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.logfile.size 10000000 The max size of each log file hadoop.logfile.count 10 The max number of log files hadoop.job.history.location If job tracker is static the history files are stored in this single well known place. If No value is set here, by default, it is in the local file system at ${hadoop.log.dir}/history. hadoop.job.history.user.location User can specify a location to store the history files of a particular job. If nothing is specified, the logs are stored in output directory. The files are stored in "_logs/history/" in the directory. User can stop logging by giving the value "none". dfs.namenode.logging.level info The logging level for dfs namenode. Other values are "dir"(trac e namespace mutations), "block"(trace block under/over replications and block creations/deletions), or "all". io.sort.factor 10 The number of streams to merge at once while sorting files. This determines the number of open file handles. io.sort.mb 100 The total amount of buffer memory to use while sorting files, in megabytes. By default, gives each merge stream 1MB, which should minimize seeks. io.sort.record.percent 0.05 The percentage of io.sort.mb dedicated to tracking record boundaries. Let this value be r, io.sort.mb be x. The maximum number of records collected before the collection thread must block is equal to (r * x) / 4 io.sort.spill.percent 0.80 The soft limit in either the buffer or record collection buffers. Once reached, a thread will begin to spill the contents to disk in the background. Note that this does not imply any chunking of data to the spill. A value less than 0.5 is not recommended. 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.map.index.skip 0 Number of index entries to skip between each entry. Zero by default. Setting this to values larger than zero can facilitate opening large map files using less memory. io.compression.codecs org.apache.hadoop.io.compress.DefaultCodec,org.apache.hadoop.io.compress.GzipCodec 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.dfs.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.dfs.HftpFileSystem fs.hsftp.impl org.apache.hadoop.dfs.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.inmemory.size.mb 75 The size of the in-memory filsystem instance in MB fs.checkpoint.dir ${hadoop.tmp.dir}/dfs/namesecondary Determines where on the local filesystem the DFS secondary name node should store the temporary images and edits 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.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. dfs.secondary.http.address 0.0.0.0:50090 The secondary namenode http server address and port. If the port is 0 then the server will start on a free port. dfs.datanode.address 0.0.0.0:50010 The address where the datanode server will listen to. If the port is 0 then the server will start on a free port. dfs.datanode.http.address 0.0.0.0:50075 The datanode http server address and port. If the port is 0 then the server will start on a free port. dfs.datanode.ipc.address 0.0.0.0:50020 The datanode ipc server address and port. If the port is 0 then the server will start on a free port. dfs.datanode.handler.count 3 The number of server threads for the datanode. dfs.http.address 0.0.0.0:50070 The address and the base port where the dfs namenode web ui will listen on. If the port is 0 then the server will start on a free port. dfs.datanode.https.address 0.0.0.0:50475 dfs.https.address 0.0.0.0:50470 https.keystore.info.rsrc sslinfo.xml The name of the resource from which ssl keystore information will be extracted dfs.datanode.dns.interface default The name of the Network Interface from which a data node should report its IP address. dfs.datanode.dns.nameserver default The host name or IP address of the name server (DNS) which a DataNode should use to determine the host name used by the NameNode for communication and display purposes. dfs.replication.considerLoad true Decide if chooseTarget considers the target's load or not dfs.default.chunk.view.size 32768 The number of bytes to view for a file on the browser. dfs.datanode.du.reserved 0 Reserved space in bytes per volume. Always leave this much space free for non dfs use. dfs.datanode.du.pct 0.98f When calculating remaining space, only use this percentage of the real available space dfs.name.dir ${hadoop.tmp.dir}/dfs/name Determines where on the local filesystem the DFS name node should store the name table. If this is a comma-delimited list of directories then the name table is replicated in all of the directories, for redundancy. dfs.web.ugi webuser,webgroup The user