Run-time Database Configuration

Run-time Database Configuration

The command line and configuration file interfaces provide MongoDB administrators with a large number of options and settings for controlling the operation of the database system. This document provides an overview of common configurations and examples of best-practice configurations for common use cases.

While both interfaces provide access to the same collection of options and settings, this document primarily uses the configuration file interface. If you run MongoDB using a control script or installed from a package for your operating system, you likely already have a configuration file located at /etc/mongodb.conf. Confirm this by checking the contents of the /etc/init.d/mongod or /etc/rc.d/mongod script to ensure that the control scripts start the mongod with the appropriate configuration file. To start a MongoDB instance using this configuration issue a command in the following form:

mongod –config /etc/mongodb.conf

mongod -f /etc/mongodb.conf

Modify the values in the /etc/mongodb.conf file on your system to control the configuration of your database instance.

Configure the Database – Consider the following basic configuration:

fork = true

bind_ip = 127.0.0.1

port = 27017

quiet = true

dbpath = /srv/mongodb

logpath = /var/log/mongodb/mongod.log

logappend = true

journal = true

For most standalone servers, this is a sufficient base configuration. It makes several assumptions, but consider the following explanation:

• fork is true, which enables a daemon mode for mongod, which detaches (i.e. “forks”) the MongoDB from the current session and allows you to run the database as a conventional server.
• bind_ip is 127.0.0.1, which forces the server to only listen for requests on the localhost IP. Only bind to secure interfaces that the application-level systems can access with access control provided by system network filtering (i.e. “firewall”). New in version 2.6: mongod installed from official .deb and .rpm packages have the bind_ip configuration set to 127.0.0.1 by default.
• port is 27017, which is the default MongoDB port for database instances. MongoDB can bind to any port. You can also filter access based on port using network filtering tools.
• quiet is true. This disables all but the most critical entries in output/log file. In normal operation this is the preferable operation to avoid log noise. In diagnostic or testing situations, set this value to false. Use setParameter to modify this setting during run time.
• dbPath is /srv/mongodb, which specifies where MongoDB will store its data files. /srv/mongodb and /var/lib/mongodb are popular locations. The user account that mongod runs under will need read and write access to this directory.
• path is /var/log/mongodb/mongod.log which is where mongod will write its output. If you do not set this value, mongod writes all output to standard output (e.g. stdout.)
• logappend is true, which ensures that mongod does not overwrite an existing log file following the server start operation.
• journal.enabled is true, which enables journaling. Journaling ensures single instance write-durability. 64-bit builds of mongod enable journaling by default. Thus, this setting may be redundant.

Given the default configuration, some of these values may be redundant. However, in many situations explicitly stating the configuration increases overall system intelligibility.

Security Considerations – The following collection of configuration options are useful for limiting access to a mongod instance. Consider the following:

bind_ip = 127.0.0.1,10.8.0.10,192.168.4.24

nounixsocket = true

auth = true

Consider the following explanation for these configuration decisions:

• “bind_ip” has three values: 127.0.0.1, the localhost interface; 10.8.0.10, a private IP address typically used for local networks and VPN interfaces; and 192.168.4.24, a private network interface typically used for local networks. Because production MongoDB instances need to be accessible from multiple database servers, it is important to bind MongoDB to multiple interfaces that are accessible from your application servers. At the same time it’s important to limit these interfaces to interfaces controlled and protected at the network layer.
• “nounixsocket” to true disables the UNIX Socket, which is otherwise enabled by default. This limits access on the local system. This is desirable when running MongoDB on systems with shared access, but in most situations has minimal impact.
• “authorization” is true enables the authentication system within MongoDB. If enabled you will need to log in by connecting over the localhost interface for the first time to create user credentials.

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