# MongoDB

MongoDB (from humongous) is an open source document-oriented database system developed and supported by MongoDB Inc. (formerly 10gen). It is part of the NoSQL family of database systems. Instead of storing data in tables as is done in a "classical" relational database, MongoDB stores structured data as JSON-like documents with dynamic schemas (MongoDB calls the format BSON), making the integration of data in certain types of applications easier and faster.

## Installation

The factual accuracy of this article or section is disputed.

Reason: The space and time for the pre-allocation is incorrect or outdated, on a recent install it pre-allocated 300 M apparent-size and only 222 K of disk space (Discuss in Talk:MongoDB#Installation space/time)

Install mongodb from official repositories.

Start/Enable the `mongodb.service` daemon.

During the first startup of the mongodb service, it will pre-allocate space, by creating large files (for its journal and other data). These files may take up a total space of 3 GB.

Please note this step may take a while, during which the database shell is unavailable.

## Usage

To access the Database shell type in the terminal:

    $ mongo

## Troubleshooting

### MongoDB won't start

Check that there is at least 3GB space available for its journal files, otherwise mongodb can fail to start (without issuing a message to the user):

    $ df -h /var/lib/mongodb/

Check if the lock file exists:

    # ls  -lisa /var/lib/mongodb

If it does, stop `mongodb.service`, and delete the file. Then start the service again.

    # rm /var/lib/mongodb/mongod.lock

If it still won't start, run a repair on the database, specifying the dbpath (/var/lib/mongodb/ is the default --dbpath in Arch Linux):

    # mongod --dbpath /var/lib/mongodb/ --repair

After running the repair as root, the files will be owned by the root user, whilst Arch Linux runs it under a different user. You will need to use chown to change the ownership of the files back to the correct user. See following link for further details: Further reference

    # chown -R mongodb: /var/{log,lib}/mongodb/

Check that the boost-libs package is up to date. MongoDB requires a specific version, however, the package does not restrict the version of this dependency.

Category:

- Database management systems

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