`mongos` Instances

Synopsis

For a sharded cluster, the mongos instances provide the interface between the client applications and the sharded cluster. The mongos instances route queries and write operations to the shards. From the perspective of the application, a mongos instance behaves identically to any other MongoDB instance.

Considerations

Never change the name of the mongos binary.
MongoDB disables support for TLS 1.0 and TLS 1.1 encryption on systems where TLS 1.2+ is available.
The mongos binary cannot connect to mongod instances whose feature compatibility version (FCV) is greater than that of the mongos. For example, you cannot connect a MongoDB 6.0 version mongos to a 8.0 sharded cluster with FCV set to 8.0. You can, however, connect a MongoDB 6.0 version mongos to a 8.0 sharded cluster with FCV set to 6.0.
mongod includes a Full Time Diagnostic Data Capture mechanism to assist MongoDB engineers with troubleshooting deployments. If this thread fails, it terminates the originating process. To avoid the most common failures, confirm that the user running the process has permissions to create the FTDC diagnostic.data directory. For mongod the directory is within systemLog.path.

Options

Tip

Self-Managed Configuration File Settings and Command-Line Options Mapping

Note

MongoDB deprecates the SSL options and instead adds new corresponding TLS options.
MongoDB adds --tlsClusterCAFile/net.tls.clusterCAFile.

Note

MongoDB 5.0 removes the --serviceExecutor command-line option and the corresponding net.serviceExecutor configuration option.

Core Options

--help, -h: Returns information on the options and use of mongos.

--version: Returns the mongos 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 mongos. The options are equivalent to the command-line configuration options. See Self-Managed Configuration File Options for more information.

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

--configExpand <none|rest|exec>

Default: none

Enables using Expansion Directives in configuration files. Expansion directives allow you to set externally sourced values for configuration file options.

--configExpand supports the following expansion directives:

Value	Description
`none`	Default. `mongos` does not expand expansion directives. `mongos` fails to start if any configuration file settings use expansion directives.
`rest`	`mongos` expands `__rest` expansion directives when parsing the configuration file.
`exec`	`mongos` expands `__exec` expansion directives when parsing the configuration file.

You can specify multiple expansion directives as a comma-separated list, for example: rest, exec. If the configuration file contains expansion directives not specified to --configExpand, the mongos returns an error and terminates.

See External Configuration Values for Self-Managed MongoDB for configuration files for more information on expansion directives.

--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, for example: -vvvvv.

--quiet

Runs mongos 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

The TCP port on which the mongos instance listens for client connections.

The --port option accepts a range of values between 0 and 65535. Setting the port to 0 configures mongos to use an arbitrary port assigned by the operating system.

--bind_ip <hostnames|ipaddresses|Unix domain socket paths>

Default: localhost

The hostnames and/or IP addresses and/or full Unix domain socket paths on which mongos should listen for client connections. You may attach mongos to any interface. To bind to multiple addresses, enter a list of comma-separated values.

Example

localhost,/tmp/mongod.sock

You can specify both IPv4 and IPv6 addresses, or hostnames that resolve to an IPv4 or IPv6 address.

Example

localhost, 2001:0DB8:e132:ba26:0d5c:2774:e7f9:d513

Note

If specifying an IPv6 address or a hostname that resolves to an IPv6 address to --bind_ip, you must start mongos with --ipv6 to enable IPv6 support. Specifying an IPv6 address to --bind_ip does not enable IPv6 support.

If specifying a link-local IPv6 address (fe80::/10), you must append the zone index to that address (i.e. fe80::<address>%<adapter-name>).

Example

localhost,fe80::a00:27ff:fee0:1fcf%enp0s3

Important

To avoid configuration updates due to IP address changes, use DNS hostnames instead of IP addresses. It is particularly important to use a DNS hostname instead of an IP address when configuring replica set members or sharded cluster members.

Use hostnames instead of IP addresses to configure clusters across a split network horizon. Starting in MongoDB 5.0, nodes that are only configured with an IP address fail startup validation and do not start.

