mongod

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Synopsis

mongod is the primary daemon process for the MongoDB system. It handles data requests, manages data access, and performs background management operations.

This document provides a complete overview of all command line options for mongod. These command line options are primarily useful for testing: In common operation, use the configuration file options to control the behavior of your database.

Options

Core Options

mongod
--help, -h

Returns information on the options and use of mongod.

--version

Returns the mongod release number.

--config <filename>, -f <filename>

Specifies a configuration file for runtime configuration options. The configuration file is the preferred method for runtime configuration of mongod. The options are equivalent to the command-line configuration options. See Configuration File Options for more information.

Ensure the configuration file uses ASCII encoding. The mongod instance does not support configuration files with non-ASCII encoding, including UTF-8.

--verbose, -v

Increases the amount of internal reporting returned on standard output or in log files. Increase the verbosity with the -v form by including the option multiple times, (e.g. -vvvvv.)

--quiet

Runs mongod in a quiet mode that attempts to limit the amount of output.

This option suppresses:

  • output from database commands
  • replication activity
  • connection accepted events
  • connection closed events
--port <port>

Default: 27017

Specifies the TCP port on which the MongoDB instance listens for client connections.

--bind_ip <ip address>

Default: All interfaces.

Changed in version 2.6.0: The deb and rpm packages include a default configuration file (/etc/mongod.conf) that sets --bind_ip to 127.0.0.1.

Specifies the IP address that mongod binds to in order to listen for connections from applications. You may attach mongod to any interface. When attaching mongod to a publicly accessible interface, ensure that you have implemented proper authentication and firewall restrictions to protect the integrity of your database.

--ipv6

Removed in version 3.0.

Enables IPv6 support and allows mongod to connect to the MongoDB instance using an IPv6 network. Prior to MongoDB 3.0, you had to specify --ipv6 to use IPv6. In MongoDB 3.0 and later, IPv6 is always enabled.

--maxConns <number>

The maximum number of simultaneous connections that mongod will accept. This setting has no effect if it is higher than your operating system’s configured maximum connection tracking threshold.

Do not assign too low of a value to this option, or you will encounter errors during normal application operation.

Note

Changed in version 2.6: MongoDB removed the upward limit on the maxIncomingConnections setting.

--logpath <path>

Sends all diagnostic logging information to a log file instead of to standard output or to the host’s syslog system. MongoDB creates the log file at the path you specify.

By default, MongoDB will move any existing log file rather than overwrite it. To instead append to the log file, set the --logappend option.

--syslog

Sends all logging output to the host’s syslog system rather than to standard output or to a log file. , as with --logpath.

The --syslog option is not supported on Windows.

--syslogFacility <string>

Default: user

Specifies the facility level used when logging messages to syslog. The value you specify must be supported by your operating system’s implementation of syslog. To use this option, you must enable the --syslog option.

--logappend

Appends new entries to the end of the existing log file when the mongod instance restarts. Without this option, mongod will back up the existing log and create a new file.

--logRotate <string>

Default: rename

New in version 3.0.0.

Determines the behavior for the logRotate command. Specify either rename or reopen:

  • rename renames the log file.

  • reopen closes and reopens the log file following the typical Linux/Unix log rotate behavior. Use reopen when using the Linux/Unix logrotate utility to avoid log loss.

    If you specify reopen, you must also use --logappend.

--timeStampFormat <string>

Default: iso8601-local

The time format for timestamps in log messages. Specify one of the following values:

Value Description
ctime Displays timestamps as Wed Dec 31 18:17:54.811.
iso8601-utc Displays timestamps in Coordinated Universal Time (UTC) in the ISO-8601 format. For example, for New York at the start of the Epoch: 1970-01-01T00:00:00.000Z
iso8601-local Displays timestamps in local time in the ISO-8601 format. For example, for New York at the start of the Epoch: 1969-12-31T19:00:00.000-0500
--traceExceptions

For internal diagnostic use only.

--pidfilepath <path>

Specifies a file location to hold the process ID of the mongod process where mongod will write its PID. This is useful for tracking the mongod process in combination with the --fork option. Without a specified --pidfilepath option, the process creates no PID file.

--keyFile <file>

Specifies the path to a key file that stores the shared secret that MongoDB instances use to authenticate to each other in a sharded cluster or replica set. --keyFile implies --auth. See Internal Authentication for more information.

--setParameter <options>

Specifies one of the MongoDB parameters described in MongoDB Server Parameters. You can specify multiple setParameter fields.

--httpinterface

Deprecated since version 3.2: HTTP interface for MongoDB

Enables the HTTP interface. Enabling the interface can increase network exposure.

Leave the HTTP interface disabled for production deployments. If you do enable this interface, you should only allow trusted clients to access this port. See Firewalls.

Note

  • While MongoDB Enterprise does support Kerberos authentication, Kerberos is not supported in HTTP status interface in any version of MongoDB.

New in version 2.6.

--nounixsocket

Disables listening on the UNIX domain socket. --nounixsocket applies only to Unix-based systems.

The mongod process always listens on the UNIX socket unless one of the following is true:

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.

--unixSocketPrefix <path>

Default: /tmp

The path for the UNIX socket. --unixSocketPrefix applies only to Unix-based systems.

If this option has no value, the mongod process creates a socket with /tmp as a prefix. MongoDB creates and listens on a UNIX socket unless one of the following is true:

--filePermissions <path>

Default: 0700

Sets the permission for the UNIX domain socket file.

--filePermissions applies only to Unix-based systems.

--fork

Enables a daemon mode that runs the mongod process in the background. By default mongod does not run as a daemon: typically you will run mongod as a daemon, either by using --fork or by using a controlling process that handles the daemonization process (e.g. as with upstart and systemd).

