Why is security.authorization off by default in the fields, and should I enable it?

MongoDB ships with authorization disabled by default so a fresh local instance is easy to connect to, but any instance reachable outside a fully trusted local machine should have security.authorization: enabled set, which requires clients to authenticate before running most commands.

What does the WiredTiger cache size actually control?

storage.wiredTiger.engineConfig.cacheSizeGB sets the size of WiredTiger's internal cache, which holds frequently accessed data and indexes in memory. MongoDB's own guidance is roughly 50% of (RAM minus 1GB), left as a default if unset, but setting it explicitly is important on shared or containerized hosts where MongoDB can't accurately detect total system memory.

What happens if I enable replication without setting up the other members?

Setting replication.replSetName in mongod.conf tells that mongod instance to run in replica set mode, but you still need to connect to it and run rs.initiate() (and rs.add() for additional members) to actually form the replica set; the config alone doesn't create it.

Why is this output YAML instead of the older key=value format?

Modern MongoDB (3.2+) uses YAML-formatted configuration files by default, replacing the older flat key=value format. YAML groups related settings under nested sections like net, security, storage, and replication, which this tool mirrors exactly.

MongoDB Config Generator - mongod.conf YAML

Overview

Introduction

A mongod.conf file is YAML, which means getting the nesting right under net, security, storage, and replication matters as much as picking the right values, a single misplaced indent silently changes which section a setting lands in.

This tool builds that YAML from a form, toggling entire blocks like replication on or off rather than leaving stray empty sections, so the output is both correctly indented and free of dead configuration.

What Is MongoDB Config Generator?

A generator for mongod.conf covering network binding (net.bindIp, net.port), authorization (security.authorization), WiredTiger cache sizing (storage.wiredTiger.engineConfig.cacheSizeGB), an optional replica set name (replication.replSetName), and the log file path (systemLog.path).

The replication block is entirely conditional, when the replica set toggle is off, no replication: section appears in the output at all.

How MongoDB Config Generator Works

Each field is emitted under its correct nested YAML section using consistent two-space indentation: net, security, storage.wiredTiger.engineConfig, and systemLog are always present, while replication only appears when explicitly enabled.

The authorization toggle emits security.authorization as either the literal string 'enabled' or 'disabled', matching the exact values MongoDB's config parser expects rather than a boolean.

When To Use MongoDB Config Generator

Use it when provisioning a new standalone or replica-set-bound MongoDB instance and you want a correctly nested mongod.conf without hand-writing YAML indentation.

It's also useful for quickly producing a consistent config template across several replica set members that differ only in their bindIp or replSetName.

Features

Advantages

Guarantees correct YAML nesting for every section, eliminating the most common mongod.conf error: a misplaced indent silently moving a setting under the wrong parent key.
Omits the entire replication: block when it isn't needed, instead of leaving an empty or commented-out section.
Emits security.authorization using MongoDB's exact expected string values rather than a boolean that wouldn't parse correctly.

Limitations

Only covers the config file itself, it doesn't run rs.initiate() or otherwise form a replica set for you.
Doesn't cover sharding-specific settings (mongos, config servers, shard configuration); it targets standalone and single-replica-set mongod instances.
Doesn't validate that the cache size you enter fits within the host's actual available memory.

Examples

A replica-set member with authorization enabled

Input

bindIp: 0.0.0.0, port: 27017, authorization: enabled, cacheSizeGB: 4, replSetName: rs0, systemLog.path: /var/log/mongodb/mongod.log

Output

net:
  bindIp: 0.0.0.0
  port: 27017

security:
  authorization: enabled

storage:
  wiredTiger:
    engineConfig:
      cacheSizeGB: 4

replication:
  replSetName: rs0

systemLog:
  destination: file
  path: /var/log/mongodb/mongod.log

The replication: block appears because the replica set toggle was enabled; leaving it off removes those two lines entirely.

Best Practices & Notes

Best Practices

Always set security.authorization: enabled on any instance reachable from outside a fully trusted local machine.
Set cacheSizeGB explicitly on containerized or shared hosts, since MongoDB's automatic default can overestimate available memory in those environments.
Use a descriptive replSetName (e.g. matching your environment name) so it's unambiguous which cluster a given config belongs to.

Developer Notes

Output is hand-built YAML (no YAML library dependency), using a fixed 2-space indentation scheme matching MongoDB's own documentation examples; the replication section is only pushed onto the output when the replica set toggle is enabled, and security.authorization is emitted as the literal string 'enabled' or 'disabled' since that's the exact value MongoDB's YAML config parser requires, not a YAML boolean.

MongoDB Config Generator Use Cases

Bootstrapping mongod.conf for a new standalone MongoDB instance
Producing consistent config templates for each member of a new replica set
Generating a config snippet to confirm authorization and cache settings before a production rollout

Common Mistakes

Leaving security.authorization disabled on an instance that's reachable beyond localhost.
Setting replSetName in config but never actually running rs.initiate() against the instance, leaving it running as a lone, unconfigured replica set member.
Mis-indenting nested YAML by hand when editing the output afterward, which silently moves a setting to the wrong parent section.

Tips

Generate one config per replica set member, changing only bindIp and any host-specific cacheSizeGB, keeping replSetName identical across all of them.
Pair the authorization toggle with creating an admin user via mongosh before restarting mongod with authorization enabled, otherwise you can lock yourself out.

MongoDB Config Generator