Warning

Before you bind your instance to a publicly-accessible IP address, you must secure your cluster from unauthorized access. For a complete list of security recommendations, see Security Checklist for Self-Managed Deployments. At minimum, consider enabling authentication and hardening network infrastructure.

For more information about IP Binding, refer to the IP Binding in Self-Managed Deployments documentation.

To bind to all IPv4 addresses, enter 0.0.0.0.

To bind to all IPv4 and IPv6 addresses, enter ::,0.0.0.0 or an asterisk "*" (enclose the asterisk in quotes to avoid filename pattern expansion). Alternatively, use the net.bindIpAll setting.

Note

--bind_ip and --bind_ip_all are mutually exclusive. Specifying both options causes mongos to throw an error and terminate.
The command-line option --bind overrides the configuration file setting net.bindIp.

--bind_ip_all

If specified, the mongos instance binds to all IPv4 addresses (i.e. 0.0.0.0). If mongos starts with --ipv6, --bind_ip_all also binds to all IPv6 addresses (i.e. ::).

mongos only supports IPv6 if started with --ipv6. Specifying --bind_ip_all alone does not enable IPv6 support.

Warning

For more information about IP Binding, refer to the IP Binding in Self-Managed Deployments documentation.

Alternatively, you can set the --bind_ip option to ::,0.0.0.0 or to an asterisk "*" (enclose the asterisk in quotes to avoid filename pattern expansion).

Note

--bind_ip and --bind_ip_all are mutually exclusive. That is, you can specify one or the other, but not both.

--listenBacklog <number>

Default: Target system SOMAXCONN constant

The maximum number of connections that can exist in the listen queue.

Warning

Consult your local system's documentation to understand the limitations and configuration requirements before using this parameter.

Important

To prevent undefined behavior, specify a value for this parameter between 1 and the local system SOMAXCONN constant.

The default value for the listenBacklog parameter depends on the target system. On Linux, MongoDB uses /proc/sys/net/core/somaxconn. On all other target systems, MongoDB uses the compile time constant SOMAXCONN.

Some systems may interpret SOMAXCONN symbolically, and others numerically. The actual listen backlog applied in practice may differ from any numeric interpretation of the SOMAXCONN constant or argument to --listenBacklog.

Passing a value for the listenBacklog parameter that exceeds the SOMAXCONN constant for the local system is, by the letter of the standards, undefined behavior. Higher values may be silently integer truncated, may be ignored, may cause unexpected resource consumption, or have other adverse consequences.

--maxConns <number>

The maximum number of simultaneous connections that mongos accepts. 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.

This is particularly useful for a mongos if you have a client that creates multiple connections and allows them to timeout rather than closing them.

In this case, set maxIncomingConnections to a value slightly higher than the maximum number of connections that the client creates, or the maximum size of the connection pool.

This setting prevents the mongos from causing connection spikes on the individual shards. Spikes like these may disrupt the operation and memory allocation of the sharded cluster.

--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 (--logpath).

The --syslog option is not supported on Windows.

Warning

The syslog daemon generates timestamps when it logs a message, not when MongoDB issues the message. This can lead to misleading timestamps for log entries, especially when the system is under heavy load. We recommend using the --logpath option for production systems to ensure accurate timestamps.

MongoDB includes the component in its log messages to syslog.

...  ACCESS   [repl writer worker 5] Unsupported modification to roles collection ...

--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 mongos instance restarts. Without this option, mongod will back up the existing log and create a new file.

--logRotate <string>

Default: rename

Determines the behavior for the logRotate command when rotating the server log and/or the audit log. 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.

--redactClientLogData

Available in MongoDB Enterprise only.

A mongos running with --redactClientLogData redacts any message accompanying a given log event before logging. This prevents the mongos 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 at Rest and TLS/SSL (Transport Encryption) to assist compliance with regulatory requirements.

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

Diagnostics on a mongos 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.

On a running mongos, use setParameter with the redactClientLogData parameter to configure this setting.