account used by the web interface. Syntax: USERNAME,GROUP1,GROUP2, ... dfs.permissions true If "true", enable permission checking in HDFS. If "false", permission checking is turned off, but all other behavior is unchanged. Switching from one parameter value to the other does not change the mode, owner or group of files or directories. dfs.permissions.supergroup supergroup The name of the group of super-users. dfs.client.buffer.dir ${hadoop.tmp.dir}/dfs/tmp Determines where on the local filesystem an DFS client should store its blocks before it sends them to the datanode. dfs.data.dir ${hadoop.tmp.dir}/dfs/data Determines where on the local filesystem an DFS data node should store its blocks. If this is a comma-delimited list of directories, then data will be stored in all named directories, typically on different devices. Directories that do not exist are ignored. dfs.replication 3 Default block replication. The actual number of replications can be specified when the file is created. The default is used if replication is not specified in create time. dfs.replication.max 512 Maximal block replication. dfs.replication.min 1 Minimal block replication. dfs.block.size 67108864 The default block size for new files. dfs.df.interval 60000 Disk usage statistics refresh interval in msec. dfs.client.block.write.retries 3 The number of retries for writing blocks to the data nodes, before we signal failure to the application. dfs.blockreport.intervalMsec 3600000 Determines block reporting interval in milliseconds. dfs.blockreport.initialDelay 0 Delay for first block report in seconds. dfs.heartbeat.interval 3 Determines datanode heartbeat interval in seconds. dfs.namenode.handler.count 10 The number of server threads for the namenode. dfs.safemode.threshold.pct 0.999f Specifies the percentage of blocks that should satisfy the minimal replication requirement defined by dfs.replication.min. Values less than or equal to 0 mean not to start in safe mode. Values greater than 1 will make safe mode permanent. dfs.safemode.extension 30000 Determines extension of safe mode in milliseconds after the threshold level is reached. dfs.balance.bandwidthPerSec 1048576 Specifies the maximum amount of bandwidth that each datanode can utilize for the balancing purpose in term of the number of bytes per second. dfs.hosts Names a file that contains a list of hosts that are permitted to connect to the namenode. The full pathname of the file must be specified. If the value is empty, all hosts are permitted. dfs.hosts.exclude Names a file that contains a list of hosts that are not permitted to connect to the namenode. The full pathname of the file must be specified. If the value is empty, no hosts are excluded. dfs.max.objects 0 The maximum number of files, directories and blocks dfs supports. A value of zero indicates no limit to the number of objects that dfs supports. dfs.namenode.decommission.interval 30 Namenode periodicity in seconds to check if decommission is complete. dfs.namenode.decommission.nodes.per.interval 5 The number of nodes namenode checks if decommission is complete in each dfs.namenode.decommission.interval. dfs.replication.interval 3 The periodicity in seconds with which the namenode computes repliaction work for datanodes. 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. mapred.job.tracker local The host and port that the MapReduce job tracker runs at. If "local", then jobs are run in-process as a single map and reduce task. mapred.job.tracker.http.address 0.0.0.0:50030 The job tracker http server address and port the server will listen on. If the port is 0 then the server will start on a free port. mapred.job.tracker.handler.count 10 The number of server threads for the JobTracker. This should be roughly 4% of the number of tasktracker nodes. mapred.task.tracker.report.address 127.0.0.1:0 The interface and port that task tracker server listens on. Since it is only connected to by the tasks, it uses the local interface. EXPERT ONLY. Should only be changed if your host does not have the loopback interface. mapred.local.dir ${hadoop.tmp.dir}/mapred/local The local directory where MapReduce stores intermediate data files. May be a comma-separated list of directories on different devices in order to spread disk i/o. Directories that do not exist are ignored. local.cache.size 10737418240 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. mapred.system.dir ${hadoop.tmp.dir}/mapred/system The shared directory where MapReduce stores control files. mapred.temp.dir ${hadoop.tmp.dir}/mapred/temp A shared directory for temporary files. mapred.local.dir.minspacestart 