--auth

Enables authorization to control user’s access to database resources and operations. When authorization is enabled, MongoDB requires all clients to authenticate themselves first in order to determine the access for the client.

Configure users via the mongo shell. If no users exist, the localhost interface will continue to have access to the database until you create the first user.

See Security for more information.

--noauth

Disables authentication. Currently the default. Exists for future compatibility and clarity.

--transitionToAuth

New in version 3.4: Allows the mongod to accept and create authenticated and non-authenticated connections to and from other mongod and mongos instances in the deployment. Used for performing rolling transition of replica sets or sharded clusters from a no-auth configuration to internal authentication. Requires specifying a internal authentication mechanism such as --keyfile.

For example, if using keyfiles for internal authentication, the mongod creates an authenticated connection with any mongod or mongos in the deployment using a matching keyfile. If the security mechanisms do not match, the mongod utilizes a non-authenticated connection instead.

A mongod running with --transitionToAuth does not enforce user access controls. Users may connect to your deployment without any access control checks and perform read, write, and administrative operations.

Note

A mongod running with internal authentication and without --transitionToAuth requires clients to connect using user access controls. Update clients to connect to the mongod using the appropriate user prior to restarting mongod without --transitionToAuth.

--jsonp

Permits JSONP access via an HTTP interface. Enabling the interface can increase network exposure. The --jsonp option enables the HTTP interface, even if the HTTP interface option is disabled.

Deprecated since version 3.2: HTTP interface for MongoDB

--rest

Enables the simple REST API. Enabling the REST API enables the HTTP interface, even if the HTTP interface option is disabled, and as a result can increase network exposure.

Deprecated since version 3.2: HTTP interface for MongoDB

--slowms <integer>

Default: 100

The threshold in milliseconds at which the database profiler considers a query slow. MongoDB records all slow queries to the log, even when the database profiler is off. When the profiler is on, it writes to the system.profile collection. See the profile command for more information on the database profiler.

--profile <level>

Default: 0

Changes the level of database profiling, which inserts information about operation performance into the system.profile collection. Specify one of the following levels:

Level Setting
0 Off. No profiling.
1 On. Only includes slow operations.
2 On. Includes all operations.

Database profiling can impact database performance. Enable this option only after careful consideration.

--cpu

Forces the mongod process to report the percentage of CPU time in write lock, every four seconds.

--sysinfo

Returns diagnostic system information and then exits. The information provides the page size, the number of physical pages, and the number of available physical pages.

--noscripting

Disables the scripting engine.

--notablescan

Forbids operations that require a collection scan. See notablescan for additional information.

--shutdown

The --shutdown option cleanly and safely terminates the mongod process. When invoking mongod with this option you must set the --dbpath option either directly or by way of the configuration file and the --config option.

The --shutdown option is available only on Linux systems.

--redactClientLogData

New in version 3.4: Available in MongoDB Enterprise only.

A mongod running with --redactClientLogData redacts any message accompanying a given log event before logging. This prevents the mongod from writing potentially sensitive data stored on the database to the diagnostic log. Metadata such as error or operation codes, line numbers, and source file names are still visible in the logs.

Use --redactClientLogData in conjunction with encryption to assist compliance with regulatory requirements.

For example, a MongoDB deployment might store Personally Identifiable Information (PII) in one or more collections. The mongod logs events such as those related to CRUD operations, sharding metadata, etc. It is possible that the mongod may expose PII as a part of these logging operations. A mongod running with --redactClientLogData removes any message accompanying these events before being output to the log, effectively removing the PII.

Diagnostics on a mongod running with --redactClientLogData may be more difficult due to the lack of data related to a log event. See the process logging manual page for an example of the effect of --redactClientLogData on log output.

You can enable or disable log redaction on a running mongod using the setParameter database command.

db.getSiblingDB("admin").runCommand(
  { setParameter: { redactClientLogData : "true | false" } }
)

LDAP Authentication or Authorization Options

--ldapServers <host1>:<port>,<host2>:<port>,...,<hostN>:<port>

New in version 3.4: Available in MongoDB Enterprise only.

Takes a quote-enclosed comma-separated string of one or more LDAP servers, each in host:port format. mongod executes LDAP operations against these servers to authenticate users or determine what actions a user is authorized to perform on a given database.

This setting can be configured on a running mongod using setParameter.

If unset, mongod cannot use LDAP authentication or authorization.

--ldapQueryUser <string>

New in version 3.4: Available in MongoDB Enterprise only.

The identity with which mongod binds as, when connecting to or performing queries on an LDAP server.

Only required if any of the following are true:

You must use --ldapQueryUser with --ldapQueryPassword.

If unset, mongod will not attempt to bind to the LDAP server.

This setting can be configured on a running mongod using setParameter.

Note

Windows MongoDB deployments can use --ldapBindWithOSDefaults instead of --ldapQueryUser and --ldapQueryPassword. You cannot specify both --ldapQueryUser and --ldapBindWithOSDefaults at the same time.

--ldapQueryPassword <string>

New in version 3.4: Available in MongoDB Enterprise only.

The password used to bind to an LDAP server when using --ldapQueryUser. You must use --ldapQueryPassword with --ldapQueryUser.

If unset, mongod will not attempt to bind to the LDAP server.

This setting can be configured on a running mongod using setParameter.

Note

Windows MongoDB deployments can use --ldapBindWithOSDefaults instead of --ldapQueryPassword and --ldapQueryPassword. You cannot specify both --ldapQueryPassword and --ldapBindWithOSDefaults at the same time.

--ldapBindWithOSDefaults <bool>

Default: False

New in version 3.4: Available in MongoDB Enterprise for the Windows platform only.

Allows mongod to authenticate, or bind, using your Windows login credentials when connecting to the LDAP server.

