单个collection备份：
mongoexport -h dbhost -d dbname -c collectionname -f collectionKey -o file
-h: MongoDB所在服务器地址
-d: 需要恢复的数据库实例
-c: 需要恢复的集合
-f: 需要导出的字段(省略为所有字段)
-o: 表示导出的文件名
单个collection恢复：
mongoimport -d dbhost -c collectionname –type csv –headerline –file
-type: 指明要导入的文件格式
-headerline: 批明不导入第一行，因为第一行是列名
-file: 指明要导入的文件路径
[root@mongodb02 mongodb]# mongoexport --help
Usage:
mongoexport <options>
Export data from MongoDB in CSV or JSON format.
See http://docs.mongodb.org/manual/reference/program/mongoexport/ for more information.
general options:
--help print usage
--version print the tool version and exit
verbosity options:
-v, --verbose=<level> more detailed log output (include multiple times for more verbosity, e.g. -vvvvv, or specify a numeric value, e.g. --verbose=N)
--quiet hide all log output
connection options:
-h, --host=<hostname> mongodb host to connect to (setname/host1,host2 for replica sets)
--port=<port> server port (can also use --host hostname:port)
ssl options:
--ssl connect to a mongod or mongos that has ssl enabled
--sslCAFile=<filename> the .pem file containing the root certificate chain from the certificate authority
--sslPEMKeyFile=<filename> the .pem file containing the certificate and key
--sslPEMKeyPassword=<password> the password to decrypt the sslPEMKeyFile, if necessary
--sslCRLFile=<filename> the .pem file containing the certificate revocation list
--sslAllowInvalidCertificates bypass the validation for server certificates
--sslAllowInvalidHostnames bypass the validation for server name
--sslFIPSMode use FIPS mode of the installed openssl library
authentication options:
-u, --username=<username> username for authentication
-p, --password=<password> password for authentication
--authenticationDatabase=<database-name> database that holds the user's credentials
--authenticationMechanism=<mechanism> authentication mechanism to use
namespace options:
-d, --db=<database-name> database to use
-c, --collection=<collection-name> collection to use
uri options:
--uri=mongodb-uri mongodb uri connection string
output options:
-f, --fields=<field>[,<field>]* comma separated list of field names (required for exporting CSV) e.g. -f "name,age"
--fieldFile=<filename> file with field names - 1 per line
--type=<type> the output format, either json or csv (defaults to 'json') (default: json)
-o, --out=<filename> output file; if not specified, stdout is used
--jsonArray output to a JSON array rather than one object per line
--pretty output JSON formatted to be human-readable
--noHeaderLine export CSV data without a list of field names at the first line
querying options:
-q, --query=<json> query filter, as a JSON string, e.g., '{x:{$gt:1}}'
--queryFile=<filename> path to a file containing a query filter (JSON)
-k, --slaveOk allow secondary reads if available (default true) (default: false)
--readPreference=<string>|<json> specify either a preference name or a preference json object
--forceTableScan force a table scan (do not use $snapshot)
--skip=<count> number of documents to skip
--limit=<count> limit the number of documents to export
--sort=<json> sort order, as a JSON string, e.g. '{x:1}'
--assertExists if specified, export fails if the collection does not exist (default: false)