0 If the space in mapred.local.dir drops under this, do not ask for more tasks. Value in bytes. mapred.local.dir.minspacekill 0 If the space in mapred.local.dir drops under this, do not ask more tasks until all the current ones have finished and cleaned up. Also, to save the rest of the tasks we have running, kill one of them, to clean up some space. Start with the reduce tasks, then go with the ones that have finished the least. Value in bytes. mapred.tasktracker.expiry.interval 600000 Expert: The time-interval, in miliseconds, after which a tasktracker is declared 'lost' if it doesn't send heartbeats. mapred.map.tasks 2 The default number of map tasks per job. Typically set to a prime several times greater than number of available hosts. Ignored when mapred.job.tracker is "local". mapred.reduce.tasks 1 The default number of reduce tasks per job. Typically set to a prime close to the number of available hosts. Ignored when mapred.job.tracker is "local". mapred.map.max.attempts 4 Expert: The maximum number of attempts per map task. In other words, framework will try to execute a map task these many number of times before giving up on it. mapred.reduce.max.attempts 4 Expert: The maximum number of attempts per reduce task. In other words, framework will try to execute a reduce task these many number of times before giving up on it. mapred.reduce.parallel.copies 5 The default number of parallel transfers run by reduce during the copy(shuffle) phase. mapred.reduce.copy.backoff 300 The maximum amount of time (in seconds) a reducer spends on fetching one map output before declaring it as failed. mapred.task.timeout 600000 The number of milliseconds before a task will be terminated if it neither reads an input, writes an output, nor updates its status string. mapred.tasktracker.map.tasks.maximum 2 The maximum number of map tasks that will be run simultaneously by a task tracker. mapred.tasktracker.reduce.tasks.maximum 2 The maximum number of reduce tasks that will be run simultaneously by a task tracker. mapred.jobtracker.completeuserjobs.maximum 100 The maximum number of complete jobs per user to keep around before delegating them to the job history. mapred.child.java.opts -Xmx200m Java opts for the task tracker child processes. The following symbol, if present, will be interpolated: @taskid@ is replaced by current TaskID. Any other occurrences of '@' will go unchanged. For example, to enable verbose gc logging to a file named for the taskid in /tmp and to set the heap maximum to be a gigabyte, pass a 'value' of: -Xmx1024m -verbose:gc -Xloggc:/tmp/@taskid@.gc The configuration variable mapred.child.ulimit can be used to control the maximum virtual memory of the child processes. mapred.child.ulimit The maximum virtual memory, in KB, of a process launched by the Map-Reduce framework. This can be used to control both the Mapper/Reducer tasks and applications using Hadoop Pipes, Hadoop Streaming etc. By default it is left unspecified to let cluster admins control it via limits.conf and other such relevant mechanisms. Note: mapred.child.ulimit must be greater than or equal to the -Xmx passed to JavaVM, else the VM might not start. mapred.child.tmp ./tmp To set the value of tmp directory for map and reduce tasks. If the value is an absolute path, it is directly assigned. Otherwise, it is prepended with task's working directory. The java tasks are executed with option -Djava.io.tmpdir='the absolute path of the tmp dir'. Pipes and streaming are set with environment variable, TMPDIR='the absolute path of the tmp dir' mapred.inmem.merge.threshold 1000 The threshold, in terms of the number of files for the in-memory merge process. When we accumulate threshold number of files we initiate the in-memory merge and spill to disk. A value of 0 or less than 0 indicates we want to DON'T have any threshold and instead depend only on the ramfs's memory consumption to trigger the merge. mapred.map.tasks.speculative.execution true If true, then multiple instances of some map tasks may be executed in parallel. mapred.reduce.tasks.speculative.execution true If true, then multiple instances of some reduce tasks may be executed in parallel. mapred.min.split.size 0 The minimum size chunk that map input should be split into. Note that some file formats may have minimum split sizes that take priority over this setting. mapred.submit.replication 10 The replication level for submitted job files. This should be around the square root of the number of nodes. mapred.tasktracker.dns.interface default The name of the Network Interface from which a task tracker should report its IP