--timeStampFormat <string>

Default: iso8601-local

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

Value	Description
`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: `1969-12-31T19:00:00.000-05:00`

Note

--timeStampFormat no longer supports ctime. An example of ctime formatted date is: Wed Dec 31 18:17:54.811.

--pidfilepath <path>: Specifies a file location to store the process ID (PID) of the mongos process. The user running the mongod or mongos process must be able to write to this path. If the --pidfilepath option is not specified, the process does not create a PID file. This option is generally only useful in combination with the --fork option.
Note
Linux
On Linux, PID file management is generally the responsibility of your distro's init system: usually a service file in the /etc/init.d directory, or a systemd unit file registered with systemctl. Only use the --pidfilepath option if you are not using one of these init systems. For more information, please see the respective Installation Guide for your operating system.
Note
macOS
On macOS, PID file management is generally handled by brew. Only use the --pidfilepath option if you are not using brew on your macOS system. For more information, please see the respective Installation Guide for your operating system.

--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 client authorization. See Self-Managed Internal/Membership Authentication for more information.

Keyfiles for internal membership authentication use YAML format to allow for multiple keys in a keyfile. The YAML format accepts either:

A single key string (same as in earlier versions)
A sequence of key strings

The YAML format is compatible with the existing single-key keyfiles that use the text file format.

--setParameter <options>: Specifies one of the MongoDB parameters described in MongoDB Server Parameters for a Self-Managed Deployment. You can specify multiple setParameter fields.

--noscripting

Disables the scripting engine. When disabled, you cannot use operations that perform server-side execution of JavaScript code, such as the $where query operator, mapReduce command, $accumulator, and $function.

If you do not use these operations, disable server-side scripting.

--nounixsocket

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

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

--nounixsocket is set
net.bindIp does not specify localhost or its associated IP address

mongos installed from official Install MongoDB Community Edition on Debian and Install MongoDB Community Edition on Red Hat or CentOS 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 mongos process creates a socket with /tmp as a prefix. MongoDB creates and listens on a UNIX socket unless one of the following is true:

net.bindIp does not specify localhost or its associated IP address

--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 mongos process in the background. The --fork option is not supported on Windows.

By default mongos does not run as a daemon. You run mongos as a daemon by using either --fork or a controlling process that handles daemonization, such as upstart or systemd.

Using the --fork option requires that you configure log output for the mongos with one of the following:

--logpath
--syslog

--transitionToAuth

Allows the mongos 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 mongos creates an authenticated connection with any mongod or mongos in the deployment using a matching keyfile. If the security mechanisms do not match, the mongos utilizes a non-authenticated connection instead.

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

--networkMessageCompressors <string>

Default: snappy,zstd,zlib

Specifies the default compressor(s) to use for communication between this mongos instance and:

other members of the sharded cluster
mongosh
drivers that support the OP_COMPRESSED message format.

MongoDB supports the following compressors:

Both mongod and mongos instances default to snappy,zstd,zlib compressors, in that order.

To disable network compression, set the value to disabled.

Important

Messages are compressed when both parties enable network compression. Otherwise, messages between the parties are uncompressed.

If you specify multiple compressors, then the order in which you list the compressors matter as well as the communication initiator. For example, if mongosh specifies the following network compressors zlib,snappy and the mongod specifies snappy,zlib, messages between mongosh and mongod uses zlib.

If the parties do not share at least one common compressor, messages between the parties are uncompressed. For example, if mongosh specifies the network compressor zlib and mongod specifies snappy, messages between mongosh and mongod are not compressed.

--timeZoneInfo <path>

The full path from which to load the time zone database. If this option is not provided, then MongoDB uses its built-in time zone database.

The configuration file included with Linux and macOS packages sets the time zone database path to /usr/share/zoneinfo by default.

The built-in time zone database is a copy of the Olson/IANA time zone database. It is updated along with MongoDB releases, but the time zone database release cycle differs from the MongoDB release cycle. The most recent release of the time zone database is available on our timelib library to provide accurate conversions between timezones. Due to a recent update, timelib could create inaccurate time zone conversions in older versions of MongoDB.

