Creating users and roles in MongoDB - Practice Exercises

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this user creation command?

Consider the following MongoDB command to create a user with readWrite role on the 'sales' database:

db.createUser({
  user: "salesUser",
  pwd: "pass123",
  roles: [{ role: "readWrite", db: "sales" }]
})

What will be the result of running this command if the user does not exist yet?

MongoDB

db.createUser({ user: "salesUser", pwd: "pass123", roles: [{ role: "readWrite", db: "sales" }] })

A User 'salesUser' is created with readWrite access on 'sales' database and a success message is returned.

B SyntaxError: Missing parentheses in function call.

C AuthenticationFailed: Cannot create user without admin privileges.

D User 'salesUser' is created but has no roles assigned.

💡 Hint

Creating a user with roles requires specifying the role and database correctly.

The command creates a new user named 'salesUser' with password 'pass123' and assigns the readWrite role on the 'sales' database. MongoDB returns a success message if the user is created successfully.

📝 Syntax

intermediate

Which command correctly creates a role with read-only access on the 'inventory' database?

You want to create a custom role named 'inventoryRead' that allows reading any collection in the 'inventory' database. Which of the following commands is syntactically correct?

A db.createRole({ role: "inventoryRead", privileges: [{ resource: { db: "inventory", collection: "all" }, actions: ["find"] }], roles: [] })

B db.createRole({ role: "inventoryRead", privileges: [{ resource: { db: "inventory" }, actions: ["find"] }], roles: [] })

C db.createRole({ role: "inventoryRead", privileges: [{ resource: { db: "inventory", collection: "" }, actions: ["find"] }], roles: [] })

D db.createRole({ name: "inventoryRead", privileges: [{ resource: { db: "inventory", collection: "*" }, actions: ["read"] }], roles: [] })

💡 Hint

The 'collection' field should be an empty string to specify all collections.

Option C correctly uses 'role' as the field name, specifies the 'find' action for read access, and uses an empty string for 'collection' to mean all collections in the 'inventory' database.

❓ optimization

advanced

How to optimize role assignment for multiple databases?

You want to create a user who has readWrite access on both 'sales' and 'marketing' databases. Which command is the most efficient and correct way to assign these roles during user creation?

A db.createUser({ user: "multiDBUser", pwd: "pass456", roles: [{ role: "readWrite", db: "sales" }, { role: "readWrite", db: "marketing" }] })

B db.createUser({ user: "multiDBUser", pwd: "pass456", roles: [{ role: "readWrite", db: "sales,marketing" }] })

C db.createUser({ user: "multiDBUser", pwd: "pass456", roles: [{ role: "readWrite" }] })

D db.createUser({ user: "multiDBUser", pwd: "pass456", roles: ["readWrite"] })

💡 Hint

Each role must specify a single database.

Option A correctly assigns readWrite role separately for each database. Option A is invalid because 'db' cannot list multiple databases as a string. Options C and D lack database specification or proper role structure.

🔧 Debug

advanced

Why does this role creation command fail?

You run this command to create a role:

db.createRole({
  role: "dataAnalyst",
  privileges: [{ resource: { db: "analytics", collection: "reports" }, actions: ["find", "update"] }],
  roles: [{ role: "read", db: "analytics" }]
})

But it fails with an error. What is the most likely cause?

A The 'actions' array contains 'update' which is not a valid action.

B The 'roles' array references a role 'read' which is invalid; it should be 'readAnyDatabase' or 'readWrite'.

C The role 'read' does not exist; it should be 'readAnyDatabase'.

D The 'roles' array should be empty when privileges are specified.

💡 Hint

Check the validity of roles referenced inside the roles array.

The built-in role is 'read' only at the database level, but when specifying roles inside createRole, the role name must be exact and valid. 'read' is valid only if it exists on the specified database. If it does not, the command fails. Usually, 'read' is valid, but if the database or role is misspelled or missing, it causes failure. Here, the error is caused by referencing a role that does not exist or is misspelled.

🧠 Conceptual

expert

What is the effect of assigning the 'root' role to a user?

In MongoDB, if you create a user and assign the built-in 'root' role, what does this role allow the user to do?

A The user has read-only access to all databases.

B The user can only read and write data on the admin database.

C The user can only create and delete collections but cannot manage users.

D The user can perform any action on any database, including user and role management.

💡 Hint

Think about the highest level of access in MongoDB.

The 'root' role is the highest built-in role in MongoDB. It grants full administrative privileges across all databases, including the ability to manage users, roles, and perform any database operation.

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