileges: [{resource: {collection: 'reports'}, actions: ['find']}], roles: []})

D. db.createRole({role: 'reportViewer', privileges: [{resource: {db: 'analytics', collection: 'reports'}, actions: ['find']}], roles: []})

Solution

1. Step 1: Understand custom role creation syntax

   Custom roles require specifying privileges with resource (db and collection) and actions allowed.

2. Step 2: Analyze each option's privileges

   db.createRole({role: 'reportViewer', privileges: [{resource: {db: 'analytics', collection: 'reports'}, actions: ['find']}], roles: []}) correctly specifies the database 'analytics', collection 'reports', and action 'find' which allows reading documents. db.createRole({role: 'reportViewer', privileges: [{resource: {db: 'analytics'}, actions: ['read']}], roles: []}) uses 'read' action on the whole database, not just the collection. db.createRole({role: 'reportViewer', privileges: [{resource: {collection: 'reports'}, actions: ['find']}], roles: []}) misses the database name. db.createRole({role: 'reportViewer', privileges: [{resource: {db: 'analytics', collection: 'reports'}, actions: ['read']}], roles: []}) uses 'read' action which is not a valid action for privileges; 'find' is correct for reading documents.

3. Final Answer:

   db.createRole({role: 'reportViewer', privileges: [{resource: {db: 'analytics', collection: 'reports'}, actions: ['find']}], roles: []}) -> Option D

4. Quick Check:

   Custom role needs db, collection, and 'find' action [OK]

Hint: Use 'find' action for read on specific collection [OK]

Common Mistakes:

• Using 'read' action instead of 'find'
• Omitting database name in resource
• Specifying collection without database