Only required if:

Use --ldapBindWithOSDefaults to replace --ldapQueryUser and --ldapQueryPassword.

--ldapBindMethod <string>

Default: simple

New in version 3.4: Available in MongoDB Enterprise only.

The method mongod uses to authenticate to an LDAP server. Use with --ldapQueryUser and --ldapQueryPassword to connect to the LDAP server.

--ldapBindMethod supports the following values:

  • simple - mongod uses simple authentication.
  • sasl - mongod uses SASL protocol for authentication

If you specify sasl, you can configure the available SASL mechanisms using . mongod defaults to using DIGEST-MD5 mechanism.

--ldapBindSASLMechanisms <string>

Default: DIGEST-MD5

New in version 3.4: Available in MongoDB Enterprise only.

A comma-separated list of SASL mechanisms mongod can use when authenticating to the LDAP server. The mongod and the LDAP server must agree on at least one mechanism.

Set --ldapBindMethod to sasl to use this option.

Note

A complete list of SASL mechanisms is out of scope for this documentation. See the IANA list of SASL mechanisms, as well as the documentation for your LDAP service.

--ldapTransportSecurity <string>

Default: tls

New in version 3.4: Available in MongoDB Enterprise only.

By default, mongod creates a TLS/SSL secured connection to the LDAP server.

For Linux deployments, you must configure the appropriate TLS Options in /etc/openldap/ldap.conf file. Your operating system’s package manager creates this file as part of the MongoDB Enterprise installation, via the libldap dependency. See the documentation for TLS Options in the ldap.conf OpenLDAP documentation for more complete instructions.

For Windows deployment, you must add the LDAP server CA certificates to the Windows certificate management tool. The exact name and functionality of the tool may vary depending on operating system version. Please see the documentation for your version of Windows for more information on certificate management.

Set --ldapTransportSecurity to none to disable TLS/SSL between mongod and the LDAP server.

Warning

Setting --ldapTransportSecurity to none transmits plaintext information and possibly credentials between mongod and the LDAP server.

--ldapTimeoutMS <long>

Default: 10000

New in version 3.4: Available in MongoDB Enterprise only.

The amount of time in milliseconds mongod should wait for an LDAP server to respond to a request.

Increasing the value of --ldapTimeoutMS may prevent connection failure between the MongoDB server and the LDAP server, if the source of the failure is a connection timeout. Decreasing the value of --ldapTimeoutMS reduces the time MongoDB waits for a response from the LDAP server.

This setting can be configured on a running mongod using setParameter.

--ldapUserToDNMapping <string>

New in version 3.4: Available in MongoDB Enterprise only.

Maps the username provided to mongod for authentication to a LDAP Distinguished Name (DN). You may need to use --ldapUserToDNMapping to transform a username into an LDAP DN in the following scenarios:

  • Performing LDAP authentication with simple LDAP binding, where users authenticate to MongoDB with usernames that are not full LDAP DNs.
  • Using an LDAP authorization query template that requires a DN.
  • Transforming the usernames of clients authenticating to Mongo DB using different authentication mechanisms (e.g. x.509, kerberos) to a full LDAP DN for authorization.

--ldapUserToDNMapping expects a quote-enclosed JSON-string representing an ordered array of documents. Each document contains a regular expression match and either a substitution or ldapQuery template used for transforming the incoming username.

Each document in the array has the following form:

{
  match: "<regex>"
  substitution: "<LDAP DN>" | ldapQuery: "<LDAP Query>"
}
Field Description Example
match An ECMAScript-formatted regular expression (regex) to match against a provided username. Each parenthesis-enclosed section represents a regex capture group used by substitution or ldapQuery. "(.+)ENGINEERING" "(.+)DBA"
substitution An LDAP distinguished name (DN) formatting template that converts the authentication name matched by the match regex into a LDAP DN. Each curly bracket-enclosed numeric value is replaced by the corresponding regex capture group extracted from the authentication username via the match regex. "cn={0},ou=engineering, dc=example,dc=com"
ldapQuery A LDAP query formatting template that inserts the authentication name matched by the match regex into an LDAP query URI encoded respecting RFC4515 and RFC4516. Each curly bracket-enclosed numeric value is replaced by the corresponding regex capture group extracted from the authentication username via the match expression. mongod executes the query against the LDAP server to retrieve the LDAP DN for the authenticated user. mongod requires exactly one returned result for the transformation to be successful, or mongod skips this transformation. "ou=engineering,dc=example, dc=com??one?(user={0})"

For each document in the array, you must use either substitution or ldapQuery. You cannot specify both in the same document.

When performing authentication or authorization, mongod steps through each document in the array in the given order, checking the authentication username against the match filter. If a match is found, mongod applies the transformation and uses the output for authenticating the user. mongod does not check the remaining documents in the array.

If the given document does not match the provided authentication name, or the transformation described by the document fails, mongod continues through the list of documents to find additional matches. If no matches are found in any document, mongod returns an error.

Example

The following shows two transformation documents. The first document matches against any string ending in @ENGINEERING, placing anything preceeding the suffix into a regex capture group. The second document matches against any string ending in @DBA, placing anything preceeding the suffix into a regex capture group.

Important

You must pass the array to --ldapUserToDNMapping as a string.

"[
   {
      match: "(.+)@ENGINEERING.EXAMPLE.COM",
      substitution: "cn={0},ou=engineering,dc=example,dc=com"
   },
   {
      match: "(.+)@DBA.EXAMPLE.COM",
      ldapQuery: "ou=dba,dc=example,dc=com??one?(user={0})"

   }

]"

A user with username alice@ENGINEERING.EXAMPLE.COM matches the first document. The regex capture group {0} corresponds to the string alice. The resulting output is the DN "cn=alice,ou=engineering,dc=example,dc=com".

