name | value | description
hadoop.tmp.dir | /tmp/hadoop-${user.name} | A base for other temporary directories.
hadoop.native.lib | true | Should native hadoop libraries, if present, be used.
hadoop.http.filter.initializers |  | A comma separated list of class names. Each class in the list must extend org.apache.hadoop.http.FilterInitializer. The corresponding Filter will be initialized. Then, the Filter will be applied to all user facing jsp and servlet web pages. The ordering of the list defines the ordering of the filters.
hadoop.security.group.mapping | org.apache.hadoop.security.ShellBasedUnixGroupsMapping | Class for user to group mapping (get groups for a given user)
hadoop.security.authorization | false | Is service-level authorization enabled?
hadoop.security.authentication | simple | Possible values are simple (no authentication), and kerberos
hadoop.workaround.non.threadsafe.getpwuid | false | Some operating systems or authentication modules are known to have broken implementations of getpwuid_r and getpwgid_r, such that these calls are not thread-safe. Symptoms of this problem include JVM crashes with a stack trace inside these functions. If your system exhibits this issue, enable this configuration parameter to include a lock around the calls as a workaround. An incomplete list of some systems known to have this issue is available at http://wiki.apache.org/hadoop/KnownBrokenPwuidImplementations
hadoop.kerberos.kinit.command | kinit | Used to periodically renew Kerberos credentials when provided to Hadoop. The default setting assumes that kinit is in the PATH of users running the Hadoop client. Change this to the absolute path to kinit if this is not the case.
hadoop.logfile.size | 10000000 | The max size of each log file
hadoop.logfile.count | 10 | The max number of log files
io.file.buffer.size | 4096 | The size of buffer for use in sequence files. The size of this buffer should probably be a multiple of hardware page size (4096 on Intel x86), and it determines how much data is buffered during read and write operations.
io.bytes.per.checksum | 512 | The number of bytes per checksum. Must not be larger than io.file.buffer.size.
io.skip.checksum.errors | false | If true, when a checksum error is encountered while reading a sequence file, entries are skipped, instead of throwing an exception.
io.compression.codecs | org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec,org.apache.hadoop.io.compress.DeflateCodec,org.apache.hadoop.io.compress.SnappyCodec | A list of the compression codec classes that can be used for compression/decompression.
io.serializations | org.apache.hadoop.io.serializer.WritableSerialization | A list of serialization classes that can be used for obtaining serializers and deserializers.
fs.default.name | file:/// | The name of the default file system. A URI whose scheme and authority determine the FileSystem implementation. The uri's scheme determines the config property (fs.SCHEME.impl) naming the FileSystem implementation class. The uri's authority is used to determine the host, port, etc. for a filesystem.
fs.trash.interval | 0 | Number of minutes between trash checkpoints. If zero, the trash feature is disabled.
fs.file.impl | org.apache.hadoop.fs.LocalFileSystem | The FileSystem for file: uris.
fs.hdfs.impl | org.apache.hadoop.hdfs.DistributedFileSystem | The FileSystem for hdfs: uris.
fs.s3.impl | org.apache.hadoop.fs.s3.S3FileSystem | The FileSystem for s3: uris.
fs.s3n.impl | org.apache.hadoop.fs.s3native.NativeS3FileSystem | The FileSystem for s3n: (Native S3) uris.
fs.kfs.impl | org.apache.hadoop.fs.kfs.KosmosFileSystem | The FileSystem for kfs: uris.
fs.hftp.impl | org.apache.hadoop.hdfs.HftpFileSystem |
fs.hsftp.impl | org.apache.hadoop.hdfs.HsftpFileSystem |
fs.ftp.impl | org.apache.hadoop.fs.ftp.FTPFileSystem | The FileSystem for ftp: uris.
fs.ramfs.impl | org.apache.hadoop.fs.InMemoryFileSystem | The FileSystem for ramfs: uris.
fs.har.impl | org.apache.hadoop.fs.HarFileSystem | The filesystem for Hadoop archives.
fs.har.impl.disable.cache | true | Don't cache 'har' filesystem instances.
fs.checkpoint.dir | ${hadoop.tmp.dir}/dfs/namesecondary | Determines where on the local filesystem the DFS secondary name node should store the temporary images to merge. If this is a comma-delimited list of directories then the image is replicated in all of the directories for redundancy.
fs.checkpoint.edits.dir | ${fs.checkpoint.dir} | Determines where on the local filesystem the DFS secondary name node should store the temporary edits to merge. If this is a comma-delimited list of directoires then teh edits is replicated in all of the directoires for redundancy. Default value is same as fs.checkpoint.dir
fs.checkpoint.period | 3600 | The number of seconds between two periodic checkpoints.
