core-default配置说明等

为了以后查找方便，故将配置说明等列在这里

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<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>

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<!-- wish to modify from this file into core-site.xml and change them -->
<!-- there.  If core-site.xml does not already exist, create it.      -->

<configuration>

<!--- global properties -->

<property>
  <name>hadoop.tmp.dir</name>
  <value>/tmp/hadoop-${user.name}</value>
  <description>A base for other temporary directories.</description>
</property>

<property>
  <name>hadoop.native.lib</name>
  <value>true</value>
  <description>Should native hadoop libraries, if present, be used.</description>
</property>

<property>
  <name>hadoop.http.filter.initializers</name>
  <value></value>
  <description>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.</description>
</property>

<property>
  <name>hadoop.security.authorization</name>
  <value>false</value>
  <description>Is service-level authorization enabled?</description>
</property>

<!--- logging properties -->

<property>
  <name>hadoop.logfile.size</name>
  <value>10000000</value>
  <description>The max size of each log file</description>
</property>

<property>
  <name>hadoop.logfile.count</name>
  <value>10</value>
  <description>The max number of log files</description>
</property>

<!-- i/o properties -->
<property>
  <name>io.file.buffer.size</name>
  <value>4096</value>
  <description>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.</description>
</property>
  
<property>
  <name>io.bytes.per.checksum</name>
  <value>512</value>
  <description>The number of bytes per checksum.  Must not be larger than
  io.file.buffer.size.</description>
</property>

<property>
  <name>io.skip.checksum.errors</name>
  <value>false</value>
  <description>If true, when a checksum error is encountered while
  reading a sequence file, entries are skipped, instead of throwing an
  exception.</description>
</property>

<property>
  <name>io.compression.codecs</name>
  <value>org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec,org.apache.hadoop.io.compress.BZip2Codec</value>
  <description>A list of the compression codec classes that can be used 
               for compression/decompression.</description>
</property>

<property>
  <name>io.serializations</name>
  <value>org.apache.hadoop.io.serializer.WritableSerialization</value>
  <description>A list of serialization classes that can be used for
  obtaining serializers and deserializers.</description>
</property>

<!-- file system properties -->

<property>
  <name>fs.default.name</name>
  <value>file:///</value>
  <description>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.</description>
</property>

<property>
  <name>fs.trash.interval</name>
  <value>0</value>
  <description>Number of minutes between trash checkpoints.
  If zero, the trash feature is disabled.
  </description>
</property>

<property>
  <name>fs.file.impl</name>
  <value>org.apache.hadoop.fs.LocalFileSystem</value>
  <description>The FileSystem for file: uris.</description>
</property>

<property>
  <name>fs.hdfs.impl</name>
  <value>org.apache.hadoop.hdfs.DistributedFileSystem</value>
  <description>The FileSystem for hdfs: uris.</description>
</property>

<property>
  <name>fs.s3.impl</name>
  <value>org.apache.hadoop.fs.s3.S3FileSystem</value>
  <description>The FileSystem for s3: uris.</description>
</property>

<property>
  <name>fs.s3n.impl</name>
  <value>org.apache.hadoop.fs.s3native.NativeS3FileSystem</value>
  <description>The FileSystem for s3n: (Native S3) uris.</description>
</property>

<property>
  <name>fs.kfs.impl</name>
  <value>org.apache.hadoop.fs.kfs.KosmosFileSystem</value>
  <description>The FileSystem for kfs: uris.</description>
</property>

<property>
  <name>fs.hftp.impl</name>
  <value>org.apache.hadoop.hdfs.HftpFileSystem</value>
</property>

<property>
  <name>fs.hsftp.impl</name>
  <value>org.apache.hadoop.hdfs.HsftpFileSystem</value>
</property>

<property>
  <name>fs.ftp.impl</name>
  <value>org.apache.hadoop.fs.ftp.FTPFileSystem</value>
  <description>The FileSystem for ftp: uris.</description>
</property>

<property>
  <name>fs.ramfs.impl</name>
  <value>org.apache.hadoop.fs.InMemoryFileSystem</value>
  <description>The FileSystem for ramfs: uris.</description>
</property>

<property>
  <name>fs.har.impl</name>
  <value>org.apache.hadoop.fs.HarFileSystem</value>
  <description>The filesystem for Hadoop archives. </description>
</property>

<property>
  <name>fs.har.impl.disable.cache</name>
  <value>true</value>
  <description>Don't cache 'har' filesystem instances.</description>
</property>

<property>
  <name>fs.checkpoint.dir</name>
  <value>${hadoop.tmp.dir}/dfs/namesecondary</value>
  <description>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.
  </description>
</property>

<property>
  <name>fs.checkpoint.edits.dir</name>
  <value>${fs.checkpoint.dir}</value>
  <description>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
  </description>
</property>

<property>
  <name>fs.checkpoint.period</name>
  <value>3600</value>
  <description>The number of seconds between two periodic checkpoints.
  </description>
</property>