A user with username bob@DBA.EXAMPLE.COM matches the second document. The regex capture group {0} corresponds to the string bob. The resulting output is the LDAP query "ou=dba,dc=example,dc=com??one?(user=bob)". mongod executes this query against the LDAP server, returning the result "cn=bob,ou=dba,dc=example,dc=com".

If --ldapUserToDNMapping is unset, mongod applies no transformations to the username when attempting to authenticate or authorize a user against the LDAP server.

This setting can be configured on a running mongod using the setParameter database command.

Note

An explanation of RFC4515, RFC4516 or LDAP queries is out of scope for the MongoDB Documentation. Please review the RFC directly or use your preferred LDAP resource.

--ldapAuthzQueryTemplate <string>

New in version 3.4: Available in MongoDB Enterprise only.

A relative LDAP query URL formatted conforming to RFC4515 and RFC4516 that mongod executes to obtain the LDAP groups to which the authenticated user belongs to. The query is relative to the host or hosts specified in --ldapServer.

Use the {USER} placeholder in the URL to substitute the authenticated username, or the transformed username if a username mapping is specified.

When constructing the query URL, ensure that the order of LDAP parameters respects RFC4516:

[ dn  [ ? [attributes] [ ? [scope] [ ? [filter] [ ? [Extensions] ] ] ] ] ]

If your query includes an attribute, mongod assumes that the query retrieves a the DNs which this entity is member of.

If your query does not include an attribute, mongod assumes the query retrieves all entities which the user is member of.

For each LDAP DN returned by the query, mongod assigns the authorized user a corresponding role on the admin database. If a role on the on the admin database exactly matches the DN, mongod grants the user the roles and privileges assigned to that role. See the db.createRole() method for more information on creating roles.

Example

This LDAP query returns any groups listed in the LDAP user object’s memberOf attribute.

"{USER}?memberOf?base"

Your LDAP configuration may not include the memberOf attribute as part of the user schema, may possess a different attribute for reporting group membership, or may not track group membership through attributes. Configure your query with respect to your own unique LDAP configuration.

If unset, mongod cannot authorize users using LDAP.

This setting can be configured on a running mongod using the setParameter database command.

Note

An explanation of RFC4515, RFC4516 or LDAP queries is out of scope for the MongoDB Documentation. Please review the RFC directly or use your preferred LDAP resource.

Storage Options

--storageEngine string

Default: wiredTiger

New in version 3.0.

Changed in version 3.2: Starting in MongoDB 3.2, wiredTiger is the default.

Specifies the storage engine for the mongod database. Available values include:

Value Description
mmapv1 To specify the MMAPv1 Storage Engine.
wiredTiger To specify the WiredTiger Storage Engine.
inMemory

To specify the In-Memory Storage Engine.

New in version 3.2: Available in MongoDB Enterprise only.

If you attempt to start a mongod with a --dbpath that contains data files produced by a storage engine other than the one specified by --storageEngine, mongod will refuse to start.

--dbpath <path>

Default: /data/db on Linux and OS X, \data\db on Windows

The directory where the mongod instance stores its data.

If you installed MongoDB using a package management system, check the /etc/mongod.conf file provided by your packages to see the directory is specified.

Changed in version 3.0: The files in --dbpath must correspond to the storage engine specified in --storageEngine. If the data files do not correspond to --storageEngine, mongod will refuse to start.

--directoryperdb

Uses a separate directory to store data for each database. The directories are under the --dbpath directory, and each subdirectory name corresponds to the database name.

Changed in version 3.0: To change the --directoryperdb option for existing deployments, you must restart the mongod instances with the new --directoryperdb value and a new data directory (--dbpath <new path>), and then repopulate the data.

  • For standalone instances, you can use mongodump on the existing instance, stop the instance, restart with the new --directoryperdb value and a new data directory, and use mongorestore to populate the new data directory.
  • For replica sets, you can update in a rolling manner by stopping a secondary member, restart with the new --directoryperdb value and a new data directory, and use initial sync to populate the new data directory. To update all members, start with the secondary members first. Then step down the primary, and update the stepped-down member.

Not available for mongod instances that use the in-memory storage engine.

--noIndexBuildRetry

Stops the mongod from rebuilding incomplete indexes on the next start up. This applies in cases where the mongod restarts after it has shut down or stopped in the middle of an index build. In such cases, the mongod always removes any incomplete indexes, and then also, by default, attempts to rebuild them. To stop the mongod from rebuilding incomplete indexes on start up, include this option on the command-line.

Not available for mongod instances that use the in-memory storage engine.

--noprealloc

Deprecated since version 2.6.

Disables the preallocation of data files. Currently the default. Exists for future compatibility and clarity.

--nssize <value>

Default: 16

Specifies the default size for namespace files, which are files that end in .ns. Each collection and index counts as a namespace.

Use this setting to control size for newly created namespace files. This option has no impact on existing files. The maximum size for a namespace file is 2047 megabytes. The default value of 16 megabytes provides for approximately 24,000 namespaces.

--quota

Enables a maximum limit for the number data files each database can have. When running with the --quota option, MongoDB has a maximum of 8 data files per database. Adjust the quota with --quotaFiles.

--quotaFiles <number>

Default: 8

Modifies the limit on the number of data files per database. --quotaFiles option requires that you set --quota.

--smallfiles

Sets MongoDB to use a smaller default file size. The --smallfiles option reduces the initial size for data files and limits the maximum size to 512 megabytes. --smallfiles also reduces the size of each journal file from 1 gigabyte to 128 megabytes. Use --smallfiles if you have a large number of databases that each holds a small quantity of data.

