I installed MongoDB on my local computer as a service. I can open Compass and access databases from there. But I have a couple of question that are really confusing for me:

1. Why is there mongod command? What does it do? I found it in documentation and it says

mongod is the primary daemon process for the MongoDB system. It handles data requests, manages data access, and performs background management operations.

But it is confusing, because I accessed server via Compass, without running mongod. I can even create databases and collections from there. Then what is the purpose of mongod?

2. Why does mongod demand C:\data\db folder? There is already a data folder in C:\Program Files\MongoDB\Server\5.0\data.

What is the difference between these two folders?

Again, in the official docs it says that it is needed for storing data.

But, I think I was in C:\Program Files\MongoDB\Server\5.0\data when I accessed database via Compass without mongod (because obviously the first one does not exist yet). Why would I create C:\data\db?

CodePudding user response：

1) Why is there mongod command? What does it do?

When we run mongod we are essentialy starting up a new database.

Since we should not interact with the mongod process directly we use a database client that is programmed to communicate with mongod.

Here, when we issue database commands like create or update this client takes care of communicating with mongod to execute these commands.

That's why we are using MongoDB Clients. If mongod process is not up and running this clients cannot communicate with mongod.

Thats why we are issuing sudo systemctl start mongod

Examples of MongoDB Clients:

• mogosh
• MongoDB Compass (GUI)
• Drivers (Node.js, Java, C/C )

2) On Windows, the dbpath is on the drive from which you start mongod process.

So looks like you started mongod process from the drive C:\Program Files\MongoDB\Server\5.0\data or you passed --dbpath flag

Otherwise it would have been C:\data\db

CodePudding user response：

But it is confusing, because I accessed server via Compass, without running mongod.

No, you cannot! MongoDB is installed as service which runs mongod automatically at boot time.

Folder \data\db (on the current drive) is the default folder used when no dbPath is provided - neither in configuration file nor as command line parameter.

Looks like sometimes you start mongod directly without any parameters, then above default applies. And sometimes mongod is started as service where storage.dbPath: C:\Program Files\MongoDB\Server\5.0\data is configured.

See also What is the default database path for MongoDB?

Update

My preferred way for Windows installation is this one:

1. Run the .msi installer or unzip the .zip file. Uncheck "Install MongoD as a Service" option

2. Create your personal mongod.cfg file according to your preferences (see sample below)

3. Install MongoDB as service by running

   mongod.exe --config <your mongod.cfg file> --install
   

Note, dbPath folder needs to be created manually before you start the service. Ensure user of mongod process has write permissions to it.

Sample mongod.cfg file:

# Where and how to store data.
storage:
  dbPath: C:\MongoDB\data\mongod

# where to write logging data.
systemLog:
  destination: file
  logAppend: true
  path:  C:\MongoDB\log\mongod.log

# network interfaces
net:
  port: 27017
  bindIp: localhost

processManagement:
  windowsService:
    serviceName: MongoDB
    displayName: MongoDB
    description: MongoDB Server

security:
  authorization: enabled

See mongoDB-oneClick