To explicitly link to the time zone database in versions of MongoDB prior to 5.0, download the time zone database. and use the timeZoneInfo parameter.

--outputConfig

Outputs the mongos instance's configuration options, formatted in YAML, to stdout and exits the mongos instance. For configuration options that uses External Configuration Values for Self-Managed MongoDB, --outputConfig returns the resolved value for those options.

Warning

This may include any configured passwords or secrets previously obfuscated through the external source.

For usage examples, see:

Sharded Cluster Options

--configdb <replicasetName>/<config1>,<config2>...

Specifies the configuration servers for the sharded cluster.

Config servers for sharded clusters are deployed as a replica set. The replica set config servers must run the WiredTiger storage engine.

Specify the config server replica set name and the hostname and port of at least one of the members of the config server replica set.

sharding:
  configDB: <configReplSetName>/cfg1.example.net:27019, cfg2.example.net:27019,...

The mongos instances for the sharded cluster must specify the same config server replica set name but can specify hostname and port of different members of the replica set.

--localThreshold

Default: 15

Specifies the ping time, in milliseconds, that mongos uses to determine which secondary replica set members to pass read operations from clients. The default value of 15 corresponds to the default value in all of the client drivers.

When mongos receives a request that permits reads to secondary members, it:

Finds the member of the set with the lowest ping time.
Constructs a list of replica set members that is within a ping time of 15 milliseconds of the nearest suitable member of the set.
If you specify a value for the --localThreshold option, mongos constructs the list of replica members that are within the latency allowed by this value.
Selects a member to read from at random from this list.

The ping time used for a member compared by the --localThreshold setting is a moving average of recent ping times, calculated at most every 10 seconds. As a result, some queries may reach members above the threshold until the mongos recalculates the average.

See the Read Preference for Replica Sets section of the read preference documentation for more information.

TLS Options

Tip

See:

Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments for full documentation of MongoDB's support.

--tlsMode <mode>

Enables TLS used for all network connections. The argument to the --tlsMode option can be one of the following:

Value	Description
`disabled`	The server does not use TLS.
`allowTLS`	Connections between servers do not use TLS. For incoming connections, the server accepts both TLS and non-TLS.
`preferTLS`	Connections between servers use TLS. For incoming connections, the server accepts both TLS and non-TLS.
`requireTLS`	The server uses and accepts only TLS encrypted connections.

If --tlsCAFile or tls.CAFile is not specified and you are not using X.509 authentication, you must set the tlsUseSystemCA parameter to true. This makes MongoDB use the system-wide CA certificate store when connecting to a TLS-enabled server.

If using X.509 authentication, --tlsCAFile or tls.CAFile must be specified unless using --tlsCertificateSelector.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsCertificateKeyFile <filename>

Note

On macOS or Windows, you can use a certificate from the operating system's secure store instead of specifying a PEM file. See --tlsCertificateSelector.

Specifies the .pem file that contains both the TLS certificate and key.

On Linux/BSD, you must specify --tlsCertificateKeyFile when TLS is enabled.
On Windows or macOS, you must specify either --tlsCertificateKeyFile or --tlsCertificateSelector when TLS is enabled.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsCertificateKeyFilePassword <value>

Specifies the password to decrypt the certificate-key file (i.e. --tlsCertificateKeyFile). Use the --tlsCertificateKeyFilePassword option only if the certificate-key file is encrypted. In all cases, the mongos redacts the password from all logging and reporting output.

On Linux/BSD, if the private key in the PEM file is encrypted and you do not specify the --tlsCertificateKeyFilePassword option, MongoDB prompts for a passphrase. See TLS/SSL Certificate Passphrase.
On macOS or Windows, if the private key in the PEM file is encrypted, you must explicitly specify the --tlsCertificateKeyFilePassword option. Alternatively, you can use a certificate from the secure system store (see --tlsCertificateSelector) instead of a PEM file or use an unencrypted PEM file.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--clusterAuthMode <option>

Default: keyFile

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.