The --smallfiles option can lead the mongod instance to create a large number of files, which can affect performance for larger databases.

--syncdelay <value>

Default: 60

Controls how much time can pass before MongoDB flushes data to the data files via an fsync operation.

Do not set this value on production systems. In almost every situation, you should use the default setting.

Warning

If you set --syncdelay to 0, MongoDB will not sync the memory mapped files to disk.

The mongod process writes data very quickly to the journal and lazily to the data files. --syncdelay has no effect on the journal files or journaling.

The serverStatus command reports the background flush thread’s status via the backgroundFlushing field.

Not available for mongod instances that use the in-memory storage engine.

--upgrade

Upgrades the on-disk data format of the files specified by the --dbpath to the latest version, if needed.

This option only affects the operation of the mongod if the data files are in an old format.

In most cases you should not set this value, so you can exercise the most control over your upgrade process. See the MongoDB release notes (on the download page) for more information about the upgrade process.

--repair

Runs a repair routine on all databases. This is equivalent to shutting down and running the repairDatabase database command on all databases.

Warning

During normal operations, only use the repairDatabase command and wrappers including db.repairDatabase() in the mongo shell and mongod --repair, to compact database files and/or reclaim disk space. Be aware that these operations remove and do not save any corrupt data during the repair process.

If you are trying to repair a replica set member, and you have access to an intact copy of your data (e.g. a recent backup or an intact member of the replica set), you should restore from that intact copy, and not use repairDatabase.

When using journaling, there is almost never any need to run repairDatabase. In the event of an unclean shutdown, the server will be able to restore the data files to a pristine state automatically.

Changed in version 2.1.2.

If you run the repair option and have data in a journal file, the mongod instance refuses to start. In these cases you should start the mongod without the --repair option, which allows the mongod to recover data from the journal. This completes more quickly and is more likely to produce valid data files. To continue the repair operation despite the journal files, shut down the mongod cleanly and restart with the --repair option.

The --repair option copies data from the source data files into new data files in the repairPath and then replaces the original data files with the repaired data files.

--repairpath <path>

Default: A _tmp_repairDatabase_<num> directory under the dbPath.

Specifies a working directory that MongoDB will use during the --repair operation. When --repair completes, the --repairpath directory is empty, and dbPath contains the repaired files.

The --repairpath must be within the dbPath. You can specify a symlink to --repairpath to use a path on a different file system.

Only available for mongod instance using the MMAPv1 storage engine.

--journal

Enables the durability journal to ensure data files remain valid and recoverable. This option applies only when you specify the --dbpath option. The mongod enables journaling by default on 64-bit builds of versions after 2.0.

Not available for mongod instances that use the in-memory storage engine.

If any voting member of a replica set runs without journaling (i.e. either runs an in-memory storage engine or runs with journaling disabled), you must set writeConcernMajorityJournalDefault to false.

--nojournal

Disables the durability journaling. The mongod instance enables journaling by default in 64-bit versions after v2.0.

Not available for mongod instances that use the in-memory storage engine.

--journalOptions <arguments>

Provides functionality for testing. Not for general use, and will affect data file integrity in the case of abnormal system shutdown.

Not available for mongod instances that use the in-memory storage engine.

--journalCommitInterval <value>

Default: 100 or 30

Changed in version 3.2.

The maximum amount of time in milliseconds that the mongod process allows between journal operations. Values can range from 1 to 500 milliseconds. Lower values increase the durability of the journal, at the expense of disk performance. The default journal commit interval is 100 milliseconds.

On MMAPv1, if the journal is on a different block device (e.g. physical volume, RAID device, or LVM volume) than the data files, the default journal commit interval is 30 milliseconds. Additionally, on MMAPv1, when a write operation with j:true is pending, mongod will reduce commitIntervalMs to a third of the set value.

On WiredTiger, the default journal commit interval is 100 milliseconds. Additionally, a write with j:true will cause an immediate sync of the journal.

Not available for mongod instances that use the in-memory storage engine.

WiredTiger Options

--wiredTigerCacheSizeGB float

Defines the maximum size of the internal cache that WiredTiger will use for all data.

Changed in version 3.4: Values can range from 256MB to 10TB and can be a float. In addition, the default value has also changed.

Starting in 3.4, the WiredTiger internal cache, by default, will use the larger of either:

  • 50% of RAM minus 1 GB, or
  • 256 MB.

Avoid increasing the WiredTiger internal cache size above its default value.

With WiredTiger, MongoDB utilizes both the WiredTiger internal cache and the filesystem cache.

Via the filesystem cache, MongoDB automatically uses all free memory that is not used by the WiredTiger cache or by other processes. Data in the filesystem cache is compressed.

Note

The --wiredTigerCacheSizeGB limits the size of the WiredTiger internal cache. The operating system will use the available free memory for filesystem cache, which allows the compressed MongoDB data files to stay in memory. In addition, the operating system will use any free RAM to buffer file system blocks and file system cache.

To accommodate the additional consumers of RAM, you may have to decrease WiredTiger internal cache size.

The default WiredTiger internal cache size value assumes that there is a single mongod instance per machine. If a single machine contains multiple MongoDB instances, then you should decrease the setting to accommodate the other mongod instances.

If you run mongod in a container (e.g. lxc, cgroups, Docker, etc.) that does not have access to all of the RAM available in a system, you must set --wiredTigerCacheSizeGB to a value less than the amount of RAM available in the container. The exact amount depends on the other processes running in the container.

--wiredTigerJournalCompressor <compressor>

Default: snappy

New in version 3.0.0.

Specifies the type of compression to use to compress WiredTiger journal data.

Available compressors are:

--wiredTigerDirectoryForIndexes

New in version 3.0.0.