<property>
  <name>fs.checkpoint.size</name>
  <value>67108864</value>
  <description>The size of the current edit log (in bytes) that triggers
       a periodic checkpoint even if the fs.checkpoint.period hasn't expired.
  </description>
</property>



<property>
  <name>fs.s3.block.size</name>
  <value>67108864</value>
  <description>Block size to use when writing files to S3.</description>
</property>

<property>
  <name>fs.s3.buffer.dir</name>
  <value>${hadoop.tmp.dir}/s3</value>
  <description>Determines where on the local filesystem the S3 filesystem
  should store files before sending them to S3
  (or after retrieving them from S3).
  </description>
</property>

<property>
  <name>fs.s3.maxRetries</name>
  <value>4</value>
  <description>The maximum number of retries for reading or writing files to S3, 
  before we signal failure to the application.
  </description>
</property>

<property>
  <name>fs.s3.sleepTimeSeconds</name>
  <value>10</value>
  <description>The number of seconds to sleep between each S3 retry.
  </description>
</property>


<property>
  <name>local.cache.size</name>
  <value>10737418240</value>
  <description>The limit on the size of cache you want to keep, set by default
  to 10GB. This will act as a soft limit on the cache directory for out of band data.
  </description>
</property>
            
<property>
  <name>io.seqfile.compress.blocksize</name>
  <value>1000000</value>
  <description>The minimum block size for compression in block compressed 
          SequenceFiles.
  </description>
</property>

<property>
  <name>io.seqfile.lazydecompress</name>
  <value>true</value>
  <description>Should values of block-compressed SequenceFiles be decompressed
          only when necessary.
  </description>
</property>

<property>
  <name>io.seqfile.sorter.recordlimit</name>
  <value>1000000</value>
  <description>The limit on number of records to be kept in memory in a spill 
          in SequenceFiles.Sorter
  </description>
</property>

 <property>
  <name>io.mapfile.bloom.size</name>
  <value>1048576</value>
  <description>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.
  </description>
</property>

<property>
  <name>io.mapfile.bloom.error.rate</name>
  <value>0.005</value>
  <description>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%).
  </description>
</property>

<property>
  <name>hadoop.util.hash.type</name>
  <value>murmur</value>
  <description>The default implementation of Hash. Currently this can take one of the
  two values: 'murmur' to select MurmurHash and 'jenkins' to select JenkinsHash.
  </description>
</property>


<!-- ipc properties -->

<property>
  <name>ipc.client.idlethreshold</name>
  <value>4000</value>
  <description>Defines the threshold number of connections after which
               connections will be inspected for idleness.
  </description>
</property>

<property>
  <name>ipc.client.kill.max</name>
  <value>10</value>
  <description>Defines the maximum number of clients to disconnect in one go.
  </description>
</property>

<property>
  <name>ipc.client.connection.maxidletime</name>
  <value>10000</value>
  <description>The maximum time in msec after which a client will bring down the
               connection to the server.
  </description>
</property>

<property>
  <name>ipc.client.connect.max.retries</name>
  <value>10</value>
  <description>Indicates the number of retries a client will make to establish
               a server connection.
  </description>
</property>

<property>
  <name>ipc.server.listen.queue.size</name>
  <value>128</value>
  <description>Indicates the length of the listen queue for servers accepting
               client connections.
  </description>
</property>

<property>
  <name>ipc.server.tcpnodelay</name>
  <value>false</value>
  <description>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. 
  </description>
</property>

<property>
  <name>ipc.client.tcpnodelay</name>
  <value>false</value>
  <description>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. 
  </description>
</property>


<!-- Web Interface Configuration -->

<property>
  <name>webinterface.private.actions</name>
  <value>false</value>
  <description> 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.
  </description>
</property>

<!-- Proxy Configuration -->

<property>
  <name>hadoop.rpc.socket.factory.class.default</name>
  <value>org.apache.hadoop.net.StandardSocketFactory</value>
  <description> Default SocketFactory to use. This parameter is expected to be
    formatted as "package.FactoryClassName".
  </description>
</property>

<property>
  <name>hadoop.rpc.socket.factory.class.ClientProtocol</name>
  <value></value>
  <description> 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.
  </description>
</property>



<property>
  <name>hadoop.socks.server</name>
  <value></value>
  <description> Address (host:port) of the SOCKS server to be used by the
    SocksSocketFactory.
  </description>
</property>

<!-- Rack Configuration -->

<property>
  <name>topology.node.switch.mapping.impl</name>
  <value>org.apache.hadoop.net.ScriptBasedMapping</value>
  <description> 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.
  </description>
</property>

<property>
  <name>topology.script.file.name</name>
  <value></value>
  <description> 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.
  </description>
</property>

<property>
  <name>topology.script.number.args</name>
  <value>100</value>
  <description> The max number of args that the script configured with 
    topology.script.file.name should be run with. Each arg is an
    IP address.
  </description>
</property>



</configuration>