Essential MongoDB Commands for Developers

MongoDB is a powerful NoSQL database, but managing users, authentication, and backups can sometimes be tricky. This article is a ,y quick cheat sheet for developers, providing essential MongoDB commands tested on a self-managed MongoDB instance running on localhost.

---

First things first – connecting to MongoDB

Logging into MongoDB from the terminal:

mongo -u 'username' -p 'your-secure-password' --authenticationDatabase admin

If your database user is tied to a specific database (e.g., custom_db), use:

mongo -u admin -p 'your-secure-password' --authenticationDatabase custom_db

---

Creating a New User

To create a user with full permissions on a specific database:

use ams;
db.createUser({
  user: "user_dev",
  pwd: "your-secure-password",
  roles: [{ role: "dbOwner", db: "my_db_instance_name" }]
});

If you need a read-only user:

db.createUser({
  user: "user_readonly",
  pwd: "readonly-password",
  roles: [{ role: "read", db: "my_db_instance_name" }]
});

---

Changing a User’s Password

For security, changing passwords periodically is a good practice. Here’s how to update a user’s password:

use admin;
db.changeUserPassword("admin", "new-secure-password");

For a user in another database:

use different_db;
db.changeUserPassword("user_dev", "new-secure-password");

---

Listing Users in a Database

To see all users in the my_db_instance_name database:

use my_db_instance_name;
db.getUsers();

---

Backing Up a MongoDB Database

To create a compressed backup of your database:

mongodump --host mongodb --port 27017 -u "$DB_USER" -p "$DB_PWD" \
  --authenticationDatabase "my_db_instance_name" --db "my_db_instance_name" --archive=backup-$(date +%F).gz --gzip

This command dumps the my_db_instance_name database into a .gz file with a timestamp.

---

Restoring a MongoDB Backup

Restoring a backup is just as easy:

mongorestore --host mongodb --port 27017 -u "$DB_USER" -p "$DB_PWD" \
  --authenticationDatabase "my_db_instance_name" --db "my_db_instance_name" --gzip --archive=backup-YYYY-MM-DD.gz

Make sure to replace YYYY-MM-DD with the correct backup file date.

---

Running MongoDB in Docker

If you’re using Docker, running MongoDB with authentication enabled requires the --auth flag. Below is an example of how to run MongoDB in a Docker container with authentication, persistent storage, and proper environment variables:

version: '3.8'
services:
  mongodb:
    image: mongo:latest
    restart: always
    environment:
      MONGO_INITDB_ROOT_USERNAME: admin
      MONGO_INITDB_ROOT_PASSWORD: your-secure-password
    volumes:
      - mongo-data:/data/db
    command: ["mongod", "--auth"]
    ports:
      - "27017:27017"
volumes:
  mongo-data:

This setup ensures that MongoDB retains data even if the container is restarted or removed. Start MongoDB with docker compose:

docker-compose up -d

You can then connect to it using:

mongo -u admin -p 'your-secure-password' --authenticationDatabase admin

---

Additional Useful MongoDB Commands

Listing All Databases

To see all available databases:

show dbs

Listing All Collections in a Database

To check available collections:

use my_db_instance_name;
show collections

Checking Storage Statistics for a Collection

To analyze how much space a collection is using:

db.my_collection.stats()

---