When you start mongod with --wiredTigerDirectoryForIndexes, mongod stores indexes and collections in separate subdirectories under the data (i.e. --dbpath`) directory. Specifically, mongod stores the indexes in a subdirectory named index and the collection data in a subdirectory named collection.

By using a symbolic link, you can specify a different location for the indexes. Specifically, when mongod instance is not running, move the index subdirectory to the destination and create a symbolic link named index under the data directory to the new destination.

--wiredTigerCollectionBlockCompressor <compressor>

Default: snappy

New in version 3.0.0.

Specifies the default type of compression to use to compress collection data. You can override this on a per-collection basis when creating collections.

Available compressors are:

--wiredTigerCollectionBlockCompressor affects all collections created. If you change the value of --wiredTigerCollectionBlockCompressor on an existing MongoDB deployment, all new collections will use the specified compressor. Existing collections will continue to use the compressor specified when they were created, or the default compressor at that time.

--wiredTigerIndexPrefixCompression <boolean>

Default: true

New in version 3.0.0.

Enables or disables prefix compression for index data.

Specify true for --wiredTigerIndexPrefixCompression to enable prefix compression for index data, or false to disable prefix compression for index data.

The --wiredTigerIndexPrefixCompression setting affects all indexes created. If you change the value of --wiredTigerIndexPrefixCompression on an existing MongoDB deployment, all new indexes will use prefix compression. Existing indexes are not affected.

Replication Options

--replSet <setname>

Configures replication. Specify a replica set name as an argument to this set. All hosts in the replica set must have the same set name.

If your application connects to more than one replica set, each set should have a distinct name. Some drivers group replica set connections by replica set name.

--oplogSize <value>

Specifies a maximum size in megabytes for the replication operation log (i.e., the oplog). The mongod process creates an oplog based on the maximum amount of space available. For 64-bit systems, the oplog is typically 5% of available disk space. Once the mongod has created the oplog for the first time, changing the --oplogSize option will not affect the size of the oplog.

See Oplog Size for more information.

--replIndexPrefetch

Default: all

Storage Engine Specific Feature

--replIndexPrefetch is only available with the mmapv1 storage engine.

Determines which indexes secondary members of a replica set load into memory before applying operations from the oplog. By default secondaries load all indexes related to an operation into memory before applying operations from the oplog.

Set this option to one of the following:

Value Description
none Secondaries do not load indexes into memory.
all Secondaries load all indexes related to an operation.
_id_only Secondaries load no additional indexes into memory beyond the already existing _id index.
--enableMajorityReadConcern

New in version 3.2.

Enables read concern level of "majority". By default, "majority" level is not enabled.

Master-Slave Replication

These options provide access to conventional master-slave database replication. While this functionality remains accessible in MongoDB, replica sets are the preferred configuration for database replication.

Deprecated since version 3.2: MongoDB 3.2 deprecates the use of master-slave replication for components of sharded clusters.

--master

Configures the mongod to run as a replication master.

--slave

Configures the mongod to run as a replication slave.

--source <host><:port>

For use with the --slave option, the --source option designates the server that this instance will replicate.

--only <arg>

For use with the --slave option, the --only option specifies only a single database to replicate.

--slavedelay <value>

For use with the --slave option, the --slavedelay option configures a “delay” in seconds, for this slave to wait to apply operations from the master node.

--autoresync

For use with the --slave option. When set, the --autoresync option allows this slave to automatically resync if it is more than 10 seconds behind the master. This setting may be problematic if the --oplogSize specifies a too small oplog.

If the oplog is not large enough to store the difference in changes between the master’s current state and the state of the slave, this instance will forcibly resync itself unnecessarily. If you don’t specify --autoresync, the slave will not attempt an automatic resync more than once in a ten minute period.

--fastsync

In the context of replica set replication, set this option if you have seeded this member with an up-to-date copy of the entire dbPath of another member of the set. Otherwise the mongod will attempt to perform an initial sync, as though the member were a new member.

Warning

If the data is not perfectly synchronized and the mongod starts with fastsync, then the secondary or slave will be permanently out of sync with the primary, which may cause significant consistency problems.

Sharded Cluster Options

--configsvr

Required if starting a config server.

Declares that this mongod instance serves as the config server of a sharded cluster. When running with this option, clients (i.e. other cluster components) will not be able to write data to any database other than config and admin. The default port for a mongod with this option is 27019 and the default --dbpath directory is /data/configdb, unless specified.

Important

Starting in 3.4, you must deploy config servers as a replica set. The use of the deprecated mirrored mongod instances as config servers (SCCC) is no longer supported. To convert your config servers from SCCC to CSRS, see Upgrade Config Servers to Replica Set.

The replica set config servers (CSRS) must run the WiredTiger storage engine.

The --configsvr option creates a local oplog.

Do not use the --configsvr option with --shardsvr. Config servers cannot be a shard server.

--configsvrMode <string>

Available in MongoDB 3.2 version only

If set to sccc, indicates that the config servers are deployed as three mirrored mongod instances, even if one or more config servers is also a member of a replica set. configsvrMode only accepts the value sccc.

If unset, config servers running as replica sets expect to use the “config server replica set” protocol for writing to config servers, rather than the “mirrored mongod” write protocol.

--shardsvr

Required if starting a shard server.

Configures this mongod instance as a shard in a sharded cluster. The default port for these instances is 27018. The only effect of --shardsvr is to change the port number.

--moveParanoia

If specified, during chunk migration, a shard saves, to the moveChunk directory of the --dbpath, all documents migrated from that shard.

MongoDB does not automatically delete the data saved in the moveChunk directory.

--noMoveParanoia

Changed in version 3.2: Starting in 3.2, MongoDB uses --noMoveParanoia as the default.

