MongoDB Config Guide: System Log, Network, Security, and Storage Settings

MongoDB Configuration File Explained

System Log Configuration

systemLog:
  verbosity: <int>
  quiet: <boolean>
  traceAllExceptions: <boolean>
  syslogFacility: <string>
  path: <string>
  logAppend: <boolean>
  logRotate: <string>
  destination: <string>
  timeStampFormat: <string>
  component:
    accessControl:
      verbosity: <int>
    command:
      verbosity: <int>

verbosity: Log level, default 0, range 1‑5.

quiet: Suppresses log output; not recommended for production because it can hide troubleshooting information.

traceAllExceptions: Prints detailed information for debugging.

syslogFacility: Syslog facility (default "user"); requires the --syslog option.

path: File system path where logs are stored.

logAppend: When true, logs are appended to the existing file after a restart; default false creates a new file each start.

logRotate: Log rotation method, default "rename". Can be set to "reopen" which follows Linux log rotation; "reopen" must be used with logAppend=true.

destination: Where logs are sent – either a file or syslog.

timeStampFormat: Timestamp format, default "iso8601-local". Options: "iso8601-utc", "ctime".

Process Management

processManagement:
  fork: <boolean>
  pidFilePath: <string>

fork: Run MongoDB as a daemon.

pidFilePath: Location of the PID file.

Network Options

net:
  port: <int>
  bindIp: <string>
  maxIncomingConnections: <int>
  wireObjectCheck: <boolean>
  ipv6: <boolean>
  unixDomainSocket:
    enabled: <boolean>
    pathPrefix: <string>
    filePermissions: <int>
  http:
    enabled: <boolean>
    JSONPEnabled: <boolean>
    RESTInterfaceEnabled: <boolean>
  ssl:
    sslOnNormalPorts: <boolean>
    mode: <string>
    PEMKeyFile: <string>
    PEMKeyPassword: <string>
    clusterFile: <string>
    clusterPassword: <string>
    CAFile: <string>
    CRLFile: <string>
    allowConnectionsWithoutCertificates: <boolean>
    allowInvalidCertificates: <boolean>
    allowInvalidHostnames: <boolean>
    disabledProtocols: <string>
    FIPSMode: <boolean>
  compression:
    compressors: <string>

net.port: Listening port.

net.bindIp: IP address to bind.

net.maxIncomingConnections: Maximum number of simultaneous connections (default 65535).

net.wireObjectCheck: Validates incoming BSON data; default true.

net.ipv6: Enables IPv6; default false.

net.unixDomainSocket.enabled: Enables Unix domain socket; default true.

net.unixDomainSocket.pathPrefix: Directory for socket files (default /tmp).

net.unixDomainSocket.filePermissions: Permissions for socket files (default 0700).

net.http.enabled: HTTP interface; default false and deprecated since version 3.2.

net.http.JSONPEnabled / net.http.RESTInterfaceEnabled: Control JSONP and simple REST API; both deprecated.

net.ssl: SSL/TLS configuration options.

net.compression.compressors: Enables network compression.

Security Settings

security:
  keyFile: <string>
  clusterAuthMode: <string>
  authorization: <string>
  transitionToAuth: <boolean>
  javascriptEnabled: <boolean>
  redactClientLogData: <boolean>
  sasl:
    hostName: <string>
    serviceName: <string>
    saslauthdSocketPath: <string>
  enableEncryption: <boolean>
  encryptionCipherMode: <string>
  encryptionKeyFile: <string>
  kmip:
    keyIdentifier: <string>
    rotateMasterKey: <boolean>
    serverName: <string>
    port: <string>
    clientCertificateFile: <string>
    clientCertificatePassword: <string>
    serverCAFile: <string>
  ldap:
    servers: <string>
    bind:
      method: <string>
      saslMechanism: <string>
      queryUser: <string>
      queryPassword: <string>
      useOSDefaults: <boolean>
    transportSecurity: <string>
    timeoutMS: <int>
    userToDNMapping: <string>
    authz:
      queryTemplate: <string>

security.authorization: Default "disabled"; enables role‑based access control when set to "enabled".

Custom Parameters

setParameter:
  <parameter1>: <value1>
  <parameter2>: <value2>

setParameter: Allows setting arbitrary MongoDB parameters.