address. mapred.tasktracker.dns.nameserver default The host name or IP address of the name server (DNS) which a TaskTracker should use to determine the host name used by the JobTracker for communication and display purposes. tasktracker.http.threads 40 The number of worker threads that for the http server. This is used for map output fetching mapred.task.tracker.http.address 0.0.0.0:50060 The task tracker http server address and port. If the port is 0 then the server will start on a free port. keep.failed.task.files false Should the files for failed tasks be kept. This should only be used on jobs that are failing, because the storage is never reclaimed. It also prevents the map outputs from being erased from the reduce directory as they are consumed. mapred.output.compress false Should the job outputs be compressed? mapred.output.compression.type RECORD If the job outputs are to compressed as SequenceFiles, how should they be compressed? Should be one of NONE, RECORD or BLOCK. mapred.output.compression.codec org.apache.hadoop.io.compress.DefaultCodec If the job outputs are compressed, how should they be compressed? mapred.compress.map.output false Should the outputs of the maps be compressed before being sent across the network. Uses SequenceFile compression. mapred.map.output.compression.codec org.apache.hadoop.io.compress.DefaultCodec If the map outputs are compressed, how should they be compressed? 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 map.sort.class org.apache.hadoop.util.QuickSort The default sort class for sorting keys. mapred.userlog.limit.kb 0 The maximum size of user-logs of each task in KB. 0 disables the cap. mapred.userlog.retain.hours 24 The maximum time, in hours, for which the user-logs are to be retained. mapred.hosts Names a file that contains the list of nodes that may connect to the jobtracker. If the value is empty, all hosts are permitted. mapred.hosts.exclude Names a file that contains the list of hosts that should be excluded by the jobtracker. If the value is empty, no hosts are excluded. mapred.max.tracker.failures 4 The number of task-failures on a tasktracker of a given job after which new tasks of that job aren't assigned to it. jobclient.output.filter FAILED The filter for controlling the output of the task's userlogs sent to the console of the JobClient. The permissible options are: NONE, KILLED, FAILED, SUCCEEDED and ALL. mapred.job.tracker.persist.jobstatus.active false Indicates if persistency of job status information is active or not. mapred.job.tracker.persist.jobstatus.hours 0 The number of hours job status information is persisted in DFS. The job status information will be available after it drops of the memory queue and between jobtracker restarts. With a zero value the job status information is not persisted at all in DFS. mapred.job.tracker.persist.jobstatus.dir /jobtracker/jobsInfo The directory where the job status information is persisted in a file system to be available after it drops of the memory queue and between jobtracker restarts. mapred.task.profile false To set whether the system should collect profiler information for some of the tasks in this job? The information is stored in the user log directory. The value is "true" if task profiling is enabled. mapred.task.profile.maps 0-2 To set the ranges of map tasks to profile. mapred.task.profile has to be set to true for the value to be accounted. mapred.task.profile.reduces 0-2 To set the ranges of reduce tasks to profile. mapred.task.profile has to be set to true for the value to be accounted. mapred.line.input.format.linespermap 1 Number of lines per split in NLineInputFormat. 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. job.end.retry.attempts 0 Indicates how many times hadoop should attempt to contact the notification URL job.end.retry.interval 30000 Indicates time in milliseconds between notification URL retry calls 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.rpc.socket.factory.class.JobSubmissionProtocol SocketFactory to use to connect to a Map/Reduce master (JobTracker). If null or empty, then use hadoop.rpc.socket.class.default. 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 20 The max number of args that the script configured with topology.script.file.name should be run with. Each arg is an IP address. mapred.task.cache.levels 2 This is the max level of the task cache. For example, if the level is 2, the tasks cached are at the host level and at the rack level. mapred.merge.recordsBeforeProgress 10000 The number of records to process during merge before sending a progress notification to the TaskTracker.