During chunk migration, a shard does not save documents migrated from the shard.

TLS/SSL Options

See

Configure mongod and mongos for TLS/SSL for full documentation of MongoDB’s support.

--sslOnNormalPorts

Deprecated since version 2.6.

Enables TLS/SSL for mongod.

With --sslOnNormalPorts, a mongod requires TLS/SSL encryption for all connections on the default MongoDB port, or the port specified by --port. By default, --sslOnNormalPorts is disabled.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslMode <mode>

New in version 2.6.

Enables TLS/SSL or mixed TLS/SSL used for all network connections. The argument to the --sslMode option can be one of the following:

Value Description
disabled The server does not use TLS/SSL.
allowSSL Connections between servers do not use TLS/SSL. For incoming connections, the server accepts both TLS/SSL and non-TLS/non-SSL.
preferSSL Connections between servers use TLS/SSL. For incoming connections, the server accepts both TLS/SSL and non-TLS/non-SSL.
requireSSL The server uses and accepts only TLS/SSL encrypted connections.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslPEMKeyFile <filename>

Specifies the .pem file that contains both the TLS/SSL certificate and key. Specify the file name of the .pem file using relative or absolute paths.

You must specify --sslPEMKeyFile when TLS/SSL is enabled.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslPEMKeyPassword <value>

Specifies the password to de-crypt the certificate-key file (i.e. --sslPEMKeyFile). Use the --sslPEMKeyPassword option only if the certificate-key file is encrypted. In all cases, the mongod will redact the password from all logging and reporting output.

Changed in version 2.6: If the private key in the PEM file is encrypted and you do not specify the --sslPEMKeyPassword option, the mongod will prompt for a passphrase. See SSL Certificate Passphrase.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--clusterAuthMode <option>

Default: keyFile

New in version 2.6.

The authentication mode used for cluster authentication. If you use internal x.509 authentication, specify so here. This option can have one of the following values:

Value Description
keyFile Use a keyfile for authentication. Accept only keyfiles.
sendKeyFile For rolling upgrade purposes. Send a keyfile for authentication but can accept both keyfiles and x.509 certificates.
sendX509 For rolling upgrade purposes. Send the x.509 certificate for authentication but can accept both keyfiles and x.509 certificates.
x509 Recommended. Send the x.509 certificate for authentication and accept only x.509 certificates.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslClusterFile <filename>

New in version 2.6.

Specifies the .pem file that contains the x.509 certificate-key file for membership authentication for the cluster or replica set.

If --sslClusterFile does not specify the .pem file for internal cluster authentication, the cluster uses the .pem file specified in the --sslPEMKeyFile option.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslClusterPassword <value>

New in version 2.6.

Specifies the password to de-crypt the x.509 certificate-key file specified with --sslClusterFile. Use the --sslClusterPassword option only if the certificate-key file is encrypted. In all cases, the mongod will redact the password from all logging and reporting output.

If the x.509 key file is encrypted and you do not specify the --sslClusterPassword option, the mongod will prompt for a passphrase. See SSL Certificate Passphrase.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslCAFile <filename>

New in version 2.4.

Specifies the .pem file that contains the root certificate chain from the Certificate Authority. Specify the file name of the .pem file using relative or absolute paths.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

Warning

If the --sslCAFile option and its target file are not specified, x.509 client and member authentication will not function. mongod, and mongos in sharded systems, will not be able to verify the certificates of processes connecting to it against the trusted certificate authority (CA) that issued them, breaking the certificate chain.

As of version 2.6.4, mongod will not start with x.509 authentication enabled if the CA file is not specified.

--sslCRLFile <filename>

New in version 2.4.

Specifies the the .pem file that contains the Certificate Revocation List. Specify the file name of the .pem file using relative or absolute paths.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslAllowInvalidCertificates

New in version 2.6.

Bypasses the validation checks for TLS/SSL certificates on other servers in the cluster and allows the use of invalid certificates.

When using the --sslAllowInvalidCertificates setting, MongoDB logs a warning regarding the use of the invalid certificate.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslAllowInvalidHostnames

New in version 3.0.

Disables the validation of the hostnames in TLS/SSL certificates, when connecting to other mongod instances for inter-process authentication. This allows mongod to connect to other mongod instances if the hostnames in their certificates do not match their configured hostname.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslAllowConnectionsWithoutCertificates

New in version 2.4.

Changed in version 3.0.0: --sslWeakCertificateValidation became --sslAllowConnectionsWithoutCertificates. For compatibility, MongoDB processes continue to accept --sslWeakCertificateValidation, but all users should update their configuration files.

Disables the requirement for TLS/SSL certificate validation that --sslCAFile enables. With the --sslAllowConnectionsWithoutCertificates option, the mongod will accept connections when the client does not present a certificate when establishing the connection.

If the client presents a certificate and the mongod has --sslAllowConnectionsWithoutCertificates enabled, the mongod will validate the certificate using the root certificate chain specified by --sslCAFile and reject clients with invalid certificates.

Use the --sslAllowConnectionsWithoutCertificates option if you have a mixed deployment that includes clients that do not or cannot present certificates to the mongod.

Changed in version 3.0: Most MongoDB distributions now include support for TLS/SSL. See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients for more information about TLS/SSL and MongoDB.

--sslDisabledProtocols <protocol(s)>

New in version 3.0.7.

Prevents a MongoDB server running with SSL from accepting incoming connections that use a specific protocol or protocols. --sslDisabledProtocols recognizes the following protocols: TLS1_0, TLS1_1, and TLS1_2. Specifying an unrecognized protocol will prevent the server from starting.

To specify multiple protocols, use a comma separated list of protocols.

Members of replica sets and sharded clusters must speak at least one protocol in common.

--sslFIPSMode

New in version 2.4.