If using X.509 authentication, --tlsCAFile or tls.CAFile must be specified unless using --tlsCertificateSelector.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsClusterFile <filename>

Note

On macOS or Windows, you can use a certificate from the operating system's secure store instead of a PEM file. See --tlsClusterCertificateSelector.

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

If --tlsClusterFile does not specify the .pem file for internal cluster authentication or the alternative --tlsClusterCertificateSelector, the cluster uses the .pem file specified in the --tlsCertificateKeyFile option or the certificate returned by the --tlsCertificateSelector.

If using X.509 authentication, --tlsCAFile or tls.CAFile must be specified unless using --tlsCertificateSelector.

mongod / mongos logs a warning on connection if the presented X.509 certificate expires within 30 days of the mongod/mongos host system time.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsClusterPassword <value>

Specifies the password to decrypt the X.509 certificate-key file specified with --tlsClusterFile. Use the --tlsClusterPassword option only if the certificate-key file is encrypted. In all cases, the mongos redacts the password from all logging and reporting output.

On Linux/BSD, if the private key in the X.509 file is encrypted and you do not specify the --tlsClusterPassword option, MongoDB prompts for a passphrase. See TLS/SSL Certificate Passphrase.
On macOS or Windows, if the private key in the X.509 file is encrypted, you must explicitly specify the --tlsClusterPassword option. Alternatively, you can either use a certificate from the secure system store (see --tlsClusterCertificateSelector) instead of a cluster PEM file or use an unencrypted PEM file.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsCAFile <filename>

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.

On macOS or Windows, you can use a certificate from the operating system's secure store instead of a PEM key file. See --tlsCertificateSelector. When using the secure store, you do not need to, but can, also specify the --tlsCAFile.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsClusterCAFile <filename>

Specifies the .pem file that contains the root certificate chain from the Certificate Authority used to validate the certificate presented by a client establishing a connection. Specify the file name of the .pem file using relative or absolute paths.

If --tlsClusterCAFile does not specify the .pem file for validating the certificate from a client establishing a connection, the cluster uses the .pem file specified in the --tlsCAFile option.

--tlsClusterCAFile lets you use separate Certificate Authorities to verify the client to server and server to client portions of the TLS handshake.

On macOS or Windows, you can use a certificate from the operating system's secure store instead of a PEM key file. See --tlsClusterCertificateSelector. When using the secure store, you do not need to, but can, also specify the --tlsClusterCAFile.

Requires that --tlsCAFile is set.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsCertificateSelector <parameter>=<value>

Note

Available on Windows and macOS as an alternative to --tlsCertificateKeyFile.

The --tlsCertificateKeyFile and --tlsCertificateSelector options are mutually exclusive. You can only specify one.

Specifies a certificate property in order to select a matching certificate from the operating system's certificate store.

--tlsCertificateSelector accepts an argument of the format <property>=<value> where the property can be one of the following:

Property	Value type	Description
`subject`	ASCII string	Subject name or common name on certificate
`thumbprint`	hex string	A sequence of bytes, expressed as hexadecimal, used to identify a public key by its SHA-1 digest. The `thumbprint` is sometimes referred to as a `fingerprint`.

When using the system SSL certificate store, OCSP (Online Certificate Status Protocol) is used to validate the revocation status of certificates.

Note

You cannot use the rotateCertificates command or the db.rotateCertificates() shell method when using net.tls.certificateSelector or --tlsCertificateSelector set to thumbprint

--tlsClusterCertificateSelector <parameter>=<value>

Note

Available on Windows and macOS as an alternative to --tlsClusterFile.

--tlsClusterFile and --tlsClusterCertificateSelector options are mutually exclusive. You can only specify one.

Specifies a certificate property in order to select a matching certificate from the operating system's certificate store to use for internal authentication.

--tlsClusterCertificateSelector accepts an argument of the format <property>=<value> where the property can be one of the following:

Property	Value type	Description
`subject`	ASCII string	Subject name or common name on certificate
`thumbprint`	hex string	A sequence of bytes, expressed as hexadecimal, used to identify a public key by its SHA-1 digest. The `thumbprint` is sometimes referred to as a `fingerprint`.

mongod / mongos logs a warning on connection if the presented X.509 certificate expires within 30 days of the mongod/mongos host system time.

--tlsCRLFile <filename>

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

Note

You cannot specify a CRL file on macOS. Instead, you can use the system SSL certificate store, which uses OCSP (Online Certificate Status Protocol) to validate the revocation status of certificates. To use the system SSL certificate store, see --tlsCertificateSelector.
To check for certificate revocation, MongoDB enables the use of OCSP (Online Certificate Status Protocol) by default as an alternative to specifying a CRL file or using the system SSL certificate store.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsAllowConnectionsWithoutCertificates

By default, the server bypasses client certificate validation unless the server is configured to use a CA file. If a CA file is provided, the following rules apply:

For clients that don't provide certificates, mongod or mongos encrypts the TLS/SSL connection, assuming the connection is successfully made.
For clients that present a certificate, mongos performs certificate validation using the root certificate chain specified by --tlsCAFile and reject clients with invalid certificates.

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

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsAllowInvalidCertificates

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

Note

If you specify --tlsAllowInvalidCertificates or tls.allowInvalidCertificates: true when using X.509 authentication, an invalid certificate is only sufficient to establish a TLS connection but is insufficient for authentication.

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

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsAllowInvalidHostnames

Disables the validation of the hostnames in TLS certificates, when connecting to other members of the replica set or sharded cluster for inter-process authentication. This allows mongos to connect to other members if the hostnames in their certificates do not match their configured hostname.

For more information about TLS and MongoDB, see Configure MongoDB Instances for TLS/SSL on Self-Managed Deployments and TLS/SSL Configuration for Clients .

--tlsDisabledProtocols <protocol(s)>

Prevents a MongoDB server running with TLS from accepting incoming connections that use a specific protocol or protocols. To specify multiple protocols, use a comma separated list of protocols.

--tlsDisabledProtocols recognizes the following protocols: TLS1_0, TLS1_1, TLS1_2, and TLS1_3.

On macOS, you cannot disable TLS1_1 and leave both TLS1_0 and TLS1_2 enabled. You must disable at least one of the other two, for example, TLS1_0,TLS1_1.
To list multiple protocols, specify as a comma separated list of protocols. For example TLS1_0,TLS1_1.
Specifying an unrecognized protocol prevents the server from starting.
The specified disabled protocols overrides any default disabled protocols.

MongoDB disables the use of TLS 1.0 if TLS 1.1+ is available on the system. To enable the disabled TLS 1.0, specify none to --tlsDisabledProtocols.

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

Tip

Disallow Protocols

--tlsFIPSMode: Directs the mongos to use the FIPS mode of the TLS library. Your system must have a FIPS compliant library to use the --tlsFIPSMode option.
Note
FIPS-compatible TLS/SSL is available only in MongoDB Enterprise. See Configure MongoDB for FIPS for more information.

Audit Options

--auditCompressionMode

New in version 5.3.

Specifies the compression mode for audit log encryption. You must also enable audit log encryption using either --auditEncryptionKeyUID or --auditLocalKeyFile.

--auditCompressionMode can be set to one of these values:

Value	Description
`zstd`	Use the zstd algorithm to compress the audit log.
`none` (default)	Do not compress the audit log.

Note

Available only in MongoDB Enterprise. MongoDB Enterprise and Atlas have different configuration requirements.

--auditDestination

Enables auditing and specifies where mongos 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 neither detects the truncation nor errors 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 and MongoDB Atlas.

--auditEncryptionKeyUID

New in version 6.0.

Specifies the unique identifier of the Key Management Interoperability Protocol (KMIP) key for audit log encryption.

You cannot use --auditEncryptionKeyUID and --auditLocalKeyFile together.

Note

Available only in MongoDB Enterprise. MongoDB Enterprise and Atlas have different configuration requirements.

--auditFormat

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 and MongoDB Atlas.

--auditLocalKeyFile

New in version 5.3.

Specifies the path and file name for a local audit key file for audit log encryption.

Note

Only use --auditLocalKeyFile for testing because the key is not secured. To secure the key, use --auditEncryptionKeyUID and an external Key Management Interoperability Protocol (KMIP) server.

You cannot use --auditLocalKeyFile and --auditEncryptionKeyUID together.

Note

Available only in MongoDB Enterprise. MongoDB Enterprise and Atlas have different configuration requirements.

--auditPath: 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 and MongoDB Atlas.

--auditFilter

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 and MongoDB Atlas.

--auditSchema

Type: string

Default: mongo

New in version 8.0.

Specifies the format used for audit logs. You can specify one of the following values for --auditSchema:

Value	Description
`mongo`	Logs are written in a format designed by MongoDB. For example log messages, see mongo Schema Audit Messages.
`OCSF`	Logs are written in OCSF format. This option provides logs in a standardized format compatible with log processors. For example log messages, see OCSF Schema Audit Messages.

Profiler Options

--slowms <integer>

Default: 100

The slow operation time threshold, in milliseconds. Operations that run for longer than this threshold are considered slow.

When logLevel is set to 0, MongoDB records slow operations to the diagnostic log at a rate determined by slowOpSampleRate.

At higher logLevel settings, all operations appear in the diagnostic log regardless of their latency.

For mongos instances, affects the diagnostic log only and not the profiler since profiling is not available on mongos.

--slowOpSampleRate <double>

Default: 1.0

The fraction of slow operations that should be logged. --slowOpSampleRate accepts values between 0 and 1, inclusive.

For mongos instances, --slowOpSampleRate affects the diagnostic log only and not the profiler since profiling is not available on mongos.

LDAP Authentication and Authorization Options

Note

Starting in MongoDB 8.0, LDAP authentication and authorization is deprecated. LDAP is available and will continue to operate without changes throughout the lifetime of MongoDB 8. LDAP will be removed in a future major release.

For details, see LDAP Deprecation.

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

Available in MongoDB Enterprise only.

The LDAP server against which the mongos authenticates users or determines what actions a user is authorized to perform on a given database. If the LDAP server specified has any replicated instances, you may specify the host and port of each replicated server in a comma-delimited list.

If your LDAP infrastructure partitions the LDAP directory over multiple LDAP servers, specify one LDAP server or any of its replicated instances to --ldapServers. MongoDB supports following LDAP referrals as defined in RFC 4511 4.1.10. Do not use --ldapServers for listing every LDAP server in your infrastructure.

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

If unset, mongos cannot use LDAP authentication or authorization.

--ldapValidateLDAPServerConfig <boolean>

Available in MongoDB Enterprise

A flag that determines if the mongos instance checks the availability of the LDAP server(s) as part of its startup:

If true, the mongos instance performs the availability check and only continues to start up if the LDAP server is available.
If false, the mongos instance skips the availability check; i.e. the instance starts up even if the LDAP server is unavailable.

--ldapQueryUser <string>

Available in MongoDB Enterprise only.

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

Only required if any of the following are true:

Using LDAP authorization.
Using an LDAP query for username transformation.
The LDAP server disallows anonymous binds

You must use --ldapQueryUser with --ldapQueryPassword.

If unset, mongos doesn't attempt to bind to the LDAP server.

This setting can be configured on a running mongos 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>

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, mongos doesn't attempt to bind to the LDAP server.

This setting can be configured on a running mongos 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

Available in MongoDB Enterprise for the Windows platform only.

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

Only required if:

Using LDAP authorization.
Using an LDAP query for username transformation.
The LDAP server disallows anonymous binds

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

--ldapBindMethod <string>

Default: simple

Available in MongoDB Enterprise only.

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

--ldapBindMethod supports the following values:

simple - mongos uses simple authentication.
sasl - mongos uses SASL protocol for authentication

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

--ldapBindSaslMechanisms <string>

Default: DIGEST-MD5

Available in MongoDB Enterprise only.

A comma-separated list of SASL mechanisms mongos can use when authenticating to the LDAP server. The mongos and the LDAP server must agree on at least one mechanism. The mongos dynamically loads any SASL mechanism libraries installed on the host machine at runtime.

Install and configure the appropriate libraries for the selected SASL mechanism(s) on both the mongos host and the remote LDAP server host. Your operating system may include certain SASL libraries by default. Defer to the documentation associated with each SASL mechanism for guidance on installation and configuration.

If using the GSSAPI SASL mechanism for use with Kerberos Authentication on Self-Managed Deployments, verify the following for the mongos host machine:

Linux

The KRB5_CLIENT_KTNAME environment variable resolves to the name of the client Linux Keytab Files for the host machine. For more on Kerberos environment variables, please defer to the Kerberos documentation.
The client keytab includes a User Principal for the mongos to use when connecting to the LDAP server and execute LDAP queries.

Windows

If connecting to an Active Directory server, the Windows Kerberos configuration automatically generates a Ticket-Granting-Ticket when the user logs onto the system. Set --ldapBindWithOSDefaults to true to allow mongos to use the generated credentials when connecting to the Active Directory server and execute queries.

Set --ldapBindMethod to sasl to use this option.

Note

For a complete list of SASL mechanisms see the IANA listing. Defer to the documentation for your LDAP or Active Directory service for identifying the SASL mechanisms compatible with the service.

MongoDB is not a source of SASL mechanism libraries, nor is the MongoDB documentation a definitive source for installing or configuring any given SASL mechanism. For documentation and support, defer to the SASL mechanism library vendor or owner.

For more information on SASL, defer to the following resources:

For Linux, please see the Windows SASL documentation.

--ldapTransportSecurity <string>

Default: tls

Available in MongoDB Enterprise only.

By default, mongos 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 mongos and the LDAP server.

Warning

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

--ldapTimeoutMS <int>

Default: 10000

Available in MongoDB Enterprise only.

The amount of time in milliseconds mongos 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 mongos using setParameter.

--ldapRetryCount <int>

New in version 6.1.

Default: 0

Available in MongoDB Enterprise only.

Number of operation retries by the server LDAP manager after a network error.

--ldapUserToDNMapping <string>

Available in MongoDB Enterprise only.

Maps the username provided to mongos 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, such as x.509 or 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. The result of the substitution must be an RFC4514 escaped string.	`"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. `mongos` executes the query against the LDAP server to retrieve the LDAP DN for the authenticated user. `mongos` requires exactly one returned result for the transformation to be successful, or `mongos` skips this transformation.	`"ou=engineering,dc=example, dc=com??one?(user={0})"`

Note

An explanation of RFC4514, RFC4515, RFC4516, or LDAP queries is out of scope for the MongoDB Documentation. Please review the RFC directly or use your preferred LDAP resource.

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

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

mongos also returns an error if one of the transformations cannot be evaluated due to networking or authentication failures to the LDAP server. mongos rejects the connection request and does not check the remaining documents in the array.

Starting in MongoDB 5.0, --ldapUserToDNMapping accepts an empty string "" or empty array [ ] in place of a mapping documnent. If providing an empty string or empty array to --ldapUserToDNMapping, MongoDB maps the authenticated username as the LDAP DN. Previously, providing an empty mapping document would cause mapping to fail.

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 [email protected] 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 [email protected] 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)". mongos executes this query against the LDAP server, returning the result "cn=bob,ou=dba,dc=example,dc=com".

If --ldapUserToDNMapping is unset, mongos 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 mongos using the setParameter database command.

Additional Options

--ipv6

Enables IPv6 support. mongos disables IPv6 support by default.

Setting --ipv6 does not direct the mongos to listen on any local IPv6 addresses or interfaces. To configure the mongos to listen on an IPv6 interface, you must either:

Configure --bind_ip with one or more IPv6 addresses or hostnames that resolve to IPv6 addresses, or
Set --bind_ip_all to true.

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