fs.checkpoint.size | 67108864 | The size of the current edit log (in bytes) that triggers a periodic checkpoint even if the fs.checkpoint.period hasn't expired.
fs.s3.block.size | 67108864 | Block size to use when writing files to S3.
fs.s3.buffer.dir | ${hadoop.tmp.dir}/s3 | Determines where on the local filesystem the S3 filesystem should store files before sending them to S3 (or after retrieving them from S3).
fs.s3.maxRetries | 4 | The maximum number of retries for reading or writing files to S3, before we signal failure to the application.
fs.s3.sleepTimeSeconds | 10 | The number of seconds to sleep between each S3 retry.
fs.automatic.close | true | By default, FileSystem instances are automatically closed at program exit using a JVM shutdown hook. Setting this property to false disables this behavior. This is an advanced option that should only be used by server applications requiring a more carefully orchestrated shutdown sequence.
fs.s3n.block.size | 67108864 | Block size to use when reading files using the native S3 filesystem (s3n: URIs).
io.seqfile.compress.blocksize | 1000000 | The minimum block size for compression in block compressed SequenceFiles.
io.seqfile.lazydecompress | true | Should values of block-compressed SequenceFiles be decompressed only when necessary.
io.seqfile.sorter.recordlimit | 1000000 | The limit on number of records to be kept in memory in a spill in SequenceFiles.Sorter
io.mapfile.bloom.size | 1048576 | The size of BloomFilter-s used in BloomMapFile. Each time this many keys is appended the next BloomFilter will be created (inside a DynamicBloomFilter). Larger values minimize the number of filters, which slightly increases the performance, but may waste too much space if the total number of keys is usually much smaller than this number.
io.mapfile.bloom.error.rate | 0.005 | The rate of false positives in BloomFilter-s used in BloomMapFile. As this value decreases, the size of BloomFilter-s increases exponentially. This value is the probability of encountering false positives (default is 0.5%).
hadoop.util.hash.type | murmur | The default implementation of Hash. Currently this can take one of the two values: 'murmur' to select MurmurHash and 'jenkins' to select JenkinsHash.
ipc.client.idlethreshold | 4000 | Defines the threshold number of connections after which connections will be inspected for idleness.
ipc.client.kill.max | 10 | Defines the maximum number of clients to disconnect in one go.
ipc.client.connection.maxidletime | 10000 | The maximum time in msec after which a client will bring down the connection to the server.
ipc.client.connect.max.retries | 10 | Indicates the number of retries a client will make to establish a server connection.
ipc.server.listen.queue.size | 128 | Indicates the length of the listen queue for servers accepting client connections.
ipc.server.tcpnodelay | false | Turn on/off Nagle's algorithm for the TCP socket connection on the server. Setting to true disables the algorithm and may decrease latency with a cost of more/smaller packets.
ipc.client.tcpnodelay | false | Turn on/off Nagle's algorithm for the TCP socket connection on the client. Setting to true disables the algorithm and may decrease latency with a cost of more/smaller packets.
webinterface.private.actions | false | If set to true, the web interfaces of JT and NN may contain actions, such as kill job, delete file, etc., that should not be exposed to public. Enable this option if the interfaces are only reachable by those who have the right authorization.
hadoop.rpc.socket.factory.class.default | org.apache.hadoop.net.StandardSocketFactory | Default SocketFactory to use. This parameter is expected to be formatted as "package.FactoryClassName".
hadoop.rpc.socket.factory.class.ClientProtocol |  | SocketFactory to use to connect to a DFS. If null or empty, use hadoop.rpc.socket.class.default. This socket factory is also used by DFSClient to create sockets to DataNodes.
hadoop.socks.server |  | Address (host:port) of the SOCKS server to be used by the SocksSocketFactory.
topology.node.switch.mapping.impl | org.apache.hadoop.net.ScriptBasedMapping | The default implementation of the DNSToSwitchMapping. It invokes a script specified in topology.script.file.name to resolve node names. If the value for topology.script.file.name is not set, the default value of DEFAULT_RACK is returned for all node names.
topology.script.file.name |  | The script name that should be invoked to resolve DNS names to NetworkTopology names. Example: the script would take host.foo.bar as an argument, and return /rack1 as the output.
topology.script.number.args | 100 | The max number of args that the script configured with topology.script.file.name should be run with. Each arg is an IP address.
hadoop.security.uid.cache.secs | 14400 | NativeIO maintains a cache from UID to UserName. This is the timeout for an entry in that cache.