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Creating a MongoDB Instance

Creation of a MongoDB instance.

MongoDB instances are created through the dmk_db_create.py script. All commands are executed as the mongodb user.

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Using DMK templates

Instances are created using templates, which you can copy and modify from the $DMK_HOME/templates/dbcreate directory.

Let's go through an example with the template dbcreate_template_basic.yaml.

dbcreate_template_basic.yaml
mongo_cfg:
   instance_name: mdb01
   home_path: /u01/app/mongodb/product/8.0.16
   data_path: ${MONGO_DATA}
   bindIp: 0.0.0.0
   port: 27017
   template: ${DMK_HOME}/templates/dbcreate/mongo_conf_basic.yaml

This DMK template contains the following arguments :

  • instance_name: Name of the instance, which must comply with the INSTANCE_NAMING_CONVENTION defined in the DMK configuration file. By default, it is set to ^mdb([a-zA-Z]{0,4})(\d+)$, but you can customize it in your local configuration file.

  • home_path: Path to the MongoDB binaries associated with the instance. This path is stored in the $DMK_HOME/etc/mongodb.lst file and used when loading the environment for the instance.

  • data_path: Directory where the data files will be stored. Defaults to $MONGO_DATA_ROOT.

  • bindIp: MongoDB configuration parameter. See the official documentationarrow-up-right for details.

  • port: MongoDB listening port number.

  • template: MongoDB configuration template file to be used.

Here is the content of the template used in the example. You can of course change this as needed.

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Warning If you want to modify DMK templates, variables must be written as ${VARIABLE} to ensure proper substitution.

Other templates are available, for installation with TLS communication enabled, or for a replica set.

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Creating the instance

After verifying that all templates are correct, run dmk_dbcreate.py. This script will create:

  • The MongoDB instance directory structure.

  • A systemd file named mongod_<instance_name>.service, which has to be copied to /etc/systemd/system.

  • The MongoDB configuration file named <instance_name>.conf.

As instructed, copy the service file to /etc/systemd/system as the root user:

If this is the first MongoDB instance on the server, configure logrotate as instructed, again as root:

You can now reload DMK by running dmk or re-login as mongodb, and load the environment associated with the new instance.

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Securing the MongoDB instance

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You must always secure the MongoDB instances right after their creation !

Connect to the MongoDB instance with ms, and run the following commands :

Example:

In the $MONGO_BASE/admin/$MONGO_INSTANCE/secret directory, create a cred.yaml file where the credentials will be stored.

Change the permissions with chmod 400 cred.yaml. You can now test the credentials with the msp alias.

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Update MongoDB configuration file

Modify the configuration file with vic to include the security.authorization parameter:

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Restart the MongoDB instance

To complete the process of securing your MongoDB instance, restart the instance with mgrestart.

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You have successfully created and secured a MongoDB instance using DMK.

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