Directs the mongod to use the FIPS mode of the installed OpenSSL library. Your system must have a FIPS compliant OpenSSL library to use the --sslFIPSMode option.

Note

FIPS-compatible SSL is available only in MongoDB Enterprise. See Configure MongoDB for FIPS for more information.

Audit Options

--auditDestination

New in version 2.6.

Enables auditing and specifies where mongod sends all audit events.

--auditDestination can have one of the following values:

Value Description
syslog

Output the audit events to syslog in JSON format. Not available on Windows. Audit messages have a syslog severity level of info and a facility level of user.

The syslog message limit can result in the truncation of audit messages. The auditing system will neither detect the truncation nor error upon its occurrence.

console Output the audit events to stdout in JSON format.
file Output the audit events to the file specified in --auditPath in the format specified in --auditFormat.

Note

Available only in MongoDB Enterprise.

--auditFormat

New in version 2.6.

Specifies the format of the output file for auditing if --auditDestination is file. The --auditFormat option can have one of the following values:

Value Description
JSON Output the audit events in JSON format to the file specified in --auditPath.
BSON Output the audit events in BSON binary format to the file specified in --auditPath.

Printing audit events to a file in JSON format degrades server performance more than printing to a file in BSON format.

Note

Available only in MongoDB Enterprise.

--auditPath

New in version 2.6.

Specifies the output file for auditing if --auditDestination has value of file. The --auditPath option can take either a full path name or a relative path name.

Note

Available only in MongoDB Enterprise.

--auditFilter

New in version 2.6.

Specifies the filter to limit the types of operations the audit system records. The option takes a string representation of a query document of the form:

{ <field1>: <expression1>, ... }

The <field> can be any field in the audit message, including fields returned in the param document. The <expression> is a query condition expression.

To specify an audit filter, enclose the filter document in single quotes to pass the document as a string.

To specify the audit filter in a configuration file, you must use the YAML format of the configuration file.

Note

Available only in MongoDB Enterprise.

SNMP Options

--snmp-subagent

Runs SNMP as a subagent. For more information, see Monitor MongoDB With SNMP on Linux.

--snmp-master

Runs SNMP as a master. For more information, see Monitor MongoDB With SNMP on Linux.

inMemory Options

--inMemorySizeGB <float>

Default: 50% of physical RAM less 1 GB

Changed in version 3.4: Values can range from 256MB to 10TB and can be a float.

Maximum amount of memory to allocate for in-memory storage engine data, including indexes, oplog if the mongod is part of replica set, replica set or sharded cluster metadata, etc.

By default, the in-memory storage engine uses 50% of physical RAM minus 1 GB.

Enterprise Feature

Available in MongoDB Enterprise only.

Encryption Key Management Options

--enableEncryption <boolean>

Default: False

New in version 3.2.

Enables encryption for the WiredTiger storage engine. You must set to true to pass in encryption keys and configurations.

Enterprise Feature

Available in MongoDB Enterprise only.

--encryptionCipherMode <string>

Default: AES256-CBC

New in version 3.2.

The cipher mode to use for encryption at rest:

Mode Description
AES256-CBC 256-bit Advanced Encryption Standard in Cipher Block Chaining Mode
AES256-GCM 256-bit Advanced Encryption Standard in Galois/Counter Mode

Enterprise Feature

Available in MongoDB Enterprise only.

--encryptionKeyFile <string>

New in version 3.2.

The path to the local keyfile when managing keys via process other than KMIP. Only set when managing keys via process other than KMIP. If data is already encrypted using KMIP, MongoDB will throw an error.

Requires enableEncryption to be true.

Enterprise Feature

Available in MongoDB Enterprise only.

--kmipKeyIdentifier <string>

New in version 3.2.

Unique KMIP identifier for an existing key within the KMIP server. Include to use the key associated with the identifier as the system key. You can only use the setting the first time you enable encryption for the mongod instance. Requires enableEncryption to be true.

If unspecified, MongoDB will request that the KMIP server create a new key to utilize as the system key.

If the KMIP server cannot locate a key with the specified identifier or the data is already encrypted with a key, MongoDB will throw an error

Enterprise Feature

Available in MongoDB Enterprise only.

--kmipRotateMasterKey <boolean>

Default: False

New in version 3.2.

If true, rotate the master key and re-encrypt the internal keystore.

Enterprise Feature

Available in MongoDB Enterprise only.

--kmipServerName <string>

New in version 3.2.

Hostname or IP address of key management solution running a KMIP server. Requires enableEncryption to be true.

Enterprise Feature

Available in MongoDB Enterprise only.

--kmipPort <number>

Default: 5696

New in version 3.2.

Port number the KMIP server is listening on. Requires that a kmipServerName be provided. Requires enableEncryption to be true.

Enterprise Feature

Available in MongoDB Enterprise only.

--kmipClientCertificateFile <string>

New in version 3.2.

String containing the path to the client certificate used for authenticating MongoDB to the KMIP server. Requires that a kmipServerName be provided.

Enterprise Feature

Available in MongoDB Enterprise only.

--kmipClientCertificatePassword <string>

New in version 3.2.

The password (if one exists) for the client certificate passed into kmipClientCertificateFile. Is used for authenticating MongoDB to the KMIP server. Requires that a kmipClientCertificateFile be provided.

Enterprise Feature

Available in MongoDB Enterprise only.

--kmipServerCAFile <string>

New in version 3.2.

Path to CA File. Used for validating secure client connection to KMIP server.

Text Search Options

--basisTechRootDirectory <path>

New in version 3.2.

Specify the root directory of the Basis Technology Rosette Linguistics Platform installation to support additional languages for text search operations.

Enterprise Feature

Available in MongoDB Enterprise only.