# [MongoDB](http://www.mongodb.org)

## FAQ: How to "vacuum" or "compact" a database?

Deleted documents are not removed from disk.  Use the `repairDatabase()`
command to reclaim this space:

    $ mongo mydb
    > db.repairDatabase()
    
Note:

  * This is a blocking operation.
  * It (temporarily) requires at least as much space as the database itself
    to run.  (See below for how to dump/restore if you need to workaround this.)

## HOWTO: Delete (drop) a database?

    $ mongo beebo_dev
    > db.dropDatabase()

## FAQ: How to backup and restore a database?

Backup (mongodb needs to be running):

    # creates "backup" directory, backs up all databases managed by MongoDB
    $ sudo mongodump -o backup
    
Restore (mongodb needs to be running):

    # restore
    $ sudo mongorestore backup
    
If you are dumping and restoring so you're able to `db.repairDatabase()`
(which temporarily requires twice the size of the database itself) follow
these steps:

    # backup as above
    $ sudo mongodump -o backup

    # stop the server
    $ sudo stop mongodb
    
    # delete database files
    
    # restart the server
    $ sudo start mongodb
    
    # restore as above
    $ sudo mongorestore backup

See [backups](http://www.mongodb.org/display/DOCS/Backups).
  
## FAQ: What's the difference between `mongodump` and `mongoexport`?

It seems that the only real difference is output file format; see
[SERVER-203](http://jira.mongodb.org/browse/SERVER-203).  (`mongorestore`
reads the `mongodump` format.)