Storage Engine Configuration

storage:
  dbPath: <string>
  indexBuildRetry: <boolean>
  repairPath: <string>
  journal:
    enabled: <boolean>
    commitIntervalMs: <num>
  directoryPerDB: <boolean>
  syncPeriodSecs: <int>
  engine: <string>
  mmapv1:
    preallocDataFiles: <boolean>
    nsSize: <int>
    quota:
      enforced: <boolean>
      maxFilesPerDB: <int>
    smallFiles: <boolean>
    journal:
      debugFlags: <int>
      commitIntervalMs: <num>
  wiredTiger:
    engineConfig:
      cacheSizeGB: <number>
      journalCompressor: <string>
      directoryForIndexes: <boolean>
    collectionConfig:
      blockCompressor: <string>
    indexConfig:
      prefixCompression: <boolean>
  inMemory:
    engineConfig:
      inMemorySizeGB: <number>

storage.dbPath: Directory for data files.

storage.indexBuildRetry: If true (default), MongoDB attempts to rebuild incomplete indexes on startup.

storage.repairPath: Temporary directory for --repair files; removed after use.

storage.journal.enabled: Enables journaling; default true on 64‑bit systems.

storage.journal.commitIntervalMs: Maximum time between journal commits (default 100 ms, older default 30 ms).

storage.directoryPerDB: When true, each database gets its own subdirectory under dbPath.

storage.syncPeriodSecs: Interval for syncing data to disk (default 60 s; 0 disables syncing).

storage.engine: Storage engine, default "wiredTiger".

storage.mmapv1.preallocDataFiles: Pre‑allocates data files; default true.

storage.mmapv1.nsSize: Default 16 MB per namespace file.

storage.mmapv1.quota.enforced: Enforces a limit on the number of data files per database.

storage.mmapv1.quota.maxFilesPerDB: Maximum data files per database (default 8).

storage.mmapv1.smallFiles: Uses smaller default file sizes; default false.

storage.mmapv1.journal.debugFlags: Debug feature, not recommended for production.

storage.wiredTiger.engineConfig.cacheSizeGB: Maximum internal cache size (up to half of RAM minus 1 GB, max 256 GB).

storage.wiredTiger.engineConfig.journalCompressor: Compression for journal data (none, snappy, zlib).

storage.wiredTiger.engineConfig.directoryForIndexes: When true, creates an "index" subdirectory for indexes.

storage.wiredTiger.collectionConfig.blockCompressor: Data compression format (none, snappy, zlib).

storage.wiredTiger.indexConfig.prefixCompression: Enables prefix compression for index data; default true.

storage.inMemory.engineConfig.inMemorySizeGB: Maximum memory allocated for the in‑memory engine (default half of RAM minus 1 GB).

Slow Query Profiling

operationProfiling:
  slowOpThresholdMs: <int>
  mode: <string>

operationProfiling.slowOpThresholdMs: Threshold in milliseconds for logging slow operations (default 100 ms).

operationProfiling.mode: Profiling level – "off" (disabled), "slowOp" (only slow ops), or "all" (all operations).

Replication Options

replication:
  oplogSizeMB: <int>
  replSetName: <string>
  secondaryIndexPrefetch: <string>
  enableMajorityReadConcern: <boolean>

replication.oplogSizeMB: Maximum size of the oplog; typically 5 % of disk space.

replication.replSetName: Name of the replica set.

replication.secondaryIndexPrefetch: For mmapv1 engine; default "all". Loads all indexes into memory before applying oplog entries.

replication.enableMajorityReadConcern: Enables majority read concern; default false.

Sharding Configuration

sharding:
  clusterRole: <string>
  archiveMovedChunks: <boolean>

sharding.clusterRole: Defines the node role – "configsvr" for config servers or "shardsvr" for shard servers.

sharding.archiveMovedChunks: When false (default), documents moved out of a shard are not archived.

Mongos Parameters

replication:
  localPingThresholdMs: <int>

sharding:
  configDB: <string>

replication.localPingThresholdMs: Default 15 ms; mongos uses this to forward client requests to the secondary with the lowest latency.

sharding.configDB: List of config server addresses.

MongoDB supports three storage engines: mmapv1, WiredTiger, and inMemory.