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How to perform common administrative tasks in MongoDB

Connecting to the shell​

To connect to the MongoDB shell, simply type mongo as a sudo user:

[root@~]# mongo
MongoDB shell version v4.4.1
connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("2d22b941-8fbf-4fe3-99ed-a52678e22097") }
MongoDB server version: 4.4.1
---
...
>

To exit the shell, type exit.

Connecting with authentication​

To connect to the MongoDB shell with a specific user, use the following syntax:

[root@~]# mongo -u YOURUSER -p --authenticationDatabase admin

Creating a database​

If a database does not exist, MongoDB will automatically create the database when you try to use it:

> use authors
switched to db authors

Though the database doesn't officially exist until you insert data, as below:

> show dbs
admin    0.000GB
config   0.000GB
local    0.000GB
> db.authors.insert({ authorname: "Ursula K. Le Guin"})
WriteResult({ "nInserted" : 1 })
> show dbs
authors 0.000GB
admin   0.000GB
config  0.000GB
local   0.000GB
> db.authors.find()
{ "_id" : ObjectId("5f60a43e73116436bea8c0a4"), "authorname" : "Ursula K. Le Guin" }

Enabling remote access​

warning

Always ensure that the bind address for MongoDB is restricted on your firewall.

To connect to MongoDB from a remote location, you will need to ensure that the bind address is amended to your required IP Address.

  • As a sudo user, edit the MongoDB configuration file to specify the bind address. In this example, we are binding this to 12.34.56.78:
[root@ ~]# vi /etc/mongod.conf
# network interfaces
net:
  port: 27017
  bindIp: 127.0.0.1,12.34.56.78
# Enter 0.0.0.0,:: to bind to all IPv4 and IPv6 addresses or, alternatively, use the net.bindIpAll setting.
  • Restart the service:
[root@]# systemctl restart mongod
note

You may also need to ensure that port 27017 is open to your required location on your software firewall. This falls outside the scope of this tutorial.

Changing the assigned port​

warning

Always ensure that the assigned port for MongoDB is restricted on your firewall.

To change the MongoDB to something non-standard, away from 27017, you will need to edit your MongoDB configuration file.

  • As a sudo user, edit the MongoDB configuration file to specify your new port number:
[root@ ~]# vi /etc/mongod.conf
# network interfaces
net:
#  port: 27017
  port: 27018
  • Restart the service:
[root@]# systemctl restart mongod
note

You may also need to ensure that port 27017 is open to your required location on your software firewall. This falls outside the scope of this tutorial.

Troubleshooting​

Error Logging​

MongoDB logs to the following file upon startup and shutdown, and so is a good place to start when diagnosing startup errors:

/var/log/mongodb/mongod.log

Permissions​

Typically, file ownership and permissions can trip up a MongoDB installation. Be sure to check that the MongoDB data directory is owned by the mongod user:

[root@ ~]# stat /var/lib/mongo
  File: '/var/lib/mongo'
  Size: 4096            Blocks: 8          IO Block: 4096   directory
Device: fd02h/64770d    Inode: 669         Links: 4
Access: (0755/drwxr-xr-x)  Uid: (  977/  mongod)   Gid: (  971/  mongod

If this is not owned by the mongod user, you can correct this with the following command as a sudo user:

[root@ ~]# chown -R mongod: /var/lib/mongo

If using SELinux in enforcing mode, you will need to ensure that the correct SELinux policy is set using the following documentation: