MongoDB runs as a standard program. You can start MongoDB from a command line by issuing the mongod command and specifying options. For a list of options, see the mongod reference. MongoDB can also run as a Windows service. For details, see
Start MongoDB Community Edition as a Windows Service. To install MongoDB, see Install MongoDB.
The following examples assume the directory containing the
mongod process is in your system paths. The mongod process is the primary database process that runs on an individual server. mongos
provides a coherent MongoDB interface equivalent to a mongod from the perspective of a client. The mongosh binary provides the administrative shell.
This document discusses the
mongod process; however, some portions of this document may be applicable to mongos instances.
By default, MongoDB listens for connections from clients on port 27017, and stores data in the /data/db directory.
On Windows, this path is
on the drive from which you start MongoDB. For example, if you do not specify a --dbpath, starting a MongoDB server on the C:\ drive stores all data files in C:\data\db.
To start MongoDB using all defaults, issue the following command at the system shell:
If you want
mongod to store data files at a path other than /data/db you can specify a dbPath. The dbPath must exist
before you start mongod. If it does not exist, create the directory and the permissions so that mongod can read and write data to this path. For more information on permissions, see the
security operations documentation.
To specify a dbPath for mongod to use as a data directory, use the
--dbpath option. The following invocation will start a mongod instance and store data in the /srv/mongodb path
mongod --dbpath /srv/mongodb/
Only a single process can listen for connections on a network interface at a time. If you run multiple
mongod processes on a single machine, or have other processes that must use this port, you must assign each a different port to listen on for client connections.
To specify a port to mongod, use the
--port option on the command line. The following command starts mongod listening on port 12345:
Use the default port number when possible, to avoid confusion.
To run a
mongod process as a daemon [i.e. fork], and write its output to a log file, use the --fork and
--logpath options. You must create the log directory; however, mongod will create the log file if it does not exist.
The following command starts
mongod as a daemon and records log output to /var/log/mongodb/mongod.log.
mongod --fork --logpath /var/log/mongodb/mongod.log
For an overview of common configurations and deployments for common use cases, see Run-time Database Configuration.
In a clean shutdown a
mongod completes all pending operations, flushes all data to data files, and closes all data files. Other shutdowns are unclean and can compromise the validity of the data files.
To ensure a clean shutdown, always shutdown mongod instances using
one of the following methods:
Shut down the mongod from mongosh using the db.shutdownServer[] method
as follows:
use admin db.shutdownServer[]
Calling the same method from a init script accomplishes the same result.
For systems with authorization enabled, users may only issue
db.shutdownServer[] when authenticated to the admin database or via the localhost interface on systems without authentication enabled.
Supported on Linux only. From the command line, shut down the mongod using the
--shutdown option:
When running the mongod instance in interactive mode [i.e. without --fork], issue Control-C to
perform a clean shutdown.
Supported on Linux and macOS only. From the command line, shut down a specific mongod instance using one of the following commands:
kill kill -2
Starting in MongoDB 4.0.8 [and 3.6.15], if a replica set primary receives a SIGTERM, the primary attempts to step down before shutting down.
If the step down succeeds, the instance does not vote in the ensuing election of the new primary, and continues its shutdown.
If the step down fails, the instance continues its shutdown.
Warning
Never use kill -9 [i.e. SIGKILL] to terminate a mongod instance.
Starting in MongoDB 4.4 running on Linux:
When the
mongodandmongosprocesses receive aSIGUSR2signal, backtrace details are added to the logs for each process thread.Backtrace details show the function calls for the process, which can be used for diagnostics and provided to MongoDB Support if required.
The backtrace functionality is available for these architectures:
x86_64arm64[starting in MongoDB 4.4.15, 5.0.10, and 6.0]
To issue a SIGUSR2 signal to a running mongod process, use the following command:
kill -SIGUSR2
The resulting backtrace data is written to the
mongod logfile as configured with --logpath
If the mongod is the
primary in a replica set, the shutdown process for this mongod instance has the following steps:
Check how up-to-date the secondaries are.
If no secondary is within 10 seconds of the primary,
mongodwill return a message that it will not shut down. You can pass theshutdowncommand atimeoutSecsargument to wait for a secondary to catch up.If there is a secondary within 10 seconds of the primary, the primary will step down and wait for the secondary to catch up.
After 60 seconds or once the secondary has caught up, the primary will shut down.
If there is no up-to-date
secondary and you want the primary to shut down, issue the shutdown command with the force argument, as in the following mongosh operation:
db.adminCommand[{shutdown : 1, force : true}]
To keep checking the secondaries for a specified number of
seconds if none are immediately up-to-date, issue shutdown with the timeoutSecs argument. MongoDB will keep checking the secondaries for the specified number of seconds if none are immediately up-to-date. If any of the secondaries catch up within the allotted time, the primary will shut down. If no secondaries catch up, it will not shut down.
The following command
issues shutdown with timeoutSecs set to 5:
db.adminCommand[{shutdown : 1, timeoutSecs : 5}]
Alternately you can use the timeoutSecs argument with the db.shutdownServer[] method:
db.shutdownServer[{timeoutSecs : 5}]