Commands useful for administrators of a hadoop cluster.
balancer
Runs a cluster balancing utility. An administrator can simply press Ctrl-C to stop the rebalancing process. See Rebalancer for more details.
Usage: hadoop balancer [-threshold <threshold>]
| COMMAND_OPTION | Description |
|---|---|
| -threshold threshold | Percentage of disk capacity. This overwrites the default threshold. |
daemonlog
Get/Set the log level for each daemon.
Usage: hadoop daemonlog -getlevel <host:port> <name> Usage: hadoop daemonlog -setlevel <host:port> <name> <level>
| COMMAND_OPTION | Description |
|---|---|
| -getlevel host:port name | Prints the log level of the daemon running at host:port. This command internally connects to http://host:port/logLevel?log=name |
| -setlevel host:port name level | Sets the log level of the daemon running at host:port. This command internally connects to http://host:port/logLevel?log=name |
datanode
Runs a HDFS datanode.
Usage: hadoop datanode [-rollback]
| COMMAND_OPTION | Description |
|---|---|
| -rollback | Rollsback the datanode to the previous version. This should be used after stopping the datanode and distributing the old hadoop version. |
dfsadmin
Runs a HDFS dfsadmin client.
Usage: hadoop dfsadmin [GENERIC_OPTIONS] [-report] [-safemode enter | leave | get | wait] [-refreshNodes] [-finalizeUpgrade] [-upgradeProgress status | details | force] [-metasave filename] [-setQuota <quota> <dirname>...<dirname>] [-clrQuota <dirname>...<dirname>] [-restoreFailedStorage true|false|check] [-help [cmd]]
| COMMAND_OPTION | Description |
|---|---|
| -report | Reports basic filesystem information and statistics. |
| -safemode enter / leave / get / wait | Safe mode maintenance command. Safe mode is a Namenode state in which it 1. does not accept changes to the name space (read-only) 2. does not replicate or delete blocks. Safe mode is entered automatically at Namenode startup, and leaves safe mode automatically when the configured minimum percentage of blocks satisfies the minimum replication condition. Safe mode can also be entered manually, but then it can only be turned off manually as well. |
| -refreshNodes | Re-read the hosts and exclude files to update the set of Datanodes that are allowed to connect to the Namenode and those that should be decommissioned or recommissioned. |
| -finalizeUpgrade | Finalize upgrade of HDFS. Datanodes delete their previous version working directories, followed by Namenode doing the same. This completes the upgrade process. |
| -upgradeProgress status / details / force | Request current distributed upgrade status, a detailed status or force the upgrade to proceed. |
| -metasave filename | Save Namenode's primary data structures to filename in the directory specified by hadoop.log.dir property. filename is overwritten if it exists. filename will contain one line for each of the following 1. Datanodes heart beating with Namenode 2. Blocks waiting to be replicated 3. Blocks currrently being replicated 4. Blocks waiting to be deleted |
| -setQuota quota dirname...dirname | Set the quota quota for each directory dirname. The directory quota is a long integer that puts a hard limit on the number of names in the directory tree. Best effort for the directory, with faults reported if 1. N is not a positive integer, or 2. user is not an administrator, or 3. the directory does not exist or is a file, or 4. the directory would immediately exceed the new quota. |
| -clrQuota dirname...dirname | Clear the quota for each directory dirname. Best effort for the directory. with fault reported if 1. the directory does not exist or is a file, or 2. user is not an administrator. It does not fault if the directory has no quota. |
| -restoreFailedStorage true / false / check | This option will turn on/off automatic attempt to restore failed storage replicas. If a failed storage becomes available again the system will attempt to restore edits and/or fsimage during checkpoint. 'check' option will return current setting. |
| -help [cmd] | Displays help for the given command or all commands if none is specified. |
mradmin
Runs MR admin client
Usage: hadoop mradmin [ GENERIC_OPTIONS ] [-refreshQueueAcls]
| COMMAND_OPTION | Description |
|---|---|
| -refreshQueueAcls | Refresh the queue acls used by hadoop, to check access during submissions and administration of the job by the user. The properties present in mapred-queue-acls.xml is reloaded by the queue manager. |
jobtracker
Runs the MapReduce job Tracker node.
Usage: hadoop jobtracker [-dumpConfiguration]
| COMMAND_OPTION | Description |
|---|---|
| -dumpConfiguration | Dumps the configuration used by the JobTracker alongwith queue configuration in JSON format into Standard output used by the jobtracker and exits. |
namenode
Runs the namenode. More info about the upgrade, rollback and finalize is at Upgrade Rollback.
Usage: hadoop namenode [-format] | [-upgrade] | [-rollback] | [-finalize] | [-importCheckpoint]
| COMMAND_OPTION | Description |
|---|---|
| -format | Formats the namenode. It starts the namenode, formats it and then shut it down. |
| -upgrade | Namenode should be started with upgrade option after the distribution of new hadoop version. |
| -rollback | Rollsback the namenode to the previous version. This should be used after stopping the cluster and distributing the old hadoop version. |
| -finalize | Finalize will remove the previous state of the files system. Recent upgrade will become permanent. Rollback option will not be available anymore. After finalization it shuts the namenode down. |
| -importCheckpoint | Loads image from a checkpoint directory and save it into the current one. Checkpoint dir is read from property fs.checkpoint.dir |
secondarynamenode
Runs the HDFS secondary namenode. See Secondary Namenode for more info.
Usage: hadoop secondarynamenode [-checkpoint [force]] | [-geteditsize]
| COMMAND_OPTION | Description |
|---|---|
| -checkpoint [-force] | Checkpoints the Secondary namenode if EditLog size >= fs.checkpoint.size. If -force is used, checkpoint irrespective of EditLog size. |
| -geteditsize | Prints the EditLog size. |
tasktracker
Runs a MapReduce task Tracker node.
Usage